This patch looks like it should be in the 3.11-stable tree, should we apply it?
------------------ From: "Jan Kara <[email protected]>" commit 9c12a831d73dd938a22418d70b39aed4feb4bdf2 upstream The Linux Kernel Performance project guys have reported that commit 4e7ea81db5 introduces a performance regression for the following fio workload: [global] direct=0 ioengine=mmap size=1500M bs=4k pre_read=1 numjobs=1 overwrite=1 loops=5 runtime=300 group_reporting invalidate=0 directory=/mnt/ file_service_type=random:36 file_service_type=random:36 [job0] startdelay=0 rw=randrw filename=data0/f1:data0/f2 [job1] startdelay=0 rw=randrw filename=data0/f2:data0/f1 ... [job7] startdelay=0 rw=randrw filename=data0/f2:data0/f1 The culprit of the problem is that after the commit ext4_writepages() are more aggressive in writing back pages. Thus we have less consecutive dirty pages resulting in more seeking. This increased aggressivity is caused by a bug in the condition terminating ext4_writepages(). We start writing from the beginning of the file even if we should have terminated ext4_writepages() because wbc->nr_to_write <= 0. After fixing the condition the throughput of the fio workload is about 20% better than before writeback reorganization. Reported-by: "Yan, Zheng" <[email protected]> Signed-off-by: Jan Kara <[email protected]> Signed-off-by: "Theodore Ts'o" <[email protected]> Signed-off-by: Jonghwan Choi <[email protected]> --- fs/ext4/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index ea4d188..f2ab232 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2560,7 +2560,7 @@ retry: break; } blk_finish_plug(&plug); - if (!ret && !cycled) { + if (!ret && !cycled && wbc->nr_to_write > 0) { cycled = 1; mpd.last_page = writeback_index - 1; mpd.first_page = 0; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
