Patch "jbd2: fix dbench4 performance regression for 'nobarrier' mounts" has been added to the 4.10-stable tree
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This is a note to let you know that I've just added the patch titled
jbd2: fix dbench4 performance regression for 'nobarrier' mounts
to the 4.10-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:
jbd2-fix-dbench4-performance-regression-for-nobarrier-mounts.patch
and it can be found in the queue-4.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
5052b069acf73866d00077d8bc49983c3ee903e5Mon Sep 17 00:00:00 2001
From: Jan Kara <[email protected]>
Date: Sat, 29 Apr 2017 21:07:30 -0400
Subject: jbd2: fix dbench4 performance regression for 'nobarrier' mounts
From: Jan Kara <[email protected]>
commit 5052b069acf73866d00077d8bc49983c3ee903e5 upstream.
Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as synchronous" removed REQ_SYNC flag from WRITE_FUA implementation. Since JBD2 strips REQ_FUA and REQ_FLUSH flags from submitted IO when the filesystem is mounted with nobarrier mount option, journal superblock writes ended up being async writes after this patch and that caused heavy performance regression for dbench4 benchmark with high number of processes. In my test setup with HP RAID array with non-volatile write cache and 32 GB ram, dbench4 runs with 8 processes regressed by ~25%.
Fix the problem by making sure journal superblock writes are always treated as synchronous since they generally block progress of the journalling machinery and thus the whole filesystem.
--- fs/jbd2/journal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
fs/jbd2/journal.c +1 -1
@@ -1348,7 +1348,7 @@ static int jbd2_write_superblock(journaljbd2_superblock_csum_set (journal, sb);get_bh (bh); bh->b_end_io = end_buffer_write_sync; - ret =submit_bh (REQ_OP_WRITE , write_flags, bh); + ret =submit_bh (REQ_OP_WRITE , write_flags |REQ_SYNC , bh);wait_on_buffer (bh);if (buffer_write_io_error (bh)) {clear_buffer_write_io_error (bh);
Patches currently in stable-queue which might be from [email protected] are
queue-4.10/fs-block_dev-always-invalidate-cleancache-in-invalidate_bdev.patch queue-4.10/jbd2-fix-dbench4-performance-regression-for-nobarrier-mounts.patch