Subject: [merged] mm-filemapc-avoid-always-dirtying-mapping-flags-on-o_direct.patch removed from -mm tree To: axboe@xxxxxx,jmoyer@xxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Tue, 27 May 2014 13:22:15 -0700 The patch titled Subject: mm/filemap.c: avoid always dirtying mapping->flags on O_DIRECT has been removed from the -mm tree. Its filename was mm-filemapc-avoid-always-dirtying-mapping-flags-on-o_direct.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Jens Axboe <axboe@xxxxxx> Subject: 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@xxxxxx> Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff -puN mm/filemap.c~mm-filemapc-avoid-always-dirtying-mapping-flags-on-o_direct mm/filemap.c --- a/mm/filemap.c~mm-filemapc-avoid-always-dirtying-mapping-flags-on-o_direct +++ a/mm/filemap.c @@ -257,9 +257,11 @@ 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 -mm which might be from axboe@xxxxxx are linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html