Current topics for LSF10/MM Summit 8-9 August in Boston

Current topics for LSF10/MM Summit 8-9 August in Boston

[James Bottomley]

Given that we're under two months out, I thought it would be time to
post a summary of the topics we've collected so far (Nick will post the
MM summit ones later).  Look this over, and if there's anything missing,
propose it ... or if you have cross Storage/FS/MM topics, post them too.

Oh, and since we're not the most organised bunch, if you posted a topic
and don't see it in the list, please resend ... we probably lost it in
an email shuffle.

Current Filesystem Topics:

Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
Anshul Madan	reflink for NFS
Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
James Lentini	reflink for NFS
Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
Michael Rubin	Writeback scaling
Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
Al Viro	Sorting out d_revalidate and other dcache issues
Coly Li		directory/large file scalability
Sorin Faibish	Cache writeback discussion

Current Storage Topics:

Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
Hannes Reinecke	libfc/multipath/error handing
James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
Jeff Moyer	IO scheduler
Joel Becker	SAN management plugin
Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME

Plus some MM summit ones which Nick will summarise.

For the benefit of those who've forgotten here's the original Call for
topics and attendees:

This year we'll hold the Linux Storage and Filesystems summit jointly
with the VM summit on the two days before LinuxCon in Boston (that's
Sunday and Monday) at the Renaissance Hotel:

http://events.linuxfoundation.org/events/linuxcon

We're planning to hold some sessions jointly and split into three tracks
(Filesystems, Storage and VM) for others, so we're encouraging proposals
for discussion that cover areas relevant to all three groups as well as
more specific technical topics.

Suggestions for agenda topics should be sent to

lsf10-pc@lists.linuxfoundation.org

and optionally cc the Linux list which would be most interested in it:

SCSI: linux-scsi@vger.kernel.org
FS: linux-fsdevel@vger.kernel.org (plus relevant fs specific list)
MM: linux-mm@kvack.org

Please tag your subject with [LSF/VM TOPIC] so those of us who're not
very organised can find them easily in our inboxes.  The agenda topics
and attendees will be selected by the programme committee, but the final
agenda will be by formed by consensus of the attendees on the day.

We'll try to cap attendance at around 20 per track to facilitate
discussions although the final numbers will depend on the room sizes
at the venue.

Requests to attend should be sent to:

lsf10-pc@lists.linuxfoundation.org

please summarise what you'll bring to the meeting, and what you'd like
to discuss.  please also tag your email with [ATTEND] so there's less
chance of it getting lost in the large mail pile.

Presentations are allowed to guide discussion, but are strongly
discouraged.  There will be no recording or audio bridge, however
written minutes will be published as in previous years:

2009:
http://lwn.net/Articles/327601/
http://lwn.net/Articles/327740/
http://lwn.net/Articles/328347/

Prior years:
http://www.usenix.org/events/lsf08/tech/lsf08sums.pdf
http://www.usenix.org/publications/login/2007-06/openpdfs/lsf07sums.pdf

If you have feedback on last year's meeting that we can use to improve
this year's, please also send that to:

lsf10-pc@lists.linuxfoundation.org

Thanks,

James Bottomley


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Current topics for LSF10/MM Summit 8-9 August in Boston

[James Bottomley]

Given that we're under two months out, I thought it would be time to
post a summary of the topics we've collected so far (Nick will post the
MM summit ones later).  Look this over, and if there's anything missing,
propose it ... or if you have cross Storage/FS/MM topics, post them too.

Oh, and since we're not the most organised bunch, if you posted a topic
and don't see it in the list, please resend ... we probably lost it in
an email shuffle.

Current Filesystem Topics:

Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
Anshul Madan	reflink for NFS
Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
James Lentini	reflink for NFS
Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
Michael Rubin	Writeback scaling
Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
Al Viro	Sorting out d_revalidate and other dcache issues
Coly Li		directory/large file scalability
Sorin Faibish	Cache writeback discussion

Current Storage Topics:

Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
Hannes Reinecke	libfc/multipath/error handing
James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
Jeff Moyer	IO scheduler
Joel Becker	SAN management plugin
Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME

Plus some MM summit ones which Nick will summarise.

For the benefit of those who've forgotten here's the original Call for
topics and attendees:

This year we'll hold the Linux Storage and Filesystems summit jointly
with the VM summit on the two days before LinuxCon in Boston (that's
Sunday and Monday) at the Renaissance Hotel:

http://events.linuxfoundation.org/events/linuxcon

We're planning to hold some sessions jointly and split into three tracks
(Filesystems, Storage and VM) for others, so we're encouraging proposals
for discussion that cover areas relevant to all three groups as well as
more specific technical topics.

Suggestions for agenda topics should be sent to

lsf10-pc@lists.linuxfoundation.org

and optionally cc the Linux list which would be most interested in it:

SCSI: linux-scsi@vger.kernel.org
FS: linux-fsdevel@vger.kernel.org (plus relevant fs specific list)
MM: linux-mm@kvack.org

Please tag your subject with [LSF/VM TOPIC] so those of us who're not
very organised can find them easily in our inboxes.  The agenda topics
and attendees will be selected by the programme committee, but the final
agenda will be by formed by consensus of the attendees on the day.

We'll try to cap attendance at around 20 per track to facilitate
discussions although the final numbers will depend on the room sizes
at the venue.

Requests to attend should be sent to:

lsf10-pc@lists.linuxfoundation.org

please summarise what you'll bring to the meeting, and what you'd like
to discuss.  please also tag your email with [ATTEND] so there's less
chance of it getting lost in the large mail pile.

Presentations are allowed to guide discussion, but are strongly
discouraged.  There will be no recording or audio bridge, however
written minutes will be published as in previous years:

2009:
http://lwn.net/Articles/327601/
http://lwn.net/Articles/327740/
http://lwn.net/Articles/328347/

Prior years:
http://www.usenix.org/events/lsf08/tech/lsf08sums.pdf
http://www.usenix.org/publications/login/2007-06/openpdfs/lsf07sums.pdf

If you have feedback on last year's meeting that we can use to improve
this year's, please also send that to:

lsf10-pc@lists.linuxfoundation.org

Thanks,

James Bottomley


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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Nicholas A. Bellinger]

On Wed, 2010-06-16 at 15:50 -0500, James Bottomley wrote:
> Given that we're under two months out, I thought it would be time to
> post a summary of the topics we've collected so far (Nick will post the
> MM summit ones later).  Look this over, and if there's anything missing,
> propose it ... or if you have cross Storage/FS/MM topics, post them too.
> 
> Oh, and since we're not the most organised bunch, if you posted a topic
> and don't see it in the list, please resend ... we probably lost it in
> an email shuffle.
> 
> Current Filesystem Topics:
> 
> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> Anshul Madan	reflink for NFS
> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> James Lentini	reflink for NFS
> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> Michael Rubin	Writeback scaling
> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> Al Viro	Sorting out d_revalidate and other dcache issues
> Coly Li		directory/large file scalability
> Sorin Faibish	Cache writeback discussion
> 
> Current Storage Topics:
> 
> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> Hannes Reinecke	libfc/multipath/error handing
> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> Jeff Moyer	IO scheduler
> Joel Becker	SAN management plugin
> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> 
> Plus some MM summit ones which Nick will summarise.
> 

Greeting James and co,

I noticed that the bit wrt to the kernel level target mode fabric
independent configfs infrastructure is not mentioned in the above..

http://marc.info/?l=linux-scsi&m=127010303618447&w=2

Where would this best fit in..?

"A virtual filesystem driven by userspace syscalls to represent a target
HBA/DEV model on top upstream Linux storage subsystems for fabric
modules using a generic set of configfs struct config_groups to
represent target mode fabric endpoints (WWN+TPG+LUN) designed to allow
each their own set of fabric dependent attributes on top of a generic
kernel infrastructure.

The model is to allow the Linux VFS to handle the TCM core HBA/DEV logic
and both fabric independent and dependent data structure dependencies
between LKMs in order to simplify the conversion of existing and
creation of new target mode fabric code."

Best,

--nab


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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Christof Schmitt]

On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
> Given that we're under two months out, I thought it would be time to
> post a summary of the topics we've collected so far (Nick will post the
> MM summit ones later).  Look this over, and if there's anything missing,
> propose it ... or if you have cross Storage/FS/MM topics, post them too.
> 
> Oh, and since we're not the most organised bunch, if you posted a topic
> and don't see it in the list, please resend ... we probably lost it in
> an email shuffle.
> 
> Current Filesystem Topics:
> 
> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> Anshul Madan	reflink for NFS
> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> James Lentini	reflink for NFS
> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> Michael Rubin	Writeback scaling
> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> Al Viro	Sorting out d_revalidate and other dcache issues
> Coly Li		directory/large file scalability
> Sorin Faibish	Cache writeback discussion
> 
> Current Storage Topics:
> 
> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> Hannes Reinecke	libfc/multipath/error handing
> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> Jeff Moyer	IO scheduler
> Joel Becker	SAN management plugin
> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> 
> Plus some MM summit ones which Nick will summarise.
[...]

What about the topic "Stable pages while IO"?
http://www.spinics.net/lists/linux-scsi/msg44074.html

Was it lost during the e-mail shuffle or will it be part of the MM topics?

Christof

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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[James Bottomley]

On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
> > Given that we're under two months out, I thought it would be time to
> > post a summary of the topics we've collected so far (Nick will post the
> > MM summit ones later).  Look this over, and if there's anything missing,
> > propose it ... or if you have cross Storage/FS/MM topics, post them too.
> > 
> > Oh, and since we're not the most organised bunch, if you posted a topic
> > and don't see it in the list, please resend ... we probably lost it in
> > an email shuffle.
> > 
> > Current Filesystem Topics:
> > 
> > Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> > Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> > Anshul Madan	reflink for NFS
> > Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> > Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> > James Lentini	reflink for NFS
> > Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> > Michael Rubin	Writeback scaling
> > Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> > Al Viro	Sorting out d_revalidate and other dcache issues
> > Coly Li		directory/large file scalability
> > Sorin Faibish	Cache writeback discussion
> > 
> > Current Storage Topics:
> > 
> > Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> > Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> > FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> > Hannes Reinecke	libfc/multipath/error handing
> > James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> > Jeff Moyer	IO scheduler
> > Joel Becker	SAN management plugin
> > Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> > 
> > Plus some MM summit ones which Nick will summarise.
> [...]
> 
> What about the topic "Stable pages while IO"?
> http://www.spinics.net/lists/linux-scsi/msg44074.html
> 
> Was it lost during the e-mail shuffle or will it be part of the MM topics?

It's actually listed under 'dma issues' ... but there's really been no
satisfactory resolution or discussion of how one might be achieved.
Most filesystems rely on modifications to in-flight pages for efficiency
and copying every fs I/O page would be horrendous both for performance
and memory consumption.  Nor has there really been an indication that
it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
The latter generates the checksum late enough that it can just discard
incorrect pages ... the former might need simply to turn off DIF for
everything other than DIRECT IO.

James


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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Boaz Harrosh]

On 06/17/2010 12:07 PM, James Bottomley wrote:
> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
>> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
>>> Given that we're under two months out, I thought it would be time to
>>> post a summary of the topics we've collected so far (Nick will post the
>>> MM summit ones later).  Look this over, and if there's anything missing,
>>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
>>>
>>> Oh, and since we're not the most organised bunch, if you posted a topic
>>> and don't see it in the list, please resend ... we probably lost it in
>>> an email shuffle.
>>>
>>> Current Filesystem Topics:
>>>
>>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
>>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
>>> Anshul Madan	reflink for NFS
>>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
>>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
>>> James Lentini	reflink for NFS
>>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
>>> Michael Rubin	Writeback scaling
>>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
>>> Al Viro	Sorting out d_revalidate and other dcache issues
>>> Coly Li		directory/large file scalability
>>> Sorin Faibish	Cache writeback discussion
>>>
>>> Current Storage Topics:
>>>
>>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
>>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
>>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
>>> Hannes Reinecke	libfc/multipath/error handing
>>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
>>> Jeff Moyer	IO scheduler
>>> Joel Becker	SAN management plugin
>>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
>>>
>>> Plus some MM summit ones which Nick will summarise.
>> [...]
>>
>> What about the topic "Stable pages while IO"?
>> http://www.spinics.net/lists/linux-scsi/msg44074.html
>>
>> Was it lost during the e-mail shuffle or will it be part of the MM topics?
> 
> It's actually listed under 'dma issues' ... but there's really been no
> satisfactory resolution or discussion of how one might be achieved.
> Most filesystems rely on modifications to in-flight pages for efficiency
> and copying every fs I/O page would be horrendous both for performance
> and memory consumption.  Nor has there really been an indication that
> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
> The latter generates the checksum late enough that it can just discard
> incorrect pages ... the former might need simply to turn off DIF for
> everything other than DIRECT IO.

What about raid and mirror that do copy the complete IO load
just because of that? They gave up long ago but wouldn't they
gain if that was revisited? (And so would DIF/checksum)

> 
> James
> 

Boaz

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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Vladislav Bolkhovitin]

James Bottomley, on 06/17/2010 08:07 PM wrote:
> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
>> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
>>> Given that we're under two months out, I thought it would be time to
>>> post a summary of the topics we've collected so far (Nick will post the
>>> MM summit ones later).  Look this over, and if there's anything missing,
>>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
>>>
>>> Oh, and since we're not the most organised bunch, if you posted a topic
>>> and don't see it in the list, please resend ... we probably lost it in
>>> an email shuffle.
>>>
>>> Current Filesystem Topics:
>>>
>>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
>>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
>>> Anshul Madan	reflink for NFS
>>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
>>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
>>> James Lentini	reflink for NFS
>>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
>>> Michael Rubin	Writeback scaling
>>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
>>> Al Viro	Sorting out d_revalidate and other dcache issues
>>> Coly Li		directory/large file scalability
>>> Sorin Faibish	Cache writeback discussion
>>>
>>> Current Storage Topics:
>>>
>>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
>>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
>>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
>>> Hannes Reinecke	libfc/multipath/error handing
>>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
>>> Jeff Moyer	IO scheduler
>>> Joel Becker	SAN management plugin
>>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
>>>
>>> Plus some MM summit ones which Nick will summarise.
>> [...]
>>
>> What about the topic "Stable pages while IO"?
>> http://www.spinics.net/lists/linux-scsi/msg44074.html
>>
>> Was it lost during the e-mail shuffle or will it be part of the MM topics?
> 
> It's actually listed under 'dma issues' ... but there's really been no
> satisfactory resolution or discussion of how one might be achieved.
> Most filesystems rely on modifications to in-flight pages for efficiency
> and copying every fs I/O page would be horrendous both for performance
> and memory consumption.  Nor has there really been an indication that
> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.

You forgot the third: advanced storage, including MPIO clusters, where 
retry of the write of the modified in-flight pages while the original 
write for them not yet completed might cause out of the expected order 
execution of the writes and data corruption (old data written instead of 
new).

Vlad

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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[James Bottomley]

On Thu, 2010-06-17 at 20:34 +0400, Vladislav Bolkhovitin wrote:
> James Bottomley, on 06/17/2010 08:07 PM wrote:
> > On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
> >> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
> >>> Given that we're under two months out, I thought it would be time to
> >>> post a summary of the topics we've collected so far (Nick will post the
> >>> MM summit ones later).  Look this over, and if there's anything missing,
> >>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
> >>>
> >>> Oh, and since we're not the most organised bunch, if you posted a topic
> >>> and don't see it in the list, please resend ... we probably lost it in
> >>> an email shuffle.
> >>>
> >>> Current Filesystem Topics:
> >>>
> >>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> >>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> >>> Anshul Madan	reflink for NFS
> >>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> >>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> >>> James Lentini	reflink for NFS
> >>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> >>> Michael Rubin	Writeback scaling
> >>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> >>> Al Viro	Sorting out d_revalidate and other dcache issues
> >>> Coly Li		directory/large file scalability
> >>> Sorin Faibish	Cache writeback discussion
> >>>
> >>> Current Storage Topics:
> >>>
> >>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> >>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> >>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> >>> Hannes Reinecke	libfc/multipath/error handing
> >>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> >>> Jeff Moyer	IO scheduler
> >>> Joel Becker	SAN management plugin
> >>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> >>>
> >>> Plus some MM summit ones which Nick will summarise.
> >> [...]
> >>
> >> What about the topic "Stable pages while IO"?
> >> http://www.spinics.net/lists/linux-scsi/msg44074.html
> >>
> >> Was it lost during the e-mail shuffle or will it be part of the MM topics?
> > 
> > It's actually listed under 'dma issues' ... but there's really been no
> > satisfactory resolution or discussion of how one might be achieved.
> > Most filesystems rely on modifications to in-flight pages for efficiency
> > and copying every fs I/O page would be horrendous both for performance
> > and memory consumption.  Nor has there really been an indication that
> > it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
> 
> You forgot the third: advanced storage, including MPIO clusters, where 
> retry of the write of the modified in-flight pages while the original 
> write for them not yet completed might cause out of the expected order 
> execution of the writes and data corruption (old data written instead of 
> new).

I don't think that's a problem. Multiple commands in flight to the same
I/O region can get reordered because we only use simple tagging
regardless of advanced or otherwise storage.  The VM seems to wait for
one write to complete before starting another because of the way the
flush threads work.

James


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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Vladislav Bolkhovitin]

James Bottomley, on 06/17/2010 08:42 PM wrote:
> On Thu, 2010-06-17 at 20:34 +0400, Vladislav Bolkhovitin wrote:
>> James Bottomley, on 06/17/2010 08:07 PM wrote:
>>> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
>>>> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
>>>>> Given that we're under two months out, I thought it would be time to
>>>>> post a summary of the topics we've collected so far (Nick will post the
>>>>> MM summit ones later).  Look this over, and if there's anything missing,
>>>>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
>>>>>
>>>>> Oh, and since we're not the most organised bunch, if you posted a topic
>>>>> and don't see it in the list, please resend ... we probably lost it in
>>>>> an email shuffle.
>>>>>
>>>>> Current Filesystem Topics:
>>>>>
>>>>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
>>>>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
>>>>> Anshul Madan	reflink for NFS
>>>>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
>>>>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
>>>>> James Lentini	reflink for NFS
>>>>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
>>>>> Michael Rubin	Writeback scaling
>>>>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
>>>>> Al Viro	Sorting out d_revalidate and other dcache issues
>>>>> Coly Li		directory/large file scalability
>>>>> Sorin Faibish	Cache writeback discussion
>>>>>
>>>>> Current Storage Topics:
>>>>>
>>>>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
>>>>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
>>>>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
>>>>> Hannes Reinecke	libfc/multipath/error handing
>>>>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
>>>>> Jeff Moyer	IO scheduler
>>>>> Joel Becker	SAN management plugin
>>>>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
>>>>>
>>>>> Plus some MM summit ones which Nick will summarise.
>>>> [...]
>>>>
>>>> What about the topic "Stable pages while IO"?
>>>> http://www.spinics.net/lists/linux-scsi/msg44074.html
>>>>
>>>> Was it lost during the e-mail shuffle or will it be part of the MM topics?
>>> It's actually listed under 'dma issues' ... but there's really been no
>>> satisfactory resolution or discussion of how one might be achieved.
>>> Most filesystems rely on modifications to in-flight pages for efficiency
>>> and copying every fs I/O page would be horrendous both for performance
>>> and memory consumption.  Nor has there really been an indication that
>>> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
>> You forgot the third: advanced storage, including MPIO clusters, where 
>> retry of the write of the modified in-flight pages while the original 
>> write for them not yet completed might cause out of the expected order 
>> execution of the writes and data corruption (old data written instead of 
>> new).
> 
> I don't think that's a problem. Multiple commands in flight to the same
> I/O region can get reordered because we only use simple tagging
> regardless of advanced or otherwise storage. The VM seems to wait for
> one write to complete before starting another because of the way the
> flush threads work.

I hope so, but: (1) we can see such writes (see 
http://lists.linbit.com/pipermail/drbd-user/2009-April/011891.html, for 
instance) and (2) Boaz said it's possible. From the "seems" you wrote 
looks like your are also not too sure. So, if it isn't possible, it 
would be good if someone familar with VM internals confirmed this.

Gennadiy,

If possible, can you recheck in your setup with a real Linux as 
initiator to confirm if Linux is suffers from the concurrent writes 
you've seen or not, please?

Vlad

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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[James Bottomley]

On Thu, 2010-06-17 at 21:11 +0400, Vladislav Bolkhovitin wrote:
> James Bottomley, on 06/17/2010 08:42 PM wrote:
> > On Thu, 2010-06-17 at 20:34 +0400, Vladislav Bolkhovitin wrote:
> >> James Bottomley, on 06/17/2010 08:07 PM wrote:
> >>> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
> >>>> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
> >>>>> Given that we're under two months out, I thought it would be time to
> >>>>> post a summary of the topics we've collected so far (Nick will post the
> >>>>> MM summit ones later).  Look this over, and if there's anything missing,
> >>>>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
> >>>>>
> >>>>> Oh, and since we're not the most organised bunch, if you posted a topic
> >>>>> and don't see it in the list, please resend ... we probably lost it in
> >>>>> an email shuffle.
> >>>>>
> >>>>> Current Filesystem Topics:
> >>>>>
> >>>>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> >>>>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> >>>>> Anshul Madan	reflink for NFS
> >>>>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> >>>>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> >>>>> James Lentini	reflink for NFS
> >>>>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> >>>>> Michael Rubin	Writeback scaling
> >>>>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> >>>>> Al Viro	Sorting out d_revalidate and other dcache issues
> >>>>> Coly Li		directory/large file scalability
> >>>>> Sorin Faibish	Cache writeback discussion
> >>>>>
> >>>>> Current Storage Topics:
> >>>>>
> >>>>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> >>>>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> >>>>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> >>>>> Hannes Reinecke	libfc/multipath/error handing
> >>>>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> >>>>> Jeff Moyer	IO scheduler
> >>>>> Joel Becker	SAN management plugin
> >>>>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> >>>>>
> >>>>> Plus some MM summit ones which Nick will summarise.
> >>>> [...]
> >>>>
> >>>> What about the topic "Stable pages while IO"?
> >>>> http://www.spinics.net/lists/linux-scsi/msg44074.html
> >>>>
> >>>> Was it lost during the e-mail shuffle or will it be part of the MM topics?
> >>> It's actually listed under 'dma issues' ... but there's really been no
> >>> satisfactory resolution or discussion of how one might be achieved.
> >>> Most filesystems rely on modifications to in-flight pages for efficiency
> >>> and copying every fs I/O page would be horrendous both for performance
> >>> and memory consumption.  Nor has there really been an indication that
> >>> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
> >> You forgot the third: advanced storage, including MPIO clusters, where 
> >> retry of the write of the modified in-flight pages while the original 
> >> write for them not yet completed might cause out of the expected order 
> >> execution of the writes and data corruption (old data written instead of 
> >> new).
> > 
> > I don't think that's a problem. Multiple commands in flight to the same
> > I/O region can get reordered because we only use simple tagging
> > regardless of advanced or otherwise storage. The VM seems to wait for
> > one write to complete before starting another because of the way the
> > flush threads work.
> 
> I hope so, but: (1) we can see such writes (see 
> http://lists.linbit.com/pipermail/drbd-user/2009-April/011891.html, for 
> instance)

So the email says blockio mode ... which I take it isn't through the
pagecache cleaning?  All bets are off if the user initiates the
writeback ... and certainly you can get two blocks in flight for the
same destination using DIRECT IO ... but that's up to the applications
to fix ... we don't guarantee ordering in that case.

James


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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Vladislav Bolkhovitin]

James Bottomley, on 06/17/2010 09:37 PM wrote:
> On Thu, 2010-06-17 at 21:11 +0400, Vladislav Bolkhovitin wrote:
>> James Bottomley, on 06/17/2010 08:42 PM wrote:
>>> On Thu, 2010-06-17 at 20:34 +0400, Vladislav Bolkhovitin wrote:
>>>> James Bottomley, on 06/17/2010 08:07 PM wrote:
>>>>> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
>>>>>> On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
>>>>>>> Given that we're under two months out, I thought it would be time to
>>>>>>> post a summary of the topics we've collected so far (Nick will post the
>>>>>>> MM summit ones later).  Look this over, and if there's anything missing,
>>>>>>> propose it ... or if you have cross Storage/FS/MM topics, post them too.
>>>>>>>
>>>>>>> Oh, and since we're not the most organised bunch, if you posted a topic
>>>>>>> and don't see it in the list, please resend ... we probably lost it in
>>>>>>> an email shuffle.
>>>>>>>
>>>>>>> Current Filesystem Topics:
>>>>>>>
>>>>>>> Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
>>>>>>> Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
>>>>>>> Anshul Madan	reflink for NFS
>>>>>>> Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
>>>>>>> Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
>>>>>>> James Lentini	reflink for NFS
>>>>>>> Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
>>>>>>> Michael Rubin	Writeback scaling
>>>>>>> Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
>>>>>>> Al Viro	Sorting out d_revalidate and other dcache issues
>>>>>>> Coly Li		directory/large file scalability
>>>>>>> Sorin Faibish	Cache writeback discussion
>>>>>>>
>>>>>>> Current Storage Topics:
>>>>>>>
>>>>>>> Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
>>>>>>> Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
>>>>>>> FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
>>>>>>> Hannes Reinecke	libfc/multipath/error handing
>>>>>>> James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
>>>>>>> Jeff Moyer	IO scheduler
>>>>>>> Joel Becker	SAN management plugin
>>>>>>> Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
>>>>>>>
>>>>>>> Plus some MM summit ones which Nick will summarise.
>>>>>> [...]
>>>>>>
>>>>>> What about the topic "Stable pages while IO"?
>>>>>> http://www.spinics.net/lists/linux-scsi/msg44074.html
>>>>>>
>>>>>> Was it lost during the e-mail shuffle or will it be part of the MM topics?
>>>>> It's actually listed under 'dma issues' ... but there's really been no
>>>>> satisfactory resolution or discussion of how one might be achieved.
>>>>> Most filesystems rely on modifications to in-flight pages for efficiency
>>>>> and copying every fs I/O page would be horrendous both for performance
>>>>> and memory consumption.  Nor has there really been an indication that
>>>>> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
>>>> You forgot the third: advanced storage, including MPIO clusters, where 
>>>> retry of the write of the modified in-flight pages while the original 
>>>> write for them not yet completed might cause out of the expected order 
>>>> execution of the writes and data corruption (old data written instead of 
>>>> new).
>>> I don't think that's a problem. Multiple commands in flight to the same
>>> I/O region can get reordered because we only use simple tagging
>>> regardless of advanced or otherwise storage. The VM seems to wait for
>>> one write to complete before starting another because of the way the
>>> flush threads work.
>> I hope so, but: (1) we can see such writes (see 
>> http://lists.linbit.com/pipermail/drbd-user/2009-April/011891.html, for 
>> instance)
> 
> So the email says blockio mode ... which I take it isn't through the
> pagecache cleaning?  All bets are off if the user initiates the
> writeback ... and certainly you can get two blocks in flight for the
> same destination using DIRECT IO ... but that's up to the applications
> to fix ... we don't guarantee ordering in that case.

That's blockio on the target. The target stack just passed down to its 
backstorage incoming from the initiator SCSI commands as a block 
requests in 1:1 mapping. But the SCSI commands were sent by the 
initiator. So, the concurrent writes came from the initiator.

Gennadiy,

Which application did you use on the initiator to generate load when you 
had the concurrent writes?

Vlad

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Re: Current topics for LSF10/MM Summit 8-9 August in Boston

[Christof Schmitt]

On Thu, Jun 17, 2010 at 11:07:30AM -0500, James Bottomley wrote:
> On Thu, 2010-06-17 at 18:00 +0200, Christof Schmitt wrote:
> > On Wed, Jun 16, 2010 at 03:50:59PM -0500, James Bottomley wrote:
> > > Given that we're under two months out, I thought it would be time to
> > > post a summary of the topics we've collected so far (Nick will post the
> > > MM summit ones later).  Look this over, and if there's anything missing,
> > > propose it ... or if you have cross Storage/FS/MM topics, post them too.
> > > 
> > > Oh, and since we're not the most organised bunch, if you posted a topic
> > > and don't see it in the list, please resend ... we probably lost it in
> > > an email shuffle.
> > > 
> > > Current Filesystem Topics:
> > > 
> > > Alex Elder	Upstream maintainer for XFS, general discussion on FS/IO
> > > Aneesh Kumar	Rich-acl patches which work better with NFSv4 acl and CIFS acl
> > > Anshul Madan	reflink for NFS
> > > Chuck Lever	NFS/IPV6 and NFS O_DIRECT, Wu's read-ahead work, vitro perf tools
> > > Eric Sandeen	Advances in testing, TRIM/DISCARD/Alignment, writeback sanity
> > > James Lentini	reflink for NFS
> > > Jan Kara	Discuss/drive sanity review of writeback and general ext*/jbd 
> > > Michael Rubin	Writeback scaling
> > > Sage Weil	Statlite, generic interface for describing file striping for distributed FS, VFS scalability
> > > Al Viro	Sorting out d_revalidate and other dcache issues
> > > Coly Li		directory/large file scalability
> > > Sorin Faibish	Cache writeback discussion
> > > 
> > > Current Storage Topics:
> > > 
> > > Eric Seppanen	Next generation SSDs, performance implications on Linux I/O
> > > Boaz Harrosh	PNFS performance considerations, bio_list based/async raidN for generic use; stable pages for I/O
> > > FUJITA Tomonori	SCSI target mode, iSCSI, block layer SG (bsg), sg, IOMMU, DMA issues
> > > Hannes Reinecke	libfc/multipath/error handing
> > > James Smart	FCOE proposal for rework of the FC sysfs tree, work with Hannes on other transport/SCSI subsystem topics
> > > Jeff Moyer	IO scheduler
> > > Joel Becker	SAN management plugin
> > > Martin Petersen	Updates on DIF/DIX, TRIM/DISCARD/UNMAP, generic support for WRITE_SAME
> > > 
> > > Plus some MM summit ones which Nick will summarise.
> > [...]
> > 
> > What about the topic "Stable pages while IO"?
> > http://www.spinics.net/lists/linux-scsi/msg44074.html
> > 
> > Was it lost during the e-mail shuffle or will it be part of the MM topics?
> 
> It's actually listed under 'dma issues' ... but there's really been no
> satisfactory resolution or discussion of how one might be achieved.
> Most filesystems rely on modifications to in-flight pages for efficiency
> and copying every fs I/O page would be horrendous both for performance
> and memory consumption.  Nor has there really been an indication that
> it's a serious issue.  The two sufferers are DIF and iSCSI checksum.
> The latter generates the checksum late enough that it can just discard
> incorrect pages ... the former might need simply to turn off DIF for
> everything other than DIRECT IO.

It is a serious problem when using DIF, so turning off this feature or
only using XFS and direct i/o does not sound very satisfying. But then
i also see the points that have been discussed and that there is no
simple solution.

Christof

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