[PATCH 1/2] NFS: call block plug around direct write

[PATCH 1/2] NFS: call block plug around direct write

[Peng Tao]

We bypass generic_file_aio_write() but would want to call block plug.

Signed-off-by: Peng Tao <tao.peng@emc.com>
---
 fs/nfs/direct.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index a1b81dd..a485560 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -46,6 +46,7 @@
 #include <linux/kref.h>
 #include <linux/slab.h>
 #include <linux/task_io_accounting_ops.h>
+#include <linux/blkdev.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
@@ -922,6 +923,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
 	struct file *file = iocb->ki_filp;
 	struct address_space *mapping = file->f_mapping;
 	size_t count;
+	struct blk_plug plug;
 
 	count = iov_length(iov, nr_segs);
 	nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
@@ -948,7 +950,9 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
 
 	task_io_account_write(count);
 
+	blk_start_plug(&plug);
 	retval = nfs_direct_write(iocb, iov, nr_segs, pos, count);
+	blk_finish_plug(&plug);
 	if (retval > 0) {
 		struct inode *inode = mapping->host;
 
-- 
1.7.1.262.g5ef3d

[PATCH 2/2] NFS: call block plug around direct read

[Peng Tao]

Signed-off-by: Peng Tao <tao.peng@emc.com>
---
 fs/nfs/direct.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index a485560..2cf3b45 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -866,6 +866,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
 	ssize_t retval = -EINVAL;
 	struct file *file = iocb->ki_filp;
 	struct address_space *mapping = file->f_mapping;
+	struct blk_plug plug;
 	size_t count;
 
 	count = iov_length(iov, nr_segs);
@@ -886,7 +887,9 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
 
 	task_io_account_read(count);
 
+	blk_start_plug(&plug);
 	retval = nfs_direct_read(iocb, iov, nr_segs, pos);
+	blk_finish_plug(&plug);
 	if (retval > 0)
 		iocb->ki_pos = pos + retval;
 
-- 
1.7.1.262.g5ef3d

Re: [PATCH 2/2] NFS: call block plug around direct read

[Myklebust, Trond]

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dGFwcC5jb20NCg0K

Re: [PATCH 1/2] NFS: call block plug around direct write

[Christoph Hellwig]

On Tue, May 15, 2012 at 11:38:22PM +0800, Peng Tao wrote:
> We bypass generic_file_aio_write() but would want to call block plug.

We in this case is the pnfs block driver at most.  Thus these should
be pnfs block code.

Re: [PATCH 1/2] NFS: call block plug around direct write

[Boaz Harrosh]

On 05/15/2012 07:08 PM, Christoph Hellwig wrote:

> On Tue, May 15, 2012 at 11:38:22PM +0800, Peng Tao wrote:
>> We bypass generic_file_aio_write() but would want to call block plug.
> 
> We in this case is the pnfs block driver at most.  Thus these should
> be pnfs block code.
> 
> --
> 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


I thought so too.

But reading the code more closely it might be hard for the blocklayout
to figure out the right state to call these two. Specially the call to
blk_finish_plug(). So you might need to add a new LD API such as
LD()->finish_plug() which is empty for others.

But again inspecting the code it looks like blk_start_plug() is a no-op
and blk_finish_plug() is specially optimized for the empty case.

So is it worth it, the extra effort? I do understand the temptation
to get lazy here.

Just my $0.017
Boaz

Re: [PATCH 1/2] NFS: call block plug around direct write

[Peng Tao]

On Wed, May 16, 2012 at 12:23 AM, Boaz Harrosh <bharrosh@panasas.com> wrote:
> On 05/15/2012 07:08 PM, Christoph Hellwig wrote:
>
>> On Tue, May 15, 2012 at 11:38:22PM +0800, Peng Tao wrote:
>>> We bypass generic_file_aio_write() but would want to call block plug.
>>
>> We in this case is the pnfs block driver at most.  Thus these should
>> be pnfs block code.
Agreed. Just that for buffer IO case all call into block plug, so I
thought it might be OK in DIO case as well... Anyway. I will make it
block specific and call it LD()->dio_begin and LD()->dio_end. I am
cooking some dio alignment patches for block layout driver and would
love to put them there as well.

>>
>> --
>> 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
>
>
> I thought so too.
>
> But reading the code more closely it might be hard for the blocklayout
> to figure out the right state to call these two. Specially the call to
> blk_finish_plug(). So you might need to add a new LD API such as
> LD()->finish_plug() which is empty for others.
>
> But again inspecting the code it looks like blk_start_plug() is a no-op
> and blk_finish_plug() is specially optimized for the empty case.
>
They are empty only when !CONFIG_BLOCK. I will make it block layout
specific as said above.

Thanks,
Tao
> So is it worth it, the extra effort? I do understand the temptation
> to get lazy here.
>
> Just my $0.017
> Boaz

Re: [PATCH 1/2] NFS: call block plug around direct write

[Boaz Harrosh]

On 05/16/2012 03:35 AM, Peng Tao wrote:

> On Wed, May 16, 2012 at 12:23 AM, Boaz Harrosh <bharrosh@panasas.com> wrote:
>> On 05/15/2012 07:08 PM, Christoph Hellwig wrote:
>>
>>> On Tue, May 15, 2012 at 11:38:22PM +0800, Peng Tao wrote:
>>>> We bypass generic_file_aio_write() but would want to call block plug.
>>>
>>> We in this case is the pnfs block driver at most.  Thus these should
>>> be pnfs block code.
> Agreed. Just that for buffer IO case all call into block plug, so I
> thought it might be OK in DIO case as well... Anyway. I will make it
> block specific and call it LD()->dio_begin and LD()->dio_end. I am
> cooking some dio alignment patches for block layout driver and would
> love to put them there as well.
> 
>>>
>>> --
>>> 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
>>
>>
>> I thought so too.
>>
>> But reading the code more closely it might be hard for the blocklayout
>> to figure out the right state to call these two. Specially the call to
>> blk_finish_plug(). So you might need to add a new LD API such as
>> LD()->finish_plug() which is empty for others.
>>
>> But again inspecting the code it looks like blk_start_plug() is a no-op
>> and blk_finish_plug() is specially optimized for the empty case.
>>
> They are empty only when !CONFIG_BLOCK. I will make it block layout
> specific as said above.
> 


You miss understood. At the very top of blk_finish_plug() there
is an if (list_empty()) return. So if there was no activity between
plug/unplug the function is very fast.

But your above plan for alignment+plug sounds very good.

Thanks
Boaz

> Thanks,
> Tao
>> So is it worth it, the extra effort? I do understand the temptation
>> to get lazy here.
>>
>> Just my $0.017
>> Boaz

Re: [PATCH 1/2] NFS: call block plug around direct write

[Myklebust, Trond]

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