From: Jeremy Sanders <jeremy@jeremysanders.net>
To: linux-btrfs@vger.kernel.org
Subject: Btrfs switches to using mostly one thread
Date: Thu, 08 Dec 2011 15:19:38 +0000 [thread overview]
Message-ID: <jbqkib$v1g$1@dough.gmane.org> (raw)
Hi - I'm trying out btrfs again, and I see the same old bug in kernel 3.1.4
(Fedora 16, x86_64, dual-core), where after a few hours of writing, it
switches from writing with several threads to writing with one:
After:
21996 root 20 0 0 0 0 R 97.2 0.0 109:03.57 btrfs-delalloc-
23332 root 20 0 137m 14m 1000 S 3.3 1.0 5:40.32 tar
23333 root 20 0 125m 3620 960 D 2.7 0.2 4:33.04 tar
22026 root 20 0 0 0 0 S 2.0 0.0 3:14.73 btrfs-endio-wri
23626 root 20 0 0 0 0 S 2.0 0.0 0:17.64 kworker/0:0
55 root 20 0 0 0 0 S 1.3 0.0 6:46.35 kswapd0
22255 root 20 0 0 0 0 S 1.0 0.0 2:12.30 kworker/0:2
22025 root 20 0 0 0 0 S 0.3 0.0 3:16.34 btrfs-endio-wri
Before:
23867 root 20 0 0 0 0 R 66.6 0.0 0:13.45 btrfs-delalloc-
24021 root 20 0 0 0 0 R 60.6 0.0 0:10.58 btrfs-delalloc-
24025 root 20 0 0 0 0 R 45.7 0.0 0:10.01 btrfs-delalloc-
24018 root 20 0 124m 2384 1116 R 8.6 0.2 0:03.31 tar
24019 root 20 0 124m 2276 1052 S 7.0 0.1 0:02.47 tar
55 root 20 0 0 0 0 S 2.6 0.0 6:47.92 kswapd0
24022 root 20 0 0 0 0 S 2.0 0.0 0:00.59 btrfs-endio-wri
22255 root 20 0 0 0 0 S 1.7 0.0 2:13.45 kworker/0:2
23626 root 20 0 0 0 0 S 1.7 0.0 0:18.84 kworker/0:0
24024 root 20 0 0 0 0 S 1.7 0.0 0:00.77 btrfs-endio-wri
23866 root 20 0 0 0 0 S 0.7 0.0 0:00.25 btrfs-submit-0
23912 root 20 0 0 0 0 D 0.3 0.0 0:00.26 flush-btrfs-4
It can be put back to its initial behaviour by unmounting and reloading the
btrfs kernel module. I'm using compress-force=zlib for this, and it's
writing with a tar-to-tar pipe (or rsync). I think switching to one thread
it has a pretty negative impact on write speed (50%).
I think the cause is writing lots of small files to the disk, but I can't be
sure.
Jeremy
next reply other threads:[~2011-12-08 15:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-08 15:19 Jeremy Sanders [this message]
2011-12-08 15:32 ` Btrfs switches to using mostly one thread Chris Mason
2011-12-08 15:36 ` Jeremy Sanders
2011-12-08 16:57 ` Jeremy Sanders
2011-12-08 17:23 ` Chris Mason
2011-12-08 17:39 ` Jeremy Sanders
2011-12-08 20:11 ` Chris Mason
2011-12-09 12:05 ` Jeremy Sanders
2011-12-09 14:18 ` Chris Mason
2011-12-09 14:22 ` Jeremy Sanders
2011-12-09 12:15 ` Arne Jansen
2011-12-09 12:20 ` Jeremy Sanders
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