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authorJens Axboe <axboe@fb.com>2014-05-22 11:54:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-05-23 09:37:29 -0700
commit7fcbbaf18392f0b17c95e2f033c8ccf87eecde1d (patch)
treeeef8e5449c79bf596cf16bca47de1c8ca60048d0 /mm/madvise.c
parentb985194c8c0a130ed155b71662e39f7eaea4876f (diff)
mm/filemap.c: avoid always dirtying mapping->flags on O_DIRECT
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>
Diffstat (limited to 'mm/madvise.c')
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