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| author | Jens Axboe <axboe@fb.com> | 2014-05-22 11:54:16 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-10-09 12:21:29 -0700 |
| commit | 6591981a30a8c752b1c537211f7fe4b9530fea41 (patch) | |
| tree | 01ae6e14bec1832a0eabb14b838b79b3937ee7b7 /mm | |
| parent | 29c2a88157819d1e68ffea8b7d80117b332c8efe (diff) | |
| download | lwn-6591981a30a8c752b1c537211f7fe4b9530fea41.tar.gz lwn-6591981a30a8c752b1c537211f7fe4b9530fea41.zip | |
mm/filemap.c: avoid always dirtying mapping->flags on O_DIRECT
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@fb.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/filemap.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 068cd2a63d32..c2cc7c95eff1 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -192,9 +192,11 @@ static int filemap_check_errors(struct address_space *mapping) { 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; } |