This is a note to let you know that I've just added the patch titled
mm/filemap.c: avoid always dirtying mapping->flags on O_DIRECT
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-filemap.c-avoid-always-dirtying-mapping-flags-on-o_direct.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7fcbbaf18392f0b17c95e2f033c8ccf87eecde1d Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxx>
Date: Thu, 22 May 2014 11:54:16 -0700
Subject: mm/filemap.c: avoid always dirtying mapping->flags on O_DIRECT
From: Jens Axboe <axboe@xxxxxx>
commit 7fcbbaf18392f0b17c95e2f033c8ccf87eecde1d upstream.
In some testing I ran today (some fio jobs that spread over two nodes),
we end up spending 40% of the time in filemap_check_errors(). That
smells fishy. Looking further, this is basically what happens:
blkdev_aio_read()
generic_file_aio_read()
filemap_write_and_wait_range()
if (!mapping->nr_pages)
filemap_check_errors()
and filemap_check_errors() always attempts two test_and_clear_bit() on
the mapping flags, thus dirtying it for every single invocation. The
patch below tests each of these bits before clearing them, avoiding this
issue. In my test case (4-socket box), performance went from 1.7M IOPS
to 4.0M IOPS.
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -192,9 +192,11 @@ static int filemap_check_errors(struct a
{
int ret = 0;
/* Check for outstanding write errors */
- if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
+ if (test_bit(AS_ENOSPC, &mapping->flags) &&
+ test_and_clear_bit(AS_ENOSPC, &mapping->flags))
ret = -ENOSPC;
- if (test_and_clear_bit(AS_EIO, &mapping->flags))
+ if (test_bit(AS_EIO, &mapping->flags) &&
+ test_and_clear_bit(AS_EIO, &mapping->flags))
ret = -EIO;
return ret;
}
Patches currently in stable-queue which might be from axboe@xxxxxx are
queue-3.14/mm-filemap.c-avoid-always-dirtying-mapping-flags-on-o_direct.patch
queue-3.14/drbd-fix-regression-out-of-mem-failed-to-invoke-fence-peer-helper.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html