[PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Peng Tao]

Issuing layoutget at .pg_init will drop the IO size information and ask for 4KB
layout every time. However, the IO size information is very valuable for MDS to
determine how much layout it should return to client.

The patchset try to allow LD not to send layoutget at .pg_init but instead at
pnfs_do_multiple_writes. So that real IO size is preserved and sent to MDS.

Tests against a server that does not aggressively pre-allocate layout, shows
that the IO size informantion is really useful to block layout MDS.

The generic pnfs layer changes are trival to file layout and object as long as
they still send layoutget at .pg_init.

iozone cmd:
./iozone -r 1m -s 4G -w -W -c -t 10 -i 0 -F /mnt/iozone.data.1 /mnt/iozone.data.2 /mnt/iozone.data.3 /mnt/iozone.data.4 /mnt/iozone.data.5 /mnt/iozone.data.6 /mnt/iozone.data.7 /mnt/iozone.data.8 /mnt/iozone.data.9 /mnt/iozone.data.10

Befor patch: around 12MB/s throughput
After patch: around 72MB/s throughput

Peng Tao (4):
  nfsv41: export pnfs_find_alloc_layout
  nfsv41: add and export pnfs_find_get_layout_locked
  nfsv41: get lseg before issue LD IO if pgio doesn't carry lseg
  pnfsblock: do ask for layout in pg_init

 fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++-
 fs/nfs/pnfs.c                    |   74 +++++++++++++++++++++++++++++++++++++-
 fs/nfs/pnfs.h                    |    9 +++++
 3 files changed, 134 insertions(+), 3 deletions(-)

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 12/02/2011 08:52 PM, Peng Tao wrote:
> Issuing layoutget at .pg_init will drop the IO size information and ask for 4KB
> layout every time. However, the IO size information is very valuable for MDS to
> determine how much layout it should return to client.
> 
> The patchset try to allow LD not to send layoutget at .pg_init but instead at
> pnfs_do_multiple_writes. So that real IO size is preserved and sent to MDS.
> 
> Tests against a server that does not aggressively pre-allocate layout, shows
> that the IO size informantion is really useful to block layout MDS.
> 
> The generic pnfs layer changes are trival to file layout and object as long as
> they still send layoutget at .pg_init.
> 

I have a better solution for your problem. Which is a much smaller a change and
I think gives you much better heuristics.

Keep the layout_get exactly where it is, but instead of sending PAGE_SIZE send
the amount of dirty pages you have.

If it is a linear write you will be exact on the money with a single lo_get. If
it is an heavy random write then you might need more lo_gets and you might be getting
some unused segments. But heavy random write is rare and slow anyway. As a first
approximation its fine. (We can later fix that as well)

The .pg_init is done after .write_pages call from VFS and all the to-be-written
pages are already staged to be written. So there should be a way to easily extract
that information.

> iozone cmd:
> ./iozone -r 1m -s 4G -w -W -c -t 10 -i 0 -F /mnt/iozone.data.1 /mnt/iozone.data.2 /mnt/iozone.data.3 /mnt/iozone.data.4 /mnt/iozone.data.5 /mnt/iozone.data.6 /mnt/iozone.data.7 /mnt/iozone.data.8 /mnt/iozone.data.9 /mnt/iozone.data.10
> 
> Befor patch: around 12MB/s throughput
> After patch: around 72MB/s throughput
> 

Yes Yes that stupid Brain dead Server is no indication for anything. The server
should know best about optimal sizes and layouts. Please don't give me that stuff
again.

But just do the above and you'll see that it is perfect.

BTW don't limit the lo_segment size by the max_io_size. This is why you
have .bg_test to signal when IO is maxed out.

- The read segments should be as big as possible (i_size long)
- The Write segments should ideally be as big as the Application
  wants to write to. (Amount of dirty pages at time of nfs-write-out
  is a very good first approximation).

So I guess it is: I hate these patches, to much mess, too little goodness.

Thank
Boaz

> Peng Tao (4):
>   nfsv41: export pnfs_find_alloc_layout
>   nfsv41: add and export pnfs_find_get_layout_locked
>   nfsv41: get lseg before issue LD IO if pgio doesn't carry lseg
>   pnfsblock: do ask for layout in pg_init
> 
>  fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++-
>  fs/nfs/pnfs.c                    |   74 +++++++++++++++++++++++++++++++++++++-
>  fs/nfs/pnfs.h                    |    9 +++++
>  3 files changed, 134 insertions(+), 3 deletions(-)
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 01:34 PM, Boaz Harrosh wrote:
> But just do the above and you'll see that it is perfect.
> 
> BTW don't limit the lo_segment size by the max_io_size. This is why you
> have .bg_test to signal when IO is maxed out.
> 
> - The read segments should be as big as possible (i_size long)
> - The Write segments should ideally be as big as the Application
>   wants to write to. (Amount of dirty pages at time of nfs-write-out
>   is a very good first approximation).
> 
> So I guess it is: I hate these patches, to much mess, too little goodness.
> 
> Thank
> Boaz
> 

Ho and one more thing.

Also Files when they will support segments and servers that request segments,
like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
you know you want to write.

And surly Objects will enjoy that tremendously. Is it a 17 bytes text file, or
the beginning of a big video file.

But the problem with Files and Objects is that they need a layout first before
they can do the right thing in .pg_test and say if this belongs to this IO or
to the next. (Files is stipe_unit maxed+aliened, Objects raid-group boundary)

So your solution is not good for files and Objects, my way solves them two.

Thanks
Boaz

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 13:50 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 01:34 PM, Boaz Harrosh wrote:
> > But just do the above and you'll see that it is perfect.
> > 
> > BTW don't limit the lo_segment size by the max_io_size. This is why you
> > have .bg_test to signal when IO is maxed out.
> > 
> > - The read segments should be as big as possible (i_size long)
> > - The Write segments should ideally be as big as the Application
> >   wants to write to. (Amount of dirty pages at time of nfs-write-out
> >   is a very good first approximation).
> > 
> > So I guess it is: I hate these patches, to much mess, too little goodness.
> > 
> > Thank
> > Boaz
> > 
> 
> Ho and one more thing.
> 
> Also Files when they will support segments and servers that request segments,
> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
> you know you want to write.

Why would we want to add segment support to the pNFS files client???
Segments are a nuisance that multiply the amount of unnecessary chitchat
between the client and the MDS without providing any tangible
benefits...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 01:57 PM, Trond Myklebust wrote:
>> Also Files when they will support segments and servers that request segments,
>> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
>> you know you want to write.
> 
> Why would we want to add segment support to the pNFS files client???
> Segments are a nuisance that multiply the amount of unnecessary chitchat
> between the client and the MDS without providing any tangible
> benefits...
> 

Your kidding right?

One: it is mandated by the Standard, This is not an option. So a perfectly
     Standard complaint server is not Supported by Linux because we don't see
     the point.

Two: There are already file-layout servers out there (multiple) which are
     waiting for the Linux files-layout segment support, because the underline
     FS requires Segments and now they do not work with the Linux client. These
     are CEPH and GPFS and more.

The reason Netapp don't see a point is not a factor. I have not seen a netapp
server doing a top 100 HPC cluster either.

If the server hates the "unnecessary chitchat between the client and the MDS"
It can serve all-file layout and that is that. But some servers don't have
that privilege. Real big storage clusters with 1000thnds of DSs the data layout
might only be properly described by segments.

Let the fight begin. All the segmented file-layout servers out there. Now is
the time to take a stand.

Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> >> Also Files when they will support segments and servers that request segments,
> >> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
> >> you know you want to write.
> > 
> > Why would we want to add segment support to the pNFS files client???
> > Segments are a nuisance that multiply the amount of unnecessary chitchat
> > between the client and the MDS without providing any tangible
> > benefits...
> > 
> 
> Your kidding right?
> 
> One: it is mandated by the Standard, This is not an option. So a perfectly
>      Standard complaint server is not Supported by Linux because we don't see
>      the point.

Bollocks.. Nothing is "mandated by the Standard". If the server doesn't
give us a full layout, then we fall back to write through MDS. Why dick
around with crap that SLOWS YOU DOWN.

> Two: There are already file-layout servers out there (multiple) which are
>      waiting for the Linux files-layout segment support, because the underline
>      FS requires Segments and now they do not work with the Linux client. These
>      are CEPH and GPFS and more.

Then they will have a _long_ wait....

Trond

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 02:47 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
>> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
>>>> Also Files when they will support segments and servers that request segments,
>>>> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
>>>> you know you want to write.
>>>
>>> Why would we want to add segment support to the pNFS files client???
>>> Segments are a nuisance that multiply the amount of unnecessary chitchat
>>> between the client and the MDS without providing any tangible
>>> benefits...
>>>
>>
>> Your kidding right?
>>
>> One: it is mandated by the Standard, This is not an option. So a perfectly
>>      Standard complaint server is not Supported by Linux because we don't see
>>      the point.
> 
> Bollocks.. Nothing is "mandated by the Standard". If the server doesn't
> give us a full layout, then we fall back to write through MDS. Why dick
> around with crap that SLOWS YOU DOWN.
> 

NO! MAKE YOU FASTER.

The kind of typologies I'm talking about a single layout get ever 1GB is
marginal to the gain I get in deploying 100 of DSs. I have thousands of
DSs I want to spread the load evenly. I'm limited by the size of the layout
(Device info in the case of files) So I'm limited by the number of DSs I can
have in a layout. For large files these few devices become an hot spot all
the while the rest of the cluster is idle.

This is not a theory, we meet these problems ever day.

>> Two: There are already file-layout servers out there (multiple) which are
>>      waiting for the Linux files-layout segment support, because the underline
>>      FS requires Segments and now they do not work with the Linux client. These
>>      are CEPH and GPFS and more.
> 
> Then they will have a _long_ wait....
> 

OK, so now I understand. Because when I was talking to Fred before BAT and during
It was very very peculiar to me why he is not already done with that simple stuff.
Because usually Fred is such a brilliant fast programmer that I admire, and that simple
crap?

But now that explains

> Trond
> 

Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 02:47 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
> >> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> >>>> Also Files when they will support segments and servers that request segments,
> >>>> like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
> >>>> you know you want to write.
> >>>
> >>> Why would we want to add segment support to the pNFS files client???
> >>> Segments are a nuisance that multiply the amount of unnecessary chitchat
> >>> between the client and the MDS without providing any tangible
> >>> benefits...
> >>>
> >>
> >> Your kidding right?
> >>
> >> One: it is mandated by the Standard, This is not an option. So a perfectly
> >>      Standard complaint server is not Supported by Linux because we don't see
> >>      the point.
> > 
> > Bollocks.. Nothing is "mandated by the Standard". If the server doesn't
> > give us a full layout, then we fall back to write through MDS. Why dick
> > around with crap that SLOWS YOU DOWN.
> > 
> 
> NO! MAKE YOU FASTER.
> 
> The kind of typologies I'm talking about a single layout get ever 1GB is
> marginal to the gain I get in deploying 100 of DSs. I have thousands of
> DSs I want to spread the load evenly. I'm limited by the size of the layout
> (Device info in the case of files) So I'm limited by the number of DSs I can
> have in a layout. For large files these few devices become an hot spot all
> the while the rest of the cluster is idle.

I call "bullshit" on that whole argument...

You've done sod all so far to address the problem of a client managing
layout segments for a '1000 DS' case. Are you expecting that all pNFS
object servers out there are going to do that for you? How do I assume
that a generic pNFS files server is going to do the same? As far as I
know, the spec is completely moot on the whole subject.

IOW: I'm not even remotely interested in your "everyday problems" if
there are no "everyday solutions" that actually fit the generic can of
spec worms that the pNFS layout segments open.

> >> Two: There are already file-layout servers out there (multiple) which are
> >>      waiting for the Linux files-layout segment support, because the underline
> >>      FS requires Segments and now they do not work with the Linux client. These
> >>      are CEPH and GPFS and more.
> > 
> > Then they will have a _long_ wait....
> > 
> 
> OK, so now I understand. Because when I was talking to Fred before BAT and during
> It was very very peculiar to me why he is not already done with that simple stuff.
> Because usually Fred is such a brilliant fast programmer that I admire, and that simple
> crap?
> 
> But now that explains

Yes. It's all a big conspiracy, and we're deliberately holding Fred's
genius back in order to disappoint you...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Marc Eshel]

The only 1 cent that I can add to this argument is that I was led to 
believe by you and others that Linux kernel don't add functionality on the 
client side that is not supported on the server side. Last time I made 
this point I was told that it is ok if they are of by a version or two. 
You made it clear that this is no longer true and that the Linux client 
and server are now independent of each other. I spent time working on the 
server side believing that the client and server will progress more or 
less together, disappointed to find out that it is not the case any more.
Marc. 



From:
Trond Myklebust <Trond.Myklebust@netapp.com>
To:
Boaz Harrosh <bharrosh@panasas.com>
Cc:
Peng Tao <bergwolf@gmail.com>, linux-nfs@vger.kernel.org, 
bhalevy@tonian.com, Garth Gibson <garth@panasas.com>, Matt Benjamin 
<matt@linuxbox.com>, Marc Eshel <eshel@almaden.ibm.com>, Fred Isaman 
<iisaman@netapp.com>
Date:
11/29/2011 03:30 PM
Subject:
Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes



On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 02:47 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
> >> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> >>>> Also Files when they will support segments and servers that request 
segments,
> >>>> like the CEPH server, will very much enjoy the above, .i.e: Tell me 
the amount
> >>>> you know you want to write.
> >>>
> >>> Why would we want to add segment support to the pNFS files client???
> >>> Segments are a nuisance that multiply the amount of unnecessary 
chitchat
> >>> between the client and the MDS without providing any tangible
> >>> benefits...
> >>>
> >>
> >> Your kidding right?
> >>
> >> One: it is mandated by the Standard, This is not an option. So a 
perfectly
> >>      Standard complaint server is not Supported by Linux because we 
don't see
> >>      the point.
> > 
> > Bollocks.. Nothing is "mandated by the Standard". If the server 
doesn't
> > give us a full layout, then we fall back to write through MDS. Why 
dick
> > around with crap that SLOWS YOU DOWN.
> > 
> 
> NO! MAKE YOU FASTER.
> 
> The kind of typologies I'm talking about a single layout get ever 1GB is
> marginal to the gain I get in deploying 100 of DSs. I have thousands of
> DSs I want to spread the load evenly. I'm limited by the size of the 
layout
> (Device info in the case of files) So I'm limited by the number of DSs I 
can
> have in a layout. For large files these few devices become an hot spot 
all
> the while the rest of the cluster is idle.

I call "bullshit" on that whole argument...

You've done sod all so far to address the problem of a client managing
layout segments for a '1000 DS' case. Are you expecting that all pNFS
object servers out there are going to do that for you? How do I assume
that a generic pNFS files server is going to do the same? As far as I
know, the spec is completely moot on the whole subject.

IOW: I'm not even remotely interested in your "everyday problems" if
there are no "everyday solutions" that actually fit the generic can of
spec worms that the pNFS layout segments open.

> >> Two: There are already file-layout servers out there (multiple) which 
are
> >>      waiting for the Linux files-layout segment support, because the 
underline
> >>      FS requires Segments and now they do not work with the Linux 
client. These
> >>      are CEPH and GPFS and more.
> > 
> > Then they will have a _long_ wait....
> > 
> 
> OK, so now I understand. Because when I was talking to Fred before BAT 
and during
> It was very very peculiar to me why he is not already done with that 
simple stuff.
> Because usually Fred is such a brilliant fast programmer that I admire, 
and that simple
> crap?
> 
> But now that explains

Yes. It's all a big conspiracy, and we're deliberately holding Fred's
genius back in order to disappoint you...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 15:49 -0800, Marc Eshel wrote: 
> The only 1 cent that I can add to this argument is that I was led to 
> believe by you and others that Linux kernel don't add functionality on the 
> client side that is not supported on the server side. Last time I made 
> this point I was told that it is ok if they are of by a version or two. 
> You made it clear that this is no longer true and that the Linux client 
> and server are now independent of each other. I spent time working on the 
> server side believing that the client and server will progress more or 
> less together, disappointed to find out that it is not the case any more.
> Marc. 

I don't know how to manage layout segments in a way that meets the pNFS
goals of scalability and performance, and neither you nor the pNFS spec
have told me how to do this.

If IBM wants a client that implements layout segments, then it is _your_
responsibility to: 
     A. Convince me that it is an implementable part of the spec. 
     B. Provide me with an implementation that deals all with the
        concerns that I have.

IOW: nobody has ever promised IBM that the community would do all your
client work for you. EMC, NetApp and Panasas have implemented (most of)
the bits that they cared about; any bits that they haven't implemented
and that you care about are up to you.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Marc Eshel]

You ignored my main point, I was talking about the server side, my point 
was that there is nothing to build on on the serve side since the pNFS 
Linux server is not happening.
Marc.



From:
Trond Myklebust <Trond.Myklebust@netapp.com>
To:
Marc Eshel <eshel@almaden.ibm.com>
Cc:
Peng Tao <bergwolf@gmail.com>, bhalevy@tonian.com, Boaz Harrosh 
<bharrosh@panasas.com>, Garth Gibson <garth@panasas.com>, Fred Isaman 
<iisaman@netapp.com>, linux-nfs@vger.kernel.org, Matt Benjamin 
<matt@linuxbox.com>
Date:
11/29/2011 04:08 PM
Subject:
Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes



On Tue, 2011-11-29 at 15:49 -0800, Marc Eshel wrote: 
> The only 1 cent that I can add to this argument is that I was led to 
> believe by you and others that Linux kernel don't add functionality on 
the 
> client side that is not supported on the server side. Last time I made 
> this point I was told that it is ok if they are of by a version or two. 
> You made it clear that this is no longer true and that the Linux client 
> and server are now independent of each other. I spent time working on 
the 
> server side believing that the client and server will progress more or 
> less together, disappointed to find out that it is not the case any 
more.
> Marc. 

I don't know how to manage layout segments in a way that meets the pNFS
goals of scalability and performance, and neither you nor the pNFS spec
have told me how to do this.

If IBM wants a client that implements layout segments, then it is _your_
responsibility to: 
     A. Convince me that it is an implementable part of the spec. 
     B. Provide me with an implementation that deals all with the
        concerns that I have.

IOW: nobody has ever promised IBM that the community would do all your
client work for you. EMC, NetApp and Panasas have implemented (most of)
the bits that they cared about; any bits that they haven't implemented
and that you care about are up to you.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
> You ignored my main point, I was talking about the server side, my point 
> was that there is nothing to build on on the serve side since the pNFS 
> Linux server is not happening.
> Marc.

Sorry. I misunderstood your concern. As far as I know, the main problem
there is also one of investment: nobody has stepped up to help Bruce
write a pNFS server.

I'm less worried about this now than I was earlier, because other open
source efforts are gaining traction (see Ganesha - which is being
sponsored by IBM, and projects such as Tigran's java based pNFS server).
The other point is that we've developed client test-rigs that don't
depend on the availability of a Linux server (newpynfs and the pynfs
based proxy).

Cheers
  Trond 

> From:
> Trond Myklebust <Trond.Myklebust@netapp.com>
> To:
> Marc Eshel <eshel@almaden.ibm.com>
> Cc:
> Peng Tao <bergwolf@gmail.com>, bhalevy@tonian.com, Boaz Harrosh 
> <bharrosh@panasas.com>, Garth Gibson <garth@panasas.com>, Fred Isaman 
> <iisaman@netapp.com>, linux-nfs@vger.kernel.org, Matt Benjamin 
> <matt@linuxbox.com>
> Date:
> 11/29/2011 04:08 PM
> Subject:
> Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
> 
> 
> 
> On Tue, 2011-11-29 at 15:49 -0800, Marc Eshel wrote: 
> > The only 1 cent that I can add to this argument is that I was led to 
> > believe by you and others that Linux kernel don't add functionality on 
> the 
> > client side that is not supported on the server side. Last time I made 
> > this point I was told that it is ok if they are of by a version or two. 
> > You made it clear that this is no longer true and that the Linux client 
> > and server are now independent of each other. I spent time working on 
> the 
> > server side believing that the client and server will progress more or 
> > less together, disappointed to find out that it is not the case any 
> more.
> > Marc. 
> 
> I don't know how to manage layout segments in a way that meets the pNFS
> goals of scalability and performance, and neither you nor the pNFS spec
> have told me how to do this.
> 
> If IBM wants a client that implements layout segments, then it is _your_
> responsibility to: 
>      A. Convince me that it is an implementable part of the spec. 
>      B. Provide me with an implementation that deals all with the
>         concerns that I have.
> 
> IOW: nobody has ever promised IBM that the community would do all your
> client work for you. EMC, NetApp and Panasas have implemented (most of)
> the bits that they cared about; any bits that they haven't implemented
> and that you care about are up to you.
> 

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 04:37 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
>> You ignored my main point, I was talking about the server side, my point 
>> was that there is nothing to build on on the serve side since the pNFS 
>> Linux server is not happening.
>> Marc.
> 
> Sorry. I misunderstood your concern. As far as I know, the main problem
> there is also one of investment: nobody has stepped up to help Bruce
> write a pNFS server.
> 

I use "OUR" Linux pNFS Server every day, all day. It's there it is written
and it kicks us. We've been working on that for 5 Years now.

The only holding factor is that no one wants to do the final step and
fight the VFS guys to actually push it into Linus.

But it is there and alive in full open-source glory in Benny's tree.

> I'm less worried about this now than I was earlier, because other open
> source efforts are gaining traction (see Ganesha - which is being
> sponsored by IBM, and projects such as Tigran's java based pNFS server).
> The other point is that we've developed client test-rigs that don't
> depend on the availability of a Linux server (newpynfs and the pynfs
> based proxy).
> 

For me I'm testing with the linux Server and it is just there and works
well for me. Better than any other solution I have right now.

> Cheers
>   Trond 
> 

Ciao
Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[J. Bruce Fields]

On Tue, Nov 29, 2011 at 04:50:23PM -0800, Boaz Harrosh wrote:
> On 11/29/2011 04:37 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
> >> You ignored my main point, I was talking about the server side, my point 
> >> was that there is nothing to build on on the serve side since the pNFS 
> >> Linux server is not happening.
> >> Marc.
> > 
> > Sorry. I misunderstood your concern. As far as I know, the main problem
> > there is also one of investment: nobody has stepped up to help Bruce
> > write a pNFS server.
> > 
> 
> I use "OUR" Linux pNFS Server every day, all day. It's there it is written
> and it kicks us. We've been working on that for 5 Years now.
> 
> The only holding factor is that no one wants to do the final step and
> fight the VFS guys to actually push it into Linus.

As I've said before, my only requirement is that we hold off on merging
optional 4.1 features (like pNFS) until the *mandatory* parts of 4.1
comply with the spec.  Once that happens, I'm happy to help with merging
pNFS however I can, including working out any VFS problems.

Most of us have been assuming that the GFS2-backed server would be the
simplest to merge first, but with the client supporting all three layout
types, maybe it would be reasonable to start with the exofs-backed
server if that's in better shape.

To help the process along I'm continuing to maintain a 4.1 todo list:

	http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues#Highest_priority

I believe that could all be done relatively soon with some more help.

--b.


> But it is there and alive in full open-source glory in Benny's tree.
> 
> > I'm less worried about this now than I was earlier, because other open
> > source efforts are gaining traction (see Ganesha - which is being
> > sponsored by IBM, and projects such as Tigran's java based pNFS server).
> > The other point is that we've developed client test-rigs that don't
> > depend on the availability of a Linux server (newpynfs and the pynfs
> > based proxy).
> > 
> 
> For me I'm testing with the linux Server and it is just there and works
> well for me. Better than any other solution I have right now.
> 
> > Cheers
> >   Trond 
> > 
> 
> Ciao
> Heart
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Marc Eshel]

Trond Myklebust <Trond.Myklebust@netapp.com> wrote on 11/29/2011 04:37:05 
PM:
> 
> Peng Tao, bhalevy, Boaz Harrosh, Garth Gibson, Fred Isaman, linux-
> nfs, Matt Benjamin
> 
> On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
> > You ignored my main point, I was talking about the server side, my 
point 
> > was that there is nothing to build on on the serve side since the pNFS 

> > Linux server is not happening.
> > Marc.
> 
> Sorry. I misunderstood your concern. As far as I know, the main problem
> there is also one of investment: nobody has stepped up to help Bruce
> write a pNFS server.
> 
> I'm less worried about this now than I was earlier, because other open
> source efforts are gaining traction (see Ganesha - which is being
> sponsored by IBM, and projects such as Tigran's java based pNFS server).
> The other point is that we've developed client test-rigs that don't
> depend on the availability of a Linux server (newpynfs and the pynfs
> based proxy).

You got it backward, Ganesha is getting traction precisely because the 
Linux kernel server is not happening :)
Sorry, I did not mean to change the topic of this thread, go back to 
addressing Boaz's concern.
Marc. 

> 
> Cheers
>   Trond 
> 
> > From:
> > Trond Myklebust <Trond.Myklebust@netapp.com>
> > To:
> > Marc Eshel <eshel@almaden.ibm.com>
> > Cc:
> > Peng Tao <bergwolf@gmail.com>, bhalevy@tonian.com, Boaz Harrosh 
> > <bharrosh@panasas.com>, Garth Gibson <garth@panasas.com>, Fred Isaman 
> > <iisaman@netapp.com>, linux-nfs@vger.kernel.org, Matt Benjamin 
> > <matt@linuxbox.com>
> > Date:
> > 11/29/2011 04:08 PM
> > Subject:
> > Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
> > 
> > 
> > 
> > On Tue, 2011-11-29 at 15:49 -0800, Marc Eshel wrote: 
> > > The only 1 cent that I can add to this argument is that I was led to 

> > > believe by you and others that Linux kernel don't add functionality 
on 
> > the 
> > > client side that is not supported on the server side. Last time I 
made 
> > > this point I was told that it is ok if they are of by a version or 
two. 
> > > You made it clear that this is no longer true and that the Linux 
client 
> > > and server are now independent of each other. I spent time working 
on 
> > the 
> > > server side believing that the client and server will progress more 
or 
> > > less together, disappointed to find out that it is not the case any 
> > more.
> > > Marc. 
> > 
> > I don't know how to manage layout segments in a way that meets the 
pNFS
> > goals of scalability and performance, and neither you nor the pNFS 
spec
> > have told me how to do this.
> > 
> > If IBM wants a client that implements layout segments, then it is 
_your_
> > responsibility to: 
> >      A. Convince me that it is an implementable part of the spec. 
> >      B. Provide me with an implementation that deals all with the
> >         concerns that I have.
> > 
> > IOW: nobody has ever promised IBM that the community would do all your
> > client work for you. EMC, NetApp and Panasas have implemented (most 
of)
> > the bits that they cared about; any bits that they haven't implemented
> > and that you care about are up to you.
> > 
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com
> 

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[J. Bruce Fields]

On Tue, Nov 29, 2011 at 04:52:59PM -0800, Marc Eshel wrote:
> Trond Myklebust <Trond.Myklebust@netapp.com> wrote on 11/29/2011 04:37:05 
> PM:
> > 
> > Peng Tao, bhalevy, Boaz Harrosh, Garth Gibson, Fred Isaman, linux-
> > nfs, Matt Benjamin
> > 
> > On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
> > > You ignored my main point, I was talking about the server side, my 
> point 
> > > was that there is nothing to build on on the serve side since the pNFS 
> 
> > > Linux server is not happening.
> > > Marc.
> > 
> > Sorry. I misunderstood your concern. As far as I know, the main problem
> > there is also one of investment: nobody has stepped up to help Bruce
> > write a pNFS server.
> > 
> > I'm less worried about this now than I was earlier, because other open
> > source efforts are gaining traction (see Ganesha - which is being
> > sponsored by IBM, and projects such as Tigran's java based pNFS server).
> > The other point is that we've developed client test-rigs that don't
> > depend on the availability of a Linux server (newpynfs and the pynfs
> > based proxy).
> 
> You got it backward, Ganesha is getting traction precisely because the 
> Linux kernel server is not happening :)

My understanding is the same as Trond's--the reason it's not happening
is because nobody is making an effort to merge it.  What am I missing?

--b.

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Benny Halevy]

On 2011-11-30 21:44, J. Bruce Fields wrote:
> On Tue, Nov 29, 2011 at 04:52:59PM -0800, Marc Eshel wrote:
>> Trond Myklebust <Trond.Myklebust@netapp.com> wrote on 11/29/2011 04:37:05 
>> PM:
>>>
>>> Peng Tao, bhalevy, Boaz Harrosh, Garth Gibson, Fred Isaman, linux-
>>> nfs, Matt Benjamin
>>>
>>> On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
>>>> You ignored my main point, I was talking about the server side, my 
>> point 
>>>> was that there is nothing to build on on the serve side since the pNFS 
>>
>>>> Linux server is not happening.
>>>> Marc.
>>>
>>> Sorry. I misunderstood your concern. As far as I know, the main problem
>>> there is also one of investment: nobody has stepped up to help Bruce
>>> write a pNFS server.
>>>
>>> I'm less worried about this now than I was earlier, because other open
>>> source efforts are gaining traction (see Ganesha - which is being
>>> sponsored by IBM, and projects such as Tigran's java based pNFS server).
>>> The other point is that we've developed client test-rigs that don't
>>> depend on the availability of a Linux server (newpynfs and the pynfs
>>> based proxy).
>>
>> You got it backward, Ganesha is getting traction precisely because the 
>> Linux kernel server is not happening :)
> 
> My understanding is the same as Trond's--the reason it's not happening
> is because nobody is making an effort to merge it.  What am I missing?
> 

Tonian is working on this and we've allocated resources also to help
out on your nfs4.1 todo list.

Benny

> --b.

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[J. Bruce Fields]

On Thu, Dec 01, 2011 at 11:47:05AM +0200, Benny Halevy wrote:
> On 2011-11-30 21:44, J. Bruce Fields wrote:
> > On Tue, Nov 29, 2011 at 04:52:59PM -0800, Marc Eshel wrote:
> >> Trond Myklebust <Trond.Myklebust@netapp.com> wrote on 11/29/2011 04:37:05 
> >> PM:
> >>>
> >>> Peng Tao, bhalevy, Boaz Harrosh, Garth Gibson, Fred Isaman, linux-
> >>> nfs, Matt Benjamin
> >>>
> >>> On Tue, 2011-11-29 at 16:20 -0800, Marc Eshel wrote: 
> >>>> You ignored my main point, I was talking about the server side, my 
> >> point 
> >>>> was that there is nothing to build on on the serve side since the pNFS 
> >>
> >>>> Linux server is not happening.
> >>>> Marc.
> >>>
> >>> Sorry. I misunderstood your concern. As far as I know, the main problem
> >>> there is also one of investment: nobody has stepped up to help Bruce
> >>> write a pNFS server.
> >>>
> >>> I'm less worried about this now than I was earlier, because other open
> >>> source efforts are gaining traction (see Ganesha - which is being
> >>> sponsored by IBM, and projects such as Tigran's java based pNFS server).
> >>> The other point is that we've developed client test-rigs that don't
> >>> depend on the availability of a Linux server (newpynfs and the pynfs
> >>> based proxy).
> >>
> >> You got it backward, Ganesha is getting traction precisely because the 
> >> Linux kernel server is not happening :)
> > 
> > My understanding is the same as Trond's--the reason it's not happening
> > is because nobody is making an effort to merge it.  What am I missing?
> > 
> 
> Tonian is working on this and we've allocated resources also to help
> out on your nfs4.1 todo list.

Great, thanks; let me know how I can help.

--b.

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[J. Bruce Fields]

On Thu, Dec 01, 2011 at 06:14:57AM -0500, J. Bruce Fields wrote:
> On Thu, Dec 01, 2011 at 11:47:05AM +0200, Benny Halevy wrote:
> > On 2011-11-30 21:44, J. Bruce Fields wrote:
> > > My understanding is the same as Trond's--the reason it's not happening
> > > is because nobody is making an effort to merge it.  What am I missing?
> > > 
> > 
> > Tonian is working on this and we've allocated resources also to help
> > out on your nfs4.1 todo list.
> 
> Great, thanks; let me know how I can help.

(And, apologies, I shouldn't have said *nobody*: Mi Jinlong has been
doing some good work for a while now.  I also appreciate that you've
managed to squeeze in some time for testing and the occasional patch.
And thanks to Lior for the help triaging pynfs issues--I do hope to get
back to that soon.  But this code still isn't getting the love it
needs....)

--b.

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 04:08 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 15:49 -0800, Marc Eshel wrote: 
>> The only 1 cent that I can add to this argument is that I was led to 
>> believe by you and others that Linux kernel don't add functionality on the 
>> client side that is not supported on the server side. Last time I made 
>> this point I was told that it is ok if they are of by a version or two. 
>> You made it clear that this is no longer true and that the Linux client 
>> and server are now independent of each other. I spent time working on the 
>> server side believing that the client and server will progress more or 
>> less together, disappointed to find out that it is not the case any more.
>> Marc. 
> 
> I don't know how to manage layout segments in a way that meets the pNFS
> goals of scalability and performance, and neither you nor the pNFS spec
> have told me how to do this.

This I do not understand. What is the problem with current implementation?
I use these segments every day and see performance through the roof. I'm
able to saturate any cluster I throw at it and am happy as bliss. And it's
surprisingly stable. My IO flow is full of segments and recalls, and it
works surprisingly well.

(I intend to send some hard numbers next week. But believe me they are
 amassing)

> 
> If IBM wants a client that implements layout segments, then it is _your_
> responsibility to: 
>      A. Convince me that it is an implementable part of the spec. 

Sure

>      B. Provide me with an implementation that deals all with the
>         concerns that I have.
> 

What concerns are that. If it's the COMMITs then I think I know what
todo.

> IOW: nobody has ever promised IBM that the community would do all your
> client work for you. EMC, NetApp and Panasas have implemented (most of)
> the bits that they cared about; any bits that they haven't implemented
> and that you care about are up to you.
> 

I think I'll pick this up. Me or some interested people I know. Until now
it was said that Fred is working on that and we waited patiently for him
to do it out of respect and to save any wasted efforts. But if it's dropped
on the floor, then I'm all the gladder to pick it up. Just give me the green
light because I do not want to duplicate efforts.

Thanks
Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 03:30 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
>>
>> The kind of typologies I'm talking about a single layout get ever 1GB is
>> marginal to the gain I get in deploying 100 of DSs. I have thousands of
>> DSs I want to spread the load evenly. I'm limited by the size of the layout
>> (Device info in the case of files) So I'm limited by the number of DSs I can
>> have in a layout. For large files these few devices become an hot spot all
>> the while the rest of the cluster is idle.
> 
> I call "bullshit" on that whole argument...
> 
> You've done sod all so far to address the problem of a client managing

sod? I don't know this word?

> layout segments for a '1000 DS' case. Are you expecting that all pNFS
> object servers out there are going to do that for you? How do I assume
> that a generic pNFS files server is going to do the same? As far as I
> know, the spec is completely moot on the whole subject.
> 

What? The all segments thing is in the Generic part of the spec and is not
at all specific or even specified in the objects and blocks RFCs.

There is no layout in the spec, there are only layout_segments. Actually
what we call layout_segments, in the spec, it is simply called a layout.

The client asks for a layout (segment) and gets one. An ~0 length one
is just a special case. Without layout_get (segment) there is no optional
pnfs support.

So we are reading two different specs because to me it clearly says
layout - which is a segment.

Because the way I read it the pNFS is optional in 4.1. But if I'm a
pNFS client I need to expect layouts (segments)

> IOW: I'm not even remotely interested in your "everyday problems" if
> there are no "everyday solutions" that actually fit the generic can of
> spec worms that the pNFS layout segments open.

That I don't understand. What "spec worms that the pNFS layout segments open"
Are you seeing. Because it works pretty simple for me. And I don't see the
big difference for files. One thing I learned for the past is that when you
have concerns I should understand them and start to address them. Because
your insights are usually on the Money. If you are concerned then there is
something I should fix.

Fred told me about his COMMIT problem. And in my opinion he is doing it
the wrong way.

He is trying to consolidate commits across lo_segments. But to the contrary
he should keep it as is and bound the commit to segments boundary.
If a server is giving out all-file then above problem is mute.

but if the Server gave out segments. Then for him he anticipates all operations
segmented. Usually the servers I saw will always have different DSs on these other
segments and the hard work will not matter at all. If not then Such a server will
anticipate that the COMMITS will be finer then what could theoretically be done.
And could take that into account. In anyway that's what they'll get.

So please don't solve for the theoretical case that no one uses. (Same DSs repeat
in the next segments)

> 
>>>> Two: There are already file-layout servers out there (multiple) which are
>>>>      waiting for the Linux files-layout segment support, because the underline
>>>>      FS requires Segments and now they do not work with the Linux client. These
>>>>      are CEPH and GPFS and more.
>>>
>>> Then they will have a _long_ wait....
>>>
>>
>> OK, so now I understand. Because when I was talking to Fred before BAT and during
>> It was very very peculiar to me why he is not already done with that simple stuff.
>> Because usually Fred is such a brilliant fast programmer that I admire, and that simple
>> crap?
>>
>> But now that explains
> 
> Yes. It's all a big conspiracy, and we're deliberately holding Fred's
> genius back in order to disappoint you...
> 

My disappointment is that I think it is important for me that the pNFS protocol can
take a strong-hold in the HPC and cloud market (and everywhere). And for that to happen
all layout types including files must excel and shine. I'm constantly trying to architect
an HPC cluster class parallel Filesystem with Files-layout as well. But keeps getting hits
from small trivialities that make the all difference. (Another example is that EOF talk
we had the other day)

I'm a patience guy I can wait until you guys see the light.

Thanks
Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 16:24 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 03:30 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
> >>
> >> The kind of typologies I'm talking about a single layout get ever 1GB is
> >> marginal to the gain I get in deploying 100 of DSs. I have thousands of
> >> DSs I want to spread the load evenly. I'm limited by the size of the layout
> >> (Device info in the case of files) So I'm limited by the number of DSs I can
> >> have in a layout. For large files these few devices become an hot spot all
> >> the while the rest of the cluster is idle.
> > 
> > I call "bullshit" on that whole argument...
> > 
> > You've done sod all so far to address the problem of a client managing
> 
> sod? I don't know this word?

'sod all' == 'nothing'

it's an English slang...

> > layout segments for a '1000 DS' case. Are you expecting that all pNFS
> > object servers out there are going to do that for you? How do I assume
> > that a generic pNFS files server is going to do the same? As far as I
> > know, the spec is completely moot on the whole subject.
> > 
> 
> What? The all segments thing is in the Generic part of the spec and is not
> at all specific or even specified in the objects and blocks RFCs.

..and it doesn't say _anything_ about how a client is supposed to manage
them in order to maximise efficiency.

> There is no layout in the spec, there are only layout_segments. Actually
> what we call layout_segments, in the spec, it is simply called a layout.
> 
> The client asks for a layout (segment) and gets one. An ~0 length one
> is just a special case. Without layout_get (segment) there is no optional
> pnfs support.
> 
> So we are reading two different specs because to me it clearly says
> layout - which is a segment.
> 
> Because the way I read it the pNFS is optional in 4.1. But if I'm a
> pNFS client I need to expect layouts (segments)
> 
> > IOW: I'm not even remotely interested in your "everyday problems" if
> > there are no "everyday solutions" that actually fit the generic can of
> > spec worms that the pNFS layout segments open.
> 
> That I don't understand. What "spec worms that the pNFS layout segments open"
> Are you seeing. Because it works pretty simple for me. And I don't see the
> big difference for files. One thing I learned for the past is that when you
> have concerns I should understand them and start to address them. Because
> your insights are usually on the Money. If you are concerned then there is
> something I should fix.

I'm saying that if I need to manage layouts that deal with >1000 DSes,
then I presumably need a strategy for ensuring that I return/forget
segments that are no longer needed, and I need a strategy for ensuring
that I always hold the segments that I do need; otherwise, I could just
ask for a full-file layout and deal with the 1000 DSes (which is what we
do today)...

My problem is that the spec certainly doesn't give me any guidance as to
such a strategy, and I haven't seen anybody else step up to the plate.
In fact, I strongly suspect that such a strategy is going to be very
application specific.

IOW: I don't accept that a layout-segment based solution is useful
without some form of strategy for telling me which segments to keep and
which to throw out when I start hitting client resource limits. I also
haven't seen any strategy out there for setting loga_length (as opposed
to loga_minlength) in the LAYOUTGET requests: as far as I know that is
going to be heavily application-dependent in the 1000-DS world.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 04:58 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 16:24 -0800, Boaz Harrosh wrote: 
>> On 11/29/2011 03:30 PM, Trond Myklebust wrote:
>>> On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
>>
>> That I don't understand. What "spec worms that the pNFS layout segments open"
>> Are you seeing. Because it works pretty simple for me. And I don't see the
>> big difference for files. One thing I learned for the past is that when you
>> have concerns I should understand them and start to address them. Because
>> your insights are usually on the Money. If you are concerned then there is
>> something I should fix.
> 
> I'm saying that if I need to manage layouts that deal with >1000 DSes,
> then I presumably need a strategy for ensuring that I return/forget
> segments that are no longer needed, and I need a strategy for ensuring
> that I always hold the segments that I do need; otherwise, I could just
> ask for a full-file layout and deal with the 1000 DSes (which is what we
> do today)...
> 

Thanks for asking because now I can answer you and you will find that I'm
one step a head in some of the issues.

1. The 1000 DSes problem is separate from the segments problem. The devices
   solution is on the way. The device cache is all but ready to see some
   periodic scan that throws 0 used devices. We never got to it because
   currently every one is testing with up to 10 devices and I'm using upto
   128 devices which is just fine. The load is marginal so far.
   But I promise you it is right here on my to do list. After some more
   pressed problem.
   Lets say one thing this subsystem is the same regardless of if the
   1000 devices are refed by 1 segment or by 10 segments. Actually if
   by 10 then I might get rid of some and free devices.

2. The many segments problem. There are not that many. It's more less
   a segment for every 2GB so an lo_seg struct for so much IO is not
   noticeable.
   At the upper bound we do not have any problem because Once the system is
   out of memory it will start to evict inodes. And on evict we just return
   them. Also ROC Servers we forget them on close. So so far all our combined
   testing did not show any real memory pressure caused by that. When shown we
   can start discarding segs in an LRU fashion. There are all the mechanics
   to do that, we only need to see the need.

3. The current situation is fine and working and showing great performance
   for objects and blocks. And it is all in the Generic part so it should just
   be the same for files. I do not see any difference.

   The only BUG I see is the COMMIT and I think we know how to fix that

> My problem is that the spec certainly doesn't give me any guidance as to
> such a strategy, and I haven't seen anybody else step up to the plate.
> In fact, I strongly suspect that such a strategy is going to be very
> application specific.
> 

You never asked. I'm thinking about these things all the time. Currently
we are far behind the limits of a running system. I think I'm going to
get to these limits before any one else.

My strategy is stated above LRU for devices is almost all there ref-counting
and all only the periodic timer needs to be added.
LRU for segments is more work, but is doable. But the segments count are
so low that we will not hit that problem for a long time. Before I ship
a system that will break that barrier I'll send a fix I promise.

> IOW: I don't accept that a layout-segment based solution is useful
> without some form of strategy for telling me which segments to keep and
> which to throw out when I start hitting client resource limits. 

LRU. Again there are not more than a few segments per inode. It's not
1000 like devices.

> I also
> haven't seen any strategy out there for setting loga_length (as opposed
> to loga_minlength) in the LAYOUTGET requests: as far as I know that is
> going to be heavily application-dependent in the 1000-DS world.
> 

Current situation is working for me. But we also are actively working to
improve it. What we want is that files-LO can enjoy the same privileges that
objects and blocks already have, in exactly the same, simple stupid but working,
way.

All your above concerns are true and interesting. I call them a rich man problems.
But they are not specific to files-LO they are generic to all of us. Current situation
satisfies us for blocks and objects. The file guys out there are jealous.

Thanks
Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 17:46 -0800, Boaz Harrosh wrote: 
> On 11/29/2011 04:58 PM, Trond Myklebust wrote:
> > On Tue, 2011-11-29 at 16:24 -0800, Boaz Harrosh wrote: 
> >> On 11/29/2011 03:30 PM, Trond Myklebust wrote:
> >>> On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
> >>
> >> That I don't understand. What "spec worms that the pNFS layout segments open"
> >> Are you seeing. Because it works pretty simple for me. And I don't see the
> >> big difference for files. One thing I learned for the past is that when you
> >> have concerns I should understand them and start to address them. Because
> >> your insights are usually on the Money. If you are concerned then there is
> >> something I should fix.
> > 
> > I'm saying that if I need to manage layouts that deal with >1000 DSes,
> > then I presumably need a strategy for ensuring that I return/forget
> > segments that are no longer needed, and I need a strategy for ensuring
> > that I always hold the segments that I do need; otherwise, I could just
> > ask for a full-file layout and deal with the 1000 DSes (which is what we
> > do today)...
> > 
> 
> Thanks for asking because now I can answer you and you will find that I'm
> one step a head in some of the issues.
> 
> 1. The 1000 DSes problem is separate from the segments problem. The devices

Errr... That was the problem that you used to justify the need for a
full implementation of layout segments in the pNFS files case...

> solution is on the way. The device cache is all but ready to see some
>    periodic scan that throws 0 used devices. We never got to it because
>    currently every one is testing with up to 10 devices and I'm using upto
>    128 devices which is just fine. The load is marginal so far.
>    But I promise you it is right here on my to do list. After some more
>    pressed problem.
>    Lets say one thing this subsystem is the same regardless of if the
>    1000 devices are refed by 1 segment or by 10 segments. Actually if
>    by 10 then I might get rid of some and free devices.
> 
> 2. The many segments problem. There are not that many. It's more less
>    a segment for every 2GB so an lo_seg struct for so much IO is not
>    noticeable.

Where do you get that 2GB number from?

> At the upper bound we do not have any problem because Once the system is
>    out of memory it will start to evict inodes. And on evict we just return
>    them. Also ROC Servers we forget them on close. So so far all our combined
>    testing did not show any real memory pressure caused by that. When shown we
>    can start discarding segs in an LRU fashion. There are all the mechanics
>    to do that, we only need to see the need.

It's not necessarily that simple: if you are already low on memory, them
LAYOUTGET and GETDEVICE will require you to allocate more memory in
order to get round to cleaning those dirty pages.
There are plenty of situations where the majority of dirty pages belong
to a single file. If that file is one of your 1000 DS-files and it
requires you to allocate 1000 new device table entries...

> 3. The current situation is fine and working and showing great performance
>    for objects and blocks. And it is all in the Generic part so it should just
>    be the same for files. I do not see any difference.
> 
>    The only BUG I see is the COMMIT and I think we know how to fix that

I haven't seen any performance numbers for either, so I can't comment.

> > My problem is that the spec certainly doesn't give me any guidance as to
> > such a strategy, and I haven't seen anybody else step up to the plate.
> > In fact, I strongly suspect that such a strategy is going to be very
> > application specific.
> > 
> 
> You never asked. I'm thinking about these things all the time. Currently
> we are far behind the limits of a running system. I think I'm going to
> get to these limits before any one else.
> 
> My strategy is stated above LRU for devices is almost all there ref-counting
> and all only the periodic timer needs to be added.
> LRU for segments is more work, but is doable. But the segments count are
> so low that we will not hit that problem for a long time. Before I ship
> a system that will break that barrier I'll send a fix I promise.

As far as pNFS files is concerned, the memory pressure should be driven
by the number of devices (i.e. DSes).

> > IOW: I don't accept that a layout-segment based solution is useful
> > without some form of strategy for telling me which segments to keep and
> > which to throw out when I start hitting client resource limits. 
> 
> LRU. Again there are not more than a few segments per inode. It's not
> 1000 like devices.

Again, the problem for files shouldn't be the number of segments, it is
number of devices.

> > I also
> > haven't seen any strategy out there for setting loga_length (as opposed
> > to loga_minlength) in the LAYOUTGET requests: as far as I know that is
> > going to be heavily application-dependent in the 1000-DS world.
> > 
> 
> Current situation is working for me. But we also are actively working to
> improve it. What we want is that files-LO can enjoy the same privileges that
> objects and blocks already have, in exactly the same, simple stupid but working,
> way.
> 
> All your above concerns are true and interesting. I call them a rich man problems.
> But they are not specific to files-LO they are generic to all of us. Current situation
> satisfies us for blocks and objects. The file guys out there are jealous.

I'm not convinced that the problems are the same. objects, and
particularly blocks, appear to treat layout segments as a form of byte
range lock. There is no reason for a pNFS files server to do so.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 06:07 PM, Trond Myklebust wrote:
>>
>> 1. The 1000 DSes problem is separate from the segments problem. The devices
> 
> Errr... That was the problem that you used to justify the need for a
> full implementation of layout segments in the pNFS files case...
> 

What I do not understand? I said what?

>> solution is on the way. The device cache is all but ready to see some
>>    periodic scan that throws 0 used devices. We never got to it because
>>    currently every one is testing with up to 10 devices and I'm using upto
>>    128 devices which is just fine. The load is marginal so far.
>>    But I promise you it is right here on my to do list. After some more
>>    pressed problem.
>>    Lets say one thing this subsystem is the same regardless of if the
>>    1000 devices are refed by 1 segment or by 10 segments. Actually if
>>    by 10 then I might get rid of some and free devices.
>>
>> 2. The many segments problem. There are not that many. It's more less
>>    a segment for every 2GB so an lo_seg struct for so much IO is not
>>    noticeable.
> 
> Where do you get that 2GB number from?
> 

It's just the numbers that I saw and used. I'm just giving you an example
usage. The numbers guys are looking for are not seg for every 4K but seg
every Giga. That's what I'm saying. When you asses the problem you should
attack the expected and current behavior.

When a smart ass Server comes and serves 4k segments and all it's Clients go
OOM, how long that Server will stay in business? I don't care about him
I care about a properly set balance and that is what we arrived at both in
Panasas and else where.

>> At the upper bound we do not have any problem because Once the system is
>>    out of memory it will start to evict inodes. And on evict we just return
>>    them. Also ROC Servers we forget them on close. So so far all our combined
>>    testing did not show any real memory pressure caused by that. When shown we
>>    can start discarding segs in an LRU fashion. There are all the mechanics
>>    to do that, we only need to see the need.
> 
> It's not necessarily that simple: if you are already low on memory, them
> LAYOUTGET and GETDEVICE will require you to allocate more memory in
> order to get round to cleaning those dirty pages.
> There are plenty of situations where the majority of dirty pages belong
> to a single file. If that file is one of your 1000 DS-files and it
> requires you to allocate 1000 new device table entries...
> 

No!!! That is the all-file layout problem. In a balanced and segmented
system. You don't. You start by getting a small number of devices corresponding
to the first seg. send the IO, when the IO returns, given memory pressure
you can free the segment, and it's ref-ed devices and continue with the next
seg. You can do this all day visiting all the 1000 devices with never having
more then 10 at a time.

The ratios are fine. For every 1GB of dirty pages I have one layout and 10
devices. It's marginal and expected memory needs for IO. Should I start with
the block layer scsi layer iscsi LLD networking stack, they all need more
memory to clear memory. If the system makes sure that dirty pages pressure
starts soon enough the system should be fine.

>> 3. The current situation is fine and working and showing great performance
>>    for objects and blocks. And it is all in the Generic part so it should just
>>    be the same for files. I do not see any difference.
>>
>>    The only BUG I see is the COMMIT and I think we know how to fix that
> 
> I haven't seen any performance numbers for either, so I can't comment.
> 

890MB single 10G client single stream.
3.6G 16 clients N x N from a 4.0G theoretical storage limit.

Please Believe me nice numbers. It is all very balanced. 2G segments
10 devices each segment. Smooth as silk

>>
>> LRU. Again there are not more than a few segments per inode. It's not
>> 1000 like devices.
> 
> Again, the problem for files shouldn't be the number of segments, it is
> number of devices.
> 

Right! And the all-file layout makes it worse. With segments the DSs can
be de-refed early making room for new devices. It is all a matter of keeping
your numbers balanced. When you get it wrong your client performance drops.

All we (the client need to care) is that we don't crash and do the right
thing. If a server returns a 1000 DSs segment then we return E-RESOURCE.
Hell the xdr buffer for get device info will be much to small long before
that. But is the server returns 10 devices at a time that can be discarded
before the next segment then we are fine, right?

>>
>> All your above concerns are true and interesting. I call them a rich man problems.
>> But they are not specific to files-LO they are generic to all of us. Current situation
>> satisfies us for blocks and objects. The file guys out there are jealous.
> 
> I'm not convinced that the problems are the same. objects, and
> particularly blocks, appear to treat layout segments as a form of byte
> range lock. There is no reason for a pNFS files server to do so.
> 

Trond this is not fair. You are back to your old self again. A files layout
guy just told you that it's cluster's data layout cannot be described in a
single deviceinfo+layout and his topology requires segmented topology. Locks or
no locks. that's beside the issue.

In objects only for RAID5 it is true what you say because you cannot have
two clients writing the same stripe. But for RAID0 there is no such restriction.
For a long time I served all-file until I had a system with more than 21 objects
the 21 objects is the limit of the layout_get buffer from client. So now I serve
10 device segments at a time, which gives me a nice balance. And actually works
much better than the old all-file way. It is liter Both on the Server implementation
and on the Client.

You are dodging our problem. There are true servers out there that have typologies
that needs segments in exactly the type of numbers that I'm talking about. The
current implementation is just fine. All they want is the restriction lifted and
the COMMIT bug fixed. They do not ask for anything else, more.

And soon enough I will demonstrate to you a (virtual) 1000 devices file working
just fine. Once I get that devices-cache LRU in place.

Lets say that the RAID0 objects behavior is identical to the files-LO which is
RAID0 only. (No recalls on stripe conflicts) so if it works very nice for
objects I don't see why it should have problems for files?

If I send you a patch that fixes the COMMIT problem in files layout
will you consider it?

Heart

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Benny Halevy]

On 2011-11-30 02:58, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 16:24 -0800, Boaz Harrosh wrote: 
>> On 11/29/2011 03:30 PM, Trond Myklebust wrote:
>>> On Tue, 2011-11-29 at 14:58 -0800, Boaz Harrosh wrote: 
>>>>
>>>> The kind of typologies I'm talking about a single layout get ever 1GB is
>>>> marginal to the gain I get in deploying 100 of DSs. I have thousands of
>>>> DSs I want to spread the load evenly. I'm limited by the size of the layout
>>>> (Device info in the case of files) So I'm limited by the number of DSs I can
>>>> have in a layout. For large files these few devices become an hot spot all
>>>> the while the rest of the cluster is idle.
>>>
>>> I call "bullshit" on that whole argument...
>>>
>>> You've done sod all so far to address the problem of a client managing
>>
>> sod? I don't know this word?
> 
> 'sod all' == 'nothing'
> 
> it's an English slang...
> 
>>> layout segments for a '1000 DS' case. Are you expecting that all pNFS
>>> object servers out there are going to do that for you? How do I assume
>>> that a generic pNFS files server is going to do the same? As far as I
>>> know, the spec is completely moot on the whole subject.
>>>
>>
>> What? The all segments thing is in the Generic part of the spec and is not
>> at all specific or even specified in the objects and blocks RFCs.
> 
> ..and it doesn't say _anything_ about how a client is supposed to manage
> them in order to maximise efficiency.
> 
>> There is no layout in the spec, there are only layout_segments. Actually
>> what we call layout_segments, in the spec, it is simply called a layout.
>>
>> The client asks for a layout (segment) and gets one. An ~0 length one
>> is just a special case. Without layout_get (segment) there is no optional
>> pnfs support.
>>
>> So we are reading two different specs because to me it clearly says
>> layout - which is a segment.
>>
>> Because the way I read it the pNFS is optional in 4.1. But if I'm a
>> pNFS client I need to expect layouts (segments)
>>
>>> IOW: I'm not even remotely interested in your "everyday problems" if
>>> there are no "everyday solutions" that actually fit the generic can of
>>> spec worms that the pNFS layout segments open.
>>
>> That I don't understand. What "spec worms that the pNFS layout segments open"
>> Are you seeing. Because it works pretty simple for me. And I don't see the
>> big difference for files. One thing I learned for the past is that when you
>> have concerns I should understand them and start to address them. Because
>> your insights are usually on the Money. If you are concerned then there is
>> something I should fix.
> 
> I'm saying that if I need to manage layouts that deal with >1000 DSes,
> then I presumably need a strategy for ensuring that I return/forget
> segments that are no longer needed, and I need a strategy for ensuring
> that I always hold the segments that I do need; otherwise, I could just
> ask for a full-file layout and deal with the 1000 DSes (which is what we
> do today)...111

How about LRU based caching to start with?

> 
> My problem is that the spec certainly doesn't give me any guidance as to
> such a strategy, and I haven't seen anybody else step up to the plate.
> In fact, I strongly suspect that such a strategy is going to be very
> application specific.


The spec doesn't give much guidance to the client as per data caching
replacement algorithms either and still we cache data in the client and
do our best to accommodate the application needs.

> 
> IOW: I don't accept that a layout-segment based solution is useful
> without some form of strategy for telling me which segments to keep and
> which to throw out when I start hitting client resource limits. I also
> haven't seen any strategy out there for setting loga_length (as opposed
> to loga_minlength) in the LAYOUTGET requests: as far as I know that is
> going to be heavily application-dependent in the 1000-DS world.
> 

My approach has always been: the client should ask for what it knows about
and the server may optimize over it.  If the client can anticipate the
application behavior, a-la sequential read-ahead it can attempt to
use that, but the server has better knowledge of the entire cluster workload
to determine the appropriate layout segment range.

Benny

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Matt W. Benjamin]

That would be pretty disappointing.  However, based on previous interactions, my belief would be, the
Linux client will do what can be shown empirically to work better, or more correctly.

Matt

----- "Trond Myklebust" <Trond.Myklebust@netapp.com> wrote:

> On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
> > On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> > >> Also Files when they will support segments and servers that
> request segments,
> > >> like the CEPH server, will very much enjoy the above, .i.e: Tell
> me the amount
> > >> you know you want to write.
> > > 
> > > Why would we want to add segment support to the pNFS files
> client???
> > > Segments are a nuisance that multiply the amount of unnecessary
> chitchat
> > > between the client and the MDS without providing any tangible
> > > benefits...
> > > 
> > 
> > Your kidding right?
> > 
> > One: it is mandated by the Standard, This is not an option. So a
> perfectly
> >      Standard complaint server is not Supported by Linux because we
> don't see
> >      the point.
> 
> Bollocks.. Nothing is "mandated by the Standard". If the server
> doesn't
> give us a full layout, then we fall back to write through MDS. Why
> dick
> around with crap that SLOWS YOU DOWN.
> 
> > Two: There are already file-layout servers out there (multiple)
> which are
> >      waiting for the Linux files-layout segment support, because the
> underline
> >      FS requires Segments and now they do not work with the Linux
> client. These
> >      are CEPH and GPFS and more.
> 
> Then they will have a _long_ wait....
> 
> Trond
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com

-- 

Matt Benjamin

The Linux Box
206 South Fifth Ave. Suite 150
Ann Arbor, MI  48104

http://linuxbox.com

tel. 734-761-4689
fax. 734-769-8938
cel. 734-216-5309

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Matt W. Benjamin]

Let me clarify: there are files based servers, our Ceph on Ganesha server is one, which have file allocation not satisfied by whole-file layouts.  I would think that demonstrating this would be sufficient to get support from the Linux client to support appropriate segment management, at any rate, if someone is willing to write and support the required code, or already has.  One of those alternatives is certainly the case.  By the way, we wrote generic pNFS, pNFS files support for Ganesha and, with a big dose of help from Panasas, are taking it to merge.

Matt

----- "Matt W. Benjamin" <matt@linuxbox.com> wrote:

> That would be pretty disappointing.  However, based on previous
> interactions, my belief would be, the
> Linux client will do what can be shown empirically to work better, or
> more correctly.
> 
> Matt
> 
> ----- "Trond Myklebust" <Trond.Myklebust@netapp.com> wrote:
> 
> > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote:
> > > On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> > > >> Also Files when they will support segments and servers that
> > request segments,
> > > >> like the CEPH server, will very much enjoy the above, .i.e:
> Tell
> > me the amount
> > > >> you know you want to write.
> > > >
> > > > Why would we want to add segment support to the pNFS files
> > client???
> > > > Segments are a nuisance that multiply the amount of unnecessary
> > chitchat
> > > > between the client and the MDS without providing any tangible
> > > > benefits...
> > > >
> > >
> > > Your kidding right?
> > >
> > > One: it is mandated by the Standard, This is not an option. So a
> > perfectly
> > >      Standard complaint server is not Supported by Linux because
> we
> > don't see
> > >      the point.
> >
> > Bollocks.. Nothing is "mandated by the Standard". If the server
> > doesn't
> > give us a full layout, then we fall back to write through MDS. Why
> > dick
> > around with crap that SLOWS YOU DOWN.
> >
> > > Two: There are already file-layout servers out there (multiple)
> > which are
> > >      waiting for the Linux files-layout segment support, because
> the
> > underline
> > >      FS requires Segments and now they do not work with the Linux
> > client. These
> > >      are CEPH and GPFS and more.
> >
> > Then they will have a _long_ wait....
> >
> > Trond
> >
> > --
> > Trond Myklebust
> > Linux NFS client maintainer
> >
> > NetApp
> > Trond.Myklebust@netapp.com
> > www.netapp.com
> 
> --
> 
> Matt Benjamin
> 
> The Linux Box
> 206 South Fifth Ave. Suite 150
> Ann Arbor, MI  48104
> 
> http://linuxbox.com
> 
> tel. 734-761-4689
> fax. 734-769-8938
> cel. 734-216-5309

-- 

Matt Benjamin

The Linux Box
206 South Fifth Ave. Suite 150
Ann Arbor, MI  48104

http://linuxbox.com

tel. 734-761-4689
fax. 734-769-8938
cel. 734-216-5309

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 19:48 -0500, Matt W. Benjamin wrote: 
> Let me clarify: there are files based servers, our Ceph on Ganesha server is one, which have file allocation not satisfied by whole-file layouts.  I would think that demonstrating this would be sufficient to get support from the Linux client to support appropriate segment management, at any rate, if someone is willing to write and support the required code, or already has.  One of those alternatives is certainly the case.  By the way, we wrote generic pNFS, pNFS files support for Ganesha and, with a big dose of help from Panasas, are taking it to merge.

I really want more than that. Please see the reply that I just sent to
Boaz: I need a client strategy for managing partial layout segments in
the case where holding a whole-file layout is not acceptable. Otherwise,
what we have now should be sufficient...

Trond

> Matt
> 
> ----- "Matt W. Benjamin" <matt@linuxbox.com> wrote:
> 
> > That would be pretty disappointing.  However, based on previous
> > interactions, my belief would be, the
> > Linux client will do what can be shown empirically to work better, or
> > more correctly.
> > 
> > Matt
> > 
> > ----- "Trond Myklebust" <Trond.Myklebust@netapp.com> wrote:
> > 
> > > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote:
> > > > On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> > > > >> Also Files when they will support segments and servers that
> > > request segments,
> > > > >> like the CEPH server, will very much enjoy the above, .i.e:
> > Tell
> > > me the amount
> > > > >> you know you want to write.
> > > > >
> > > > > Why would we want to add segment support to the pNFS files
> > > client???
> > > > > Segments are a nuisance that multiply the amount of unnecessary
> > > chitchat
> > > > > between the client and the MDS without providing any tangible
> > > > > benefits...
> > > > >
> > > >
> > > > Your kidding right?
> > > >
> > > > One: it is mandated by the Standard, This is not an option. So a
> > > perfectly
> > > >      Standard complaint server is not Supported by Linux because
> > we
> > > don't see
> > > >      the point.
> > >
> > > Bollocks.. Nothing is "mandated by the Standard". If the server
> > > doesn't
> > > give us a full layout, then we fall back to write through MDS. Why
> > > dick
> > > around with crap that SLOWS YOU DOWN.
> > >
> > > > Two: There are already file-layout servers out there (multiple)
> > > which are
> > > >      waiting for the Linux files-layout segment support, because
> > the
> > > underline
> > > >      FS requires Segments and now they do not work with the Linux
> > > client. These
> > > >      are CEPH and GPFS and more.
> > >
> > > Then they will have a _long_ wait....
> > >
> > > Trond
> > >
> > > --
> > > Trond Myklebust
> > > Linux NFS client maintainer
> > >
> > > NetApp
> > > Trond.Myklebust@netapp.com
> > > www.netapp.com
> > 
> > --
> > 
> > Matt Benjamin
> > 
> > The Linux Box
> > 206 South Fifth Ave. Suite 150
> > Ann Arbor, MI  48104
> > 
> > http://linuxbox.com
> > 
> > tel. 734-761-4689
> > fax. 734-769-8938
> > cel. 734-216-5309
> 

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Matt W. Benjamin]

I think it's reasonable that we propose a strategy or strategies for consideration, let's us do so and meet back here.

Thanks,

Matt

----- "Trond Myklebust" <Trond.Myklebust@netapp.com> wrote:

> On Tue, 2011-11-29 at 19:48 -0500, Matt W. Benjamin wrote: 
> > Let me clarify: there are files based servers, our Ceph on Ganesha
> server is one, which have file allocation not satisfied by whole-file
> layouts.  I would think that demonstrating this would be sufficient to
> get support from the Linux client to support appropriate segment
> management, at any rate, if someone is willing to write and support
> the required code, or already has.  One of those alternatives is
> certainly the case.  By the way, we wrote generic pNFS, pNFS files
> support for Ganesha and, with a big dose of help from Panasas, are
> taking it to merge.
> 
> I really want more than that. Please see the reply that I just sent
> to
> Boaz: I need a client strategy for managing partial layout segments
> in
> the case where holding a whole-file layout is not acceptable.
> Otherwise,
> what we have now should be sufficient...
> 
> Trond
> 
> > Matt
> > 
> > ----- "Matt W. Benjamin" <matt@linuxbox.com> wrote:
> > 
> > > That would be pretty disappointing.  However, based on previous
> > > interactions, my belief would be, the
> > > Linux client will do what can be shown empirically to work better,
> or
> > > more correctly.
> > > 
> > > Matt
> > > 
> > > ----- "Trond Myklebust" <Trond.Myklebust@netapp.com> wrote:
> > > 
> > > > On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote:
> > > > > On 11/29/2011 01:57 PM, Trond Myklebust wrote:
> > > > > >> Also Files when they will support segments and servers
> that
> > > > request segments,
> > > > > >> like the CEPH server, will very much enjoy the above,
> .i.e:
> > > Tell
> > > > me the amount
> > > > > >> you know you want to write.
> > > > > >
> > > > > > Why would we want to add segment support to the pNFS files
> > > > client???
> > > > > > Segments are a nuisance that multiply the amount of
> unnecessary
> > > > chitchat
> > > > > > between the client and the MDS without providing any
> tangible
> > > > > > benefits...
> > > > > >
> > > > >
> > > > > Your kidding right?
> > > > >
> > > > > One: it is mandated by the Standard, This is not an option. So
> a
> > > > perfectly
> > > > >      Standard complaint server is not Supported by Linux
> because
> > > we
> > > > don't see
> > > > >      the point.
> > > >
> > > > Bollocks.. Nothing is "mandated by the Standard". If the server
> > > > doesn't
> > > > give us a full layout, then we fall back to write through MDS.
> Why
> > > > dick
> > > > around with crap that SLOWS YOU DOWN.
> > > >
> > > > > Two: There are already file-layout servers out there
> (multiple)
> > > > which are
> > > > >      waiting for the Linux files-layout segment support,
> because
> > > the
> > > > underline
> > > > >      FS requires Segments and now they do not work with the
> Linux
> > > > client. These
> > > > >      are CEPH and GPFS and more.
> > > >
> > > > Then they will have a _long_ wait....
> > > >
> > > > Trond
> > > >
> > > > --
> > > > Trond Myklebust
> > > > Linux NFS client maintainer
> > > >
> > > > NetApp
> > > > Trond.Myklebust@netapp.com
> > > > www.netapp.com
> > > 
> > > --
> > > 
> > > Matt Benjamin
> > > 
> > > The Linux Box
> > > 206 South Fifth Ave. Suite 150
> > > Ann Arbor, MI  48104
> > > 
> > > http://linuxbox.com
> > > 
> > > tel. 734-761-4689
> > > fax. 734-769-8938
> > > cel. 734-216-5309
> > 
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com

-- 

Matt Benjamin

The Linux Box
206 South Fifth Ave. Suite 150
Ann Arbor, MI  48104

http://linuxbox.com

tel. 734-761-4689
fax. 734-769-8938
cel. 734-216-5309

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Trond Myklebust]

On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote:

> The reason Netapp don't see a point is not a factor. I have not seen a netapp
> server doing a top 100 HPC cluster either.

BTW: Stop adding this "NetApp" insinuation bullshit...

I _strongly_ resent the fact that you appear to think I'm incapable of
thinking for myself...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 03:01 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote:
> 
>> The reason Netapp don't see a point is not a factor. I have not seen a netapp
>> server doing a top 100 HPC cluster either.
> 
> BTW: Stop adding this "NetApp" insinuation bullshit...
> 
> I _strongly_ resent the fact that you appear to think I'm incapable of
> thinking for myself...
> 

OK I take that back, and apologize. Please for give me. No insult intended.

I got emotional and feared that fireworks we tend to have about the all
thing. I should have exercised more Control.

If any thing it is the opposite, I think you are a brilliant guy, and
I admire your thinking, hence my big dilemma.
 
Heart

RE: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[tao.peng]

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Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh]

On 11/29/2011 07:16 PM, tao.peng@emc.com wrote:
>> -----Original Message-----
>> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of Boaz
>> Harrosh
>> Sent: Wednesday, November 30, 2011 5:34 AM
>> To: Peng Tao
>> Cc: Trond.Myklebust@netapp.com; linux-nfs@vger.kernel.org; bhalevy@tonian.com
>> Subject: Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
>>
>> On 12/02/2011 08:52 PM, Peng Tao wrote:
>>> Issuing layoutget at .pg_init will drop the IO size information and ask for 4KB
>>> layout every time. However, the IO size information is very valuable for MDS to
>>> determine how much layout it should return to client.
>>>
>>> The patchset try to allow LD not to send layoutget at .pg_init but instead at
>>> pnfs_do_multiple_writes. So that real IO size is preserved and sent to MDS.
>>>
>>> Tests against a server that does not aggressively pre-allocate layout, shows
>>> that the IO size informantion is really useful to block layout MDS.
>>>
>>> The generic pnfs layer changes are trival to file layout and object as long as
>>> they still send layoutget at .pg_init.
>>>
>>
>> I have a better solution for your problem. Which is a much smaller a change and
>> I think gives you much better heuristics.
>>
>> Keep the layout_get exactly where it is, but instead of sending PAGE_SIZE send
>> the amount of dirty pages you have.
>>
>> If it is a linear write you will be exact on the money with a single lo_get. If
>> it is an heavy random write then you might need more lo_gets and you might be getting
>> some unused segments. But heavy random write is rare and slow anyway. As a first
>> approximation its fine. (We can later fix that as well)
>
> I would say no to the above... For objects/files MDS, it may not hurt
> much to allocate wasting layout. But for blocklayout server, each
> layout allocation consumes much more resource than just giving out
> stripping information like objects/files. 

That's fine, for the linear IO like iozone below my way is just the same
as yours. For the random IO I'm not sure how much better will your solution
be. Not by much.

I want a solution for objects as well. But I cannot use yours because I need
a layout before the final request consolidation. Solve my problem too.

> So helping MDS to do the
> correct decision is the right thing for client to do.

I agree. All I'm saying is that there is available information at the time
of .pg_init to send that number just fine. Have you looked? it's all there
NFS core can tell you how many pages have passed ->write_pages.

> 
>>
>> The .pg_init is done after .write_pages call from VFS and all the to-be-written
>> pages are already staged to be written. So there should be a way to easily extract
>> that information.
>>
>>> iozone cmd:
>>> ./iozone -r 1m -s 4G -w -W -c -t 10 -i 0 -F /mnt/iozone.data.1 /mnt/iozone.data.2 /mnt/iozone.data.3
>> /mnt/iozone.data.4 /mnt/iozone.data.5 /mnt/iozone.data.6 /mnt/iozone.data.7 /mnt/iozone.data.8
>> /mnt/iozone.data.9 /mnt/iozone.data.10
>>>
>>> Befor patch: around 12MB/s throughput
>>> After patch: around 72MB/s throughput
>>>
>>
>> Yes Yes that stupid Brain dead Server is no indication for anything. The server
>> should know best about optimal sizes and layouts. Please don't give me that stuff
>> again.
>>
> Actually the server is already doing layout pre-allocation. It is
> just that it doesn't know what client really wants so cannot do it
> too aggressively. That's why I wanted to make client to send the REAL
> IO size information to server. From performance perspective, dropping
> IO size information is always a BAD THING(TM) to do.

I totally agree. I want it too. There is a way to do it in pg_init time
all the information is there it only needs to be passed to layout_get.

> 
>> BTW don't limit the lo_segment size by the max_io_size. This is why you
>> have .bg_test to signal when IO is maxed out.
>>
> Actually lo_segment size is never limited by max_io_size. Server is
> always entitled to send larger layout than client asks from.

You miss my point. In your last patch you have

+/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
+#define PNFSBLK_MAXRSIZE (0x1<<22)
+#define PNFSBLK_MAXWSIZE (0x1<<21)

I don't know what these number mean but they kind of look like IO limits
and not segment limits. If I'm wrong then sorry. What are these numbers?

If a client has 1G of dirty pages to write why not get the full layout
at once. Where does the 4M limit comes from?

> 
>> - The read segments should be as big as possible (i_size long)
>> - The Write segments should ideally be as big as the Application
>>   wants to write to. (Amount of dirty pages at time of nfs-write-out
>>   is a very good first approximation).
>>
>> So I guess it is: I hate these patches, to much mess, too little goodness.
> I'm afraid I can't agree with you...
> 

Sure you do. You did the hard work and now I'm telling you you need to do
more work. I'm sorry for that. But I want a solution for me and I think
there is a simple solution that will satisfy both of our needs.

Sorry for that. If I had time I would do it. Only I have harder real BUGS
to fix on my plate.

If you could look into it It will be very nice. And thank you for working
on this so far. Only that current solution is not optimal and I will need
to continue on it later, if left as is.

> Thanks,
> Tao
> 

Thanks

RE: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[tao.peng]

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Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Benny Halevy]

On 2011-11-30 07:05, tao.peng@emc.com wrote:
>> -----Original Message-----
>> From: Boaz Harrosh [mailto:bharrosh@panasas.com]
>> Sent: Wednesday, November 30, 2011 11:51 AM
>> To: Peng, Tao
>> Cc: bergwolf@gmail.com; Trond.Myklebust@netapp.com; linux-nfs@vger.kernel.org; bhalevy@tonian.com
>> Subject: Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
>>
>> On 11/29/2011 07:16 PM, tao.peng@emc.com wrote:
>>>> -----Original Message-----
>>>> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of Boaz
>>>> Harrosh
>>>> Sent: Wednesday, November 30, 2011 5:34 AM
>>>> To: Peng Tao
>>>> Cc: Trond.Myklebust@netapp.com; linux-nfs@vger.kernel.org; bhalevy@tonian.com
>>>> Subject: Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes
>>>>
>>>> On 12/02/2011 08:52 PM, Peng Tao wrote:
>>>>> Issuing layoutget at .pg_init will drop the IO size information and ask for 4KB
>>>>> layout every time. However, the IO size information is very valuable for MDS to
>>>>> determine how much layout it should return to client.
>>>>>
>>>>> The patchset try to allow LD not to send layoutget at .pg_init but instead at
>>>>> pnfs_do_multiple_writes. So that real IO size is preserved and sent to MDS.
>>>>>
>>>>> Tests against a server that does not aggressively pre-allocate layout, shows
>>>>> that the IO size informantion is really useful to block layout MDS.
>>>>>
>>>>> The generic pnfs layer changes are trival to file layout and object as long as
>>>>> they still send layoutget at .pg_init.
>>>>>
>>>>
>>>> I have a better solution for your problem. Which is a much smaller a change and
>>>> I think gives you much better heuristics.
>>>>
>>>> Keep the layout_get exactly where it is, but instead of sending PAGE_SIZE send
>>>> the amount of dirty pages you have.
>>>>
>>>> If it is a linear write you will be exact on the money with a single lo_get. If
>>>> it is an heavy random write then you might need more lo_gets and you might be getting
>>>> some unused segments. But heavy random write is rare and slow anyway. As a first
>>>> approximation its fine. (We can later fix that as well)
>>>
>>> I would say no to the above... For objects/files MDS, it may not hurt
>>> much to allocate wasting layout. But for blocklayout server, each
>>> layout allocation consumes much more resource than just giving out
>>> stripping information like objects/files.
>>
>> That's fine, for the linear IO like iozone below my way is just the same
>> as yours. For the random IO I'm not sure how much better will your solution
>> be. Not by much.
> As I said, for random IO, there will be much disk space wasting on blocklayout server in your solution. That's why I don't agree with it. Besides, in some cases, server may be put in a hard position to determine if the IO is really linear or in fact random in your solution.
> 
>>
>> I want a solution for objects as well. But I cannot use yours because I need
>> a layout before the final request consolidation. Solve my problem too.
>>
> I used to look at objects at some time, and as I remember, it need max io size in each lseg to finish .pg_test. Is this the reason you need a layout before the final request consolidation? Does the value vary in different lseg?
> 
>>> So helping MDS to do the
>>> correct decision is the right thing for client to do.
>>
>> I agree. All I'm saying is that there is available information at the time
>> of .pg_init to send that number just fine. Have you looked? it's all there
>> NFS core can tell you how many pages have passed ->write_pages.
>>
> It only tells a fake IO size for the number of dirty pages. No one can promise these pages are all continuous. Instead, if we can give a real IO size, why refuse to do it?
> 

I agree. The client need not blindly extend loga_length.
Simply ask for what you need and let the server optimize the result.

Benny

>>>
>>>>
>>>> The .pg_init is done after .write_pages call from VFS and all the to-be-written
>>>> pages are already staged to be written. So there should be a way to easily extract
>>>> that information.
>>>>
>>>>> iozone cmd:
>>>>> ./iozone -r 1m -s 4G -w -W -c -t 10 -i 0 -F /mnt/iozone.data.1 /mnt/iozone.data.2
>> /mnt/iozone.data.3
>>>> /mnt/iozone.data.4 /mnt/iozone.data.5 /mnt/iozone.data.6 /mnt/iozone.data.7 /mnt/iozone.data.8
>>>> /mnt/iozone.data.9 /mnt/iozone.data.10
>>>>>
>>>>> Befor patch: around 12MB/s throughput
>>>>> After patch: around 72MB/s throughput
>>>>>
>>>>
>>>> Yes Yes that stupid Brain dead Server is no indication for anything. The server
>>>> should know best about optimal sizes and layouts. Please don't give me that stuff
>>>> again.
>>>>
>>> Actually the server is already doing layout pre-allocation. It is
>>> just that it doesn't know what client really wants so cannot do it
>>> too aggressively. That's why I wanted to make client to send the REAL
>>> IO size information to server. From performance perspective, dropping
>>> IO size information is always a BAD THING(TM) to do.
>>
>> I totally agree. I want it too. There is a way to do it in pg_init time
>> all the information is there it only needs to be passed to layout_get.
>>
> This "all the information is there" is likely to be false, unless you only deal with sequential IO...
> 
>>>
>>>> BTW don't limit the lo_segment size by the max_io_size. This is why you
>>>> have .bg_test to signal when IO is maxed out.
>>>>
>>> Actually lo_segment size is never limited by max_io_size. Server is
>>> always entitled to send larger layout than client asks from.
>>
>> You miss my point. In your last patch you have
>>
>> +/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
>> +#define PNFSBLK_MAXRSIZE (0x1<<22)
>> +#define PNFSBLK_MAXWSIZE (0x1<<21)
>>
>> I don't know what these number mean but they kind of look like IO limits
>> and not segment limits. If I'm wrong then sorry. What are these numbers?
>>
> Yes, these are io size limit. I should just remove the comments that are totally misleading.
> 
>> If a client has 1G of dirty pages to write why not get the full layout
>> at once. Where does the 4M limit comes from?
>>
> Please note that block layout server cannot just give full file stripping information. When we ask for 1GB layout, most times we get much less anyway. And the value of 2MB comes from our experience with MPFS, to allow the balance between server pressure and client performance.
> 
> Also, currently we retry MDS on a per nfs_read/write_data basis. It is much easier to handle 2MB rather than 1GB dirty pages. I notice that it may not be an issue for objects as you have max IO size limit on every lseg.
> 
>>>
>>>> - The read segments should be as big as possible (i_size long)
>>>> - The Write segments should ideally be as big as the Application
>>>>   wants to write to. (Amount of dirty pages at time of nfs-write-out
>>>>   is a very good first approximation).
>>>>
>>>> So I guess it is: I hate these patches, to much mess, too little goodness.
>>> I'm afraid I can't agree with you...
>>>
>>
>> Sure you do. You did the hard work and now I'm telling you you need to do
>> more work. I'm sorry for that. But I want a solution for me and I think
>> there is a simple solution that will satisfy both of our needs.
>>
> Sorry but I don't think your solution is good enough to address blocklayout's concerns. It would be great if we can utilize the same solution. But when we do need, I think it perfectly reasonable to let blocklayout and object layout have different strategy on layoutget, based on the fact that our servers have different behavior on layout allocation. And allowing this kind of difference is exactly what strcut nfs_pageio_ops serves for.
> 
> What do you think?
> 
> Thanks,
> Tao
>> Sorry for that. If I had time I would do it. Only I have harder real BUGS
>> to fix on my plate.
>>
>> If you could look into it It will be very nice. And thank you for working
>> on this so far. Only that current solution is not optimal and I will need
>> to continue on it later, if left as is.
>>
>>> Thanks,
>>> Tao
>>>
>>
>> Thanks
> 
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[PATCH 1/4] nfsv41: export pnfs_find_alloc_layout

[Peng Tao]

So that layout driver can access layout header when there is none.

Signed-off-by: Peng Tao <peng_tao@emc.com>
---
 fs/nfs/pnfs.c |    3 ++-
 fs/nfs/pnfs.h |    4 ++++
 2 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index baf7353..3be29c7 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -848,7 +848,7 @@ alloc_init_layout_hdr(struct inode *ino,
 	return lo;
 }
 
-static struct pnfs_layout_hdr *
+struct pnfs_layout_hdr *
 pnfs_find_alloc_layout(struct inode *ino,
 		       struct nfs_open_context *ctx,
 		       gfp_t gfp_flags)
@@ -875,6 +875,7 @@ pnfs_find_alloc_layout(struct inode *ino,
 		pnfs_free_layout_hdr(new);
 	return nfsi->layout;
 }
+EXPORT_SYMBOL_GPL(pnfs_find_alloc_layout);
 
 /*
  * iomode matching rules:
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 1509530..9614ac9 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -209,6 +209,10 @@ struct pnfs_layout_segment *pnfs_update_layout(struct inode *ino,
 					       u64 count,
 					       enum pnfs_iomode iomode,
 					       gfp_t gfp_flags);
+struct pnfs_layout_hdr *
+pnfs_find_alloc_layout(struct inode *ino,
+		       struct nfs_open_context *ctx,
+		       gfp_t gfp_flags);
 
 void nfs4_deviceid_mark_client_invalid(struct nfs_client *clp);
 
-- 
1.7.1.262.g5ef3d

[PATCH 2/4] nfsv41: add and export pnfs_find_get_layout_locked

[Peng Tao]

It tries to find the lseg from local cache but not retrive layout from server.

Signed-off-by: Peng Tao <peng_tao@emc.com>
---
 fs/nfs/pnfs.c |   25 +++++++++++++++++++++++++
 fs/nfs/pnfs.h |    5 +++++
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 3be29c7..734e670 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -933,6 +933,31 @@ pnfs_find_lseg(struct pnfs_layout_hdr *lo,
 }
 
 /*
+ * Find and reference lseg with ino->i_lock held.
+ */
+struct pnfs_layout_segment *
+pnfs_find_get_layout_locked(struct inode *ino,
+			loff_t pos,
+			u64 count,
+			enum pnfs_iomode iomode)
+{
+	struct pnfs_layout_segment *lseg = NULL;
+	struct pnfs_layout_range range = {
+		.iomode = iomode,
+		.offset = pos,
+		.length = count,
+	};
+
+	if (NFS_I(ino)->layout == NULL)
+		goto out;
+
+	lseg = pnfs_find_lseg(NFS_I(ino)->layout, &range);
+out:
+	return lseg;
+}
+EXPORT_SYMBOL_GPL(pnfs_find_get_layout_locked);
+
+/*
  * Layout segment is retreived from the server if not cached.
  * The appropriate layout segment is referenced and returned to the caller.
  */
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 9614ac9..0c55fc1 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -213,6 +213,11 @@ struct pnfs_layout_hdr *
 pnfs_find_alloc_layout(struct inode *ino,
 		       struct nfs_open_context *ctx,
 		       gfp_t gfp_flags);
+struct pnfs_layout_segment *
+pnfs_find_get_layout_locked(struct inode *ino,
+			loff_t pos,
+			u64 count,
+			enum pnfs_iomode iomode);
 
 void nfs4_deviceid_mark_client_invalid(struct nfs_client *clp);
 
-- 
1.7.1.262.g5ef3d

[PATCH 3/4] nfsv41: get lseg before issue LD IO if pgio doesn't carry lseg

[Peng Tao]

This gives LD option not to ask for layout in pg_init.

Signed-off-by: Peng Tao <peng_tao@emc.com>
---
 fs/nfs/pnfs.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 734e670..c8dc0b1 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1254,6 +1254,7 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
 	struct nfs_write_data *data;
 	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
 	struct pnfs_layout_segment *lseg = desc->pg_lseg;
+	const bool has_lseg = !!lseg;
 
 	desc->pg_lseg = NULL;
 	while (!list_empty(head)) {
@@ -1262,7 +1263,29 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
 		data = list_entry(head->next, struct nfs_write_data, list);
 		list_del_init(&data->list);
 
+		if (!has_lseg) {
+			struct nfs_page *req = nfs_list_entry(data->pages.next);
+			__u64 length = data->npages << PAGE_CACHE_SHIFT;
+
+			lseg = pnfs_update_layout(desc->pg_inode,
+						  req->wb_context,
+						  req_offset(req),
+						  length,
+						  IOMODE_RW,
+						  GFP_NOFS);
+			if (!lseg || length > (lseg->pls_range.length)) {
+				put_lseg(lseg);
+				lseg = NULL;
+				pnfs_write_through_mds(desc,data);
+				continue;
+			}
+		}
+
 		trypnfs = pnfs_try_to_write_data(data, call_ops, lseg, how);
+		if (!has_lseg) {
+			put_lseg(lseg);
+			lseg = NULL;
+		}
 		if (trypnfs == PNFS_NOT_ATTEMPTED)
 			pnfs_write_through_mds(desc, data);
 	}
@@ -1350,6 +1373,7 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
 	struct nfs_read_data *data;
 	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
 	struct pnfs_layout_segment *lseg = desc->pg_lseg;
+	const bool has_lseg = !!lseg;
 
 	desc->pg_lseg = NULL;
 	while (!list_empty(head)) {
@@ -1358,7 +1382,29 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
 		data = list_entry(head->next, struct nfs_read_data, list);
 		list_del_init(&data->list);
 
+		if (!has_lseg) {
+			struct nfs_page *req = nfs_list_entry(data->pages.next);
+			__u64 length = data->npages << PAGE_CACHE_SHIFT;
+
+			lseg = pnfs_update_layout(desc->pg_inode,
+						  req->wb_context,
+						  req_offset(req),
+						  length,
+						  IOMODE_READ,
+						  GFP_KERNEL);
+			if (!lseg || length > lseg->pls_range.length) {
+				put_lseg(lseg);
+				lseg = NULL;
+				pnfs_read_through_mds(desc, data);
+				continue;
+			}
+		}
+
 		trypnfs = pnfs_try_to_read_data(data, call_ops, lseg);
+		if (!has_lseg) {
+			put_lseg(lseg);
+			lseg = NULL;
+		}
 		if (trypnfs == PNFS_NOT_ATTEMPTED)
 			pnfs_read_through_mds(desc, data);
 	}
-- 
1.7.1.262.g5ef3d

Re: [PATCH 3/4] nfsv41: get lseg before issue LD IO if pgio doesn't carry lseg

[Benny Halevy]

On 2011-12-03 06:52, Peng Tao wrote:
> This gives LD option not to ask for layout in pg_init.
> 
> Signed-off-by: Peng Tao <peng_tao@emc.com>
> ---
>  fs/nfs/pnfs.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 46 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 734e670..c8dc0b1 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -1254,6 +1254,7 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
>  	struct nfs_write_data *data;
>  	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
>  	struct pnfs_layout_segment *lseg = desc->pg_lseg;
> +	const bool has_lseg = !!lseg;

nit: "has_lseg = (lseg != NULL)" would be more straight forward IMO

>  
>  	desc->pg_lseg = NULL;
>  	while (!list_empty(head)) {
> @@ -1262,7 +1263,29 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
>  		data = list_entry(head->next, struct nfs_write_data, list);
>  		list_del_init(&data->list);
>  
> +		if (!has_lseg) {
> +			struct nfs_page *req = nfs_list_entry(data->pages.next);
> +			__u64 length = data->npages << PAGE_CACHE_SHIFT;
> +
> +			lseg = pnfs_update_layout(desc->pg_inode,
> +						  req->wb_context,
> +						  req_offset(req),
> +						  length,
> +						  IOMODE_RW,
> +						  GFP_NOFS);
> +			if (!lseg || length > (lseg->pls_range.length)) {

I'm concerned about the 'length' part of this condition.
pnfs_try_to_write_data should handle short writes/reads and
we should be able to iterate through the I/O using different
layout segments.

> +				put_lseg(lseg);
> +				lseg = NULL;
> +				pnfs_write_through_mds(desc,data);
> +				continue;
> +			}
> +		}
> +
>  		trypnfs = pnfs_try_to_write_data(data, call_ops, lseg, how);
> +		if (!has_lseg) {
> +			put_lseg(lseg);
> +			lseg = NULL;
> +		}

We had an implementation in the past that saved the most recent lseg in 'desc'
so it could be used for the remaining requests.  Once exhausted, you can
look for a new one.

>  		if (trypnfs == PNFS_NOT_ATTEMPTED)
>  			pnfs_write_through_mds(desc, data);
>  	}
> @@ -1350,6 +1373,7 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
>  	struct nfs_read_data *data;
>  	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
>  	struct pnfs_layout_segment *lseg = desc->pg_lseg;
> +	const bool has_lseg = !!lseg;

ditto

>  
>  	desc->pg_lseg = NULL;
>  	while (!list_empty(head)) {
> @@ -1358,7 +1382,29 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
>  		data = list_entry(head->next, struct nfs_read_data, list);
>  		list_del_init(&data->list);
>  
> +		if (!has_lseg) {
> +			struct nfs_page *req = nfs_list_entry(data->pages.next);
> +			__u64 length = data->npages << PAGE_CACHE_SHIFT;
> +
> +			lseg = pnfs_update_layout(desc->pg_inode,
> +						  req->wb_context,
> +						  req_offset(req),
> +						  length,
> +						  IOMODE_READ,
> +						  GFP_KERNEL);
> +			if (!lseg || length > lseg->pls_range.length) {
> +				put_lseg(lseg);
> +				lseg = NULL;
> +				pnfs_read_through_mds(desc, data);
> +				continue;
> +			}
> +		}
> +
>  		trypnfs = pnfs_try_to_read_data(data, call_ops, lseg);
> +		if (!has_lseg) {
> +			put_lseg(lseg);
> +			lseg = NULL;
> +		}

ditto

Benny

>  		if (trypnfs == PNFS_NOT_ATTEMPTED)
>  			pnfs_read_through_mds(desc, data);
>  	}

Re: [PATCH 3/4] nfsv41: get lseg before issue LD IO if pgio doesn't carry lseg

[Peng Tao]

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[PATCH 4/4] pnfsblock: do ask for layout in pg_init

[Peng Tao]

Asking for layout in pg_init will always make client ask for only 4KB
layout in every layoutget. This way, client drops the IO size information
that is meaningful for MDS in handing out layout.

In stead, if layout is not find in cache, do not send layoutget
at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
because that is where we know the real size of current IO. By telling the
real IO size to MDS, MDS will have a better chance to give proper layout.

Signed-off-by: Peng Tao <peng_tao@emc.com>
---
 fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++++++++++++-
 1 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 48cfac3..fd585fe 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -39,6 +39,7 @@
 #include <linux/prefetch.h>
 
 #include "blocklayout.h"
+#include "../internal.h"
 
 #define NFSDBG_FACILITY	NFSDBG_PNFS_LD
 
@@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
 	return 0;
 }
 
+/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
+#define PNFSBLK_MAXRSIZE (0x1<<22)
+#define PNFSBLK_MAXWSIZE (0x1<<21)
+static void
+bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_read_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXRSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_READ);
+	spin_unlock(&ino->i_lock);
+}
+
+static void
+bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_write_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXWSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_RW);
+	spin_unlock(&ino->i_lock);
+}
+
 static const struct nfs_pageio_ops bl_pg_read_ops = {
-	.pg_init = pnfs_generic_pg_init_read,
+	.pg_init = bl_pg_init_read,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_readpages,
 };
 
 static const struct nfs_pageio_ops bl_pg_write_ops = {
-	.pg_init = pnfs_generic_pg_init_write,
+	.pg_init = bl_pg_init_write,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_writepages,
 };
-- 
1.7.1.262.g5ef3d

Re: [PATCH 4/4] pnfsblock: do ask for layout in pg_init

[Trond Myklebust]

On Fri, 2011-12-02 at 20:52 -0800, Peng Tao wrote: 
> Asking for layout in pg_init will always make client ask for only 4KB
> layout in every layoutget. This way, client drops the IO size information
> that is meaningful for MDS in handing out layout.
> 
> In stead, if layout is not find in cache, do not send layoutget
> at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
> because that is where we know the real size of current IO. By telling the
> real IO size to MDS, MDS will have a better chance to give proper layout.

Why can't you just split pnfs_update_layout() into 2 sub-functions
instead of duplicating it in private block code?

Then call layoutget in your pg_doio() callback instead of adding a
redundant pnfs_update_layout to
pnfs_do_multiple_reads/pnfs_do_multiple_writes...


> Signed-off-by: Peng Tao <peng_tao@emc.com>
> ---
>  fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++++++++++++-
>  1 files changed, 52 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index 48cfac3..fd585fe 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -39,6 +39,7 @@
>  #include <linux/prefetch.h>
>  
>  #include "blocklayout.h"
> +#include "../internal.h"
>  
>  #define NFSDBG_FACILITY	NFSDBG_PNFS_LD
>  
> @@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
>  	return 0;
>  }
>  
> +/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
> +#define PNFSBLK_MAXRSIZE (0x1<<22)
> +#define PNFSBLK_MAXWSIZE (0x1<<21)
> +static void
> +bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
> +{
> +	struct inode *ino = pgio->pg_inode;
> +	struct pnfs_layout_hdr *lo;
> +
> +	BUG_ON(pgio->pg_lseg != NULL);
> +	spin_lock(&ino->i_lock);
> +	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);

This has never been tested... It contains all sorts of bugs from
recursive attempts to take the ino->i_lock, to sleep-under-spinlock...

> +	if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
> +		spin_unlock(&ino->i_lock);
> +		nfs_pageio_reset_read_mds(pgio);
> +		return;
> +	}
> +
> +	pgio->pg_bsize = PNFSBLK_MAXRSIZE;
> +	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
> +						req_offset(req),
> +						req->wb_bytes,
> +						IOMODE_READ);
> +	spin_unlock(&ino->i_lock);
> +}
> +
> +static void
> +bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
> +{
> +	struct inode *ino = pgio->pg_inode;
> +	struct pnfs_layout_hdr *lo;
> +
> +	BUG_ON(pgio->pg_lseg != NULL);
> +	spin_lock(&ino->i_lock);
> +	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
> +	if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
> +		spin_unlock(&ino->i_lock);
> +		nfs_pageio_reset_write_mds(pgio);
> +		return;
> +	}

Ditto...

> +
> +	pgio->pg_bsize = PNFSBLK_MAXWSIZE;
> +	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
> +						req_offset(req),
> +						req->wb_bytes,
> +						IOMODE_RW);
> +	spin_unlock(&ino->i_lock);
> +}
> +
>  static const struct nfs_pageio_ops bl_pg_read_ops = {
> -	.pg_init = pnfs_generic_pg_init_read,
> +	.pg_init = bl_pg_init_read,
>  	.pg_test = pnfs_generic_pg_test,
>  	.pg_doio = pnfs_generic_pg_readpages,
>  };
>  
>  static const struct nfs_pageio_ops bl_pg_write_ops = {
> -	.pg_init = pnfs_generic_pg_init_write,
> +	.pg_init = bl_pg_init_write,
>  	.pg_test = pnfs_generic_pg_test,
>  	.pg_doio = pnfs_generic_pg_writepages,
>  };

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

Re: [PATCH 4/4] pnfsblock: do ask for layout in pg_init

[Peng Tao]

On Wed, Nov 30, 2011 at 12:40 AM, Trond Myklebust
<Trond.Myklebust@netapp.com> wrote:
> On Fri, 2011-12-02 at 20:52 -0800, Peng Tao wrote:
>> Asking for layout in pg_init will always make client ask for only 4KB
>> layout in every layoutget. This way, client drops the IO size information
>> that is meaningful for MDS in handing out layout.
>>
>> In stead, if layout is not find in cache, do not send layoutget
>> at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
>> because that is where we know the real size of current IO. By telling the
>> real IO size to MDS, MDS will have a better chance to give proper layout.
>
> Why can't you just split pnfs_update_layout() into 2 sub-functions
> instead of duplicating it in private block code?
Because I wanted to differentiate between no layout header and no
cached lseg, where the pnfs_update_layout() interface is not enough to
tell the difference. Of course I can put these all into generic layer.
I will update the patchset to do it.

>
> Then call layoutget in your pg_doio() callback instead of adding a
> redundant pnfs_update_layout to
> pnfs_do_multiple_reads/pnfs_do_multiple_writes...
I have considered it before but using private pg_doio() means we will
have as much duplication of pnfs_generic_pg_read/writepages.

>
>
>> Signed-off-by: Peng Tao <peng_tao@emc.com>
>> ---
>>  fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++++++++++++-
>>  1 files changed, 52 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
>> index 48cfac3..fd585fe 100644
>> --- a/fs/nfs/blocklayout/blocklayout.c
>> +++ b/fs/nfs/blocklayout/blocklayout.c
>> @@ -39,6 +39,7 @@
>>  #include <linux/prefetch.h>
>>
>>  #include "blocklayout.h"
>> +#include "../internal.h"
>>
>>  #define NFSDBG_FACILITY      NFSDBG_PNFS_LD
>>
>> @@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
>>       return 0;
>>  }
>>
>> +/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
>> +#define PNFSBLK_MAXRSIZE (0x1<<22)
>> +#define PNFSBLK_MAXWSIZE (0x1<<21)
>> +static void
>> +bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>> +{
>> +     struct inode *ino = pgio->pg_inode;
>> +     struct pnfs_layout_hdr *lo;
>> +
>> +     BUG_ON(pgio->pg_lseg != NULL);
>> +     spin_lock(&ino->i_lock);
>> +     lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);
>
> This has never been tested... It contains all sorts of bugs from
> recursive attempts to take the ino->i_lock, to sleep-under-spinlock...
The code is certainly tested... If you look into
pnfs_find_alloc_layout(), you'll see the spinlock is released inside
pnfs_find_alloc_layout() when it needs to sleep there.
pnfs_find_alloc_layout() actually asserts spin_locked at function
entrance... So we have to take the spin lock before calling it...

 851 static struct pnfs_layout_hdr *
 852 pnfs_find_alloc_layout(struct inode *ino,
 853                        struct nfs_open_context *ctx,
 854                        gfp_t gfp_flags)
 855 {
 856         struct nfs_inode *nfsi = NFS_I(ino);
 857         struct pnfs_layout_hdr *new = NULL;
 858
 859         dprintk("%s Begin ino=%p layout=%p\n", __func__, ino,
nfsi->layout);
 860
 861         assert_spin_locked(&ino->i_lock);
 862         if (nfsi->layout) {
 863                 if (test_bit(NFS_LAYOUT_DESTROYED,
&nfsi->layout->plh_flags))
 864                         return NULL;
 865                 else
 866                         return nfsi->layout;
 867         }
 868         spin_unlock(&ino->i_lock);
 869         new = alloc_init_layout_hdr(ino, ctx, gfp_flags);
 870         spin_lock(&ino->i_lock);
 871
 872         if (likely(nfsi->layout == NULL))       /* Won the race? */
 873                 nfsi->layout = new;
 874         else
 875                 pnfs_free_layout_hdr(new);
 876         return nfsi->layout;
 877 }

-- 
Thanks,
Tao
>
>> +     if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
>> +             spin_unlock(&ino->i_lock);
>> +             nfs_pageio_reset_read_mds(pgio);
>> +             return;
>> +     }
>> +
>> +     pgio->pg_bsize = PNFSBLK_MAXRSIZE;
>> +     pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
>> +                                             req_offset(req),
>> +                                             req->wb_bytes,
>> +                                             IOMODE_READ);
>> +     spin_unlock(&ino->i_lock);
>> +}
>> +
>> +static void
>> +bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>> +{
>> +     struct inode *ino = pgio->pg_inode;
>> +     struct pnfs_layout_hdr *lo;
>> +
>> +     BUG_ON(pgio->pg_lseg != NULL);
>> +     spin_lock(&ino->i_lock);
>> +     lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
>> +     if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
>> +             spin_unlock(&ino->i_lock);
>> +             nfs_pageio_reset_write_mds(pgio);
>> +             return;
>> +     }
>
> Ditto...
>
>> +
>> +     pgio->pg_bsize = PNFSBLK_MAXWSIZE;
>> +     pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
>> +                                             req_offset(req),
>> +                                             req->wb_bytes,
>> +                                             IOMODE_RW);
>> +     spin_unlock(&ino->i_lock);
>> +}
>> +
>>  static const struct nfs_pageio_ops bl_pg_read_ops = {
>> -     .pg_init = pnfs_generic_pg_init_read,
>> +     .pg_init = bl_pg_init_read,
>>       .pg_test = pnfs_generic_pg_test,
>>       .pg_doio = pnfs_generic_pg_readpages,
>>  };
>>
>>  static const struct nfs_pageio_ops bl_pg_write_ops = {
>> -     .pg_init = pnfs_generic_pg_init_write,
>> +     .pg_init = bl_pg_init_write,
>>       .pg_test = pnfs_generic_pg_test,
>>       .pg_doio = pnfs_generic_pg_writepages,
>>  };
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com
>

Re: [PATCH 4/4] pnfsblock: do ask for layout in pg_init

[Trond Myklebust]

On Wed, 2011-11-30 at 01:25 +0800, Peng Tao wrote: 
> On Wed, Nov 30, 2011 at 12:40 AM, Trond Myklebust
> <Trond.Myklebust@netapp.com> wrote:
> > On Fri, 2011-12-02 at 20:52 -0800, Peng Tao wrote:
> >> Asking for layout in pg_init will always make client ask for only 4KB
> >> layout in every layoutget. This way, client drops the IO size information
> >> that is meaningful for MDS in handing out layout.
> >>
> >> In stead, if layout is not find in cache, do not send layoutget
> >> at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
> >> because that is where we know the real size of current IO. By telling the
> >> real IO size to MDS, MDS will have a better chance to give proper layout.
> >
> > Why can't you just split pnfs_update_layout() into 2 sub-functions
> > instead of duplicating it in private block code?
> Because I wanted to differentiate between no layout header and no
> cached lseg, where the pnfs_update_layout() interface is not enough to
> tell the difference. Of course I can put these all into generic layer.
> I will update the patchset to do it.
> 
> >
> > Then call layoutget in your pg_doio() callback instead of adding a
> > redundant pnfs_update_layout to
> > pnfs_do_multiple_reads/pnfs_do_multiple_writes...
> I have considered it before but using private pg_doio() means we will
> have as much duplication of pnfs_generic_pg_read/writepages.

Why? All you need to do is send the layoutget, and then call the
existing pnfs_generic_pg_read/writepages?

The difference here is that you're adding that step into
pnfs_generic_pg_read/writepages in patch 3/4. Basically you are adding
block-specific code into an otherwise generic function instead of doing
it cleanly in the block-specific callbacks.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

RE: [PATCH 4/4] pnfsblock: do ask for layout in pg_init

[tao.peng]

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