On Tue, 21 Jun 2011 11:24:11 -0400, Calvin Walton wrote:
On Mon, 2011-06-20 at 23:51 +0200, Henning Rohlfs wrote:
Hello,
I've migrated my system to btrfs (raid1) a few months ago. Since
then
the performance has been pretty bad, but recently it's gotten
unbearable: a simple sync called while the system is idle can take
20 up
to 60 seconds. Creating or deleting files often has several seconds
latency, too.
I think I’ve been seeing a fairly similar, or possibly the same?
issue
as well. It looks like it’s actually a regression introduced in
2.6.39 -
if I switch back to a 2.6.38 kernel, my latency issues magically go
away! (I'm curious: does using the older 2.6.38.x kernel help with
anyone else that's seeing the issue?)
Some hardware/configuration details:
btrfs on a single disc (Seagate Momentus XT hybrid), lzo compression
and
space cache enabled. Some snapshots in use.
I notice that in latencytop I'm seeing a lot of lines with (cropped)
traces like
sleep_on_page wait_on_page_bit read_extent_buffer_ 13.3 msec
0.5 %
showing up that I didn't see with the 2.6.38 kernel. I occasionally
see
latencies as bad as 20-30 seconds on operations like fsync or
synchronous writes.
I think I can reproduce the issue well enough to bisect it, so I
might
give that a try. It'll be slow going, though.
You are right. This seems to be a regression in the .39 kernel. I
tested with 2.6.38.2 just now and the performance is back to normal.
Thanks,
Henning
server ~ # uname -a
Linux server 2.6.38.2 #1 SMP Thu Apr 14 13:05:35 CEST 2011 x86_64 AMD
Athlon(tm) 64 X2 Dual Core Processor 4200+ AuthenticAMD GNU/Linux
server ~ # sync; time sync
real 0m0.144s
user 0m0.000s
sys 0m0.020s
server ~ # bonnie++ -d tmp -u 0:0
Version 1.96 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
/sec %CP
server 16G 147 97 279933 56 73245 34 1258 78 102379 23
177.3 50
Latency 423ms 103ms 645ms 163ms 404ms
264ms
Version 1.96 ------Sequential Create------ --------Random
Create--------
server -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
/sec %CP
16 3784 28 +++++ +++ 8519 60 13694 59 +++++ +++
11710 76
Latency 127ms 1024us 18718us 15958us 119us
2459us
1.96,1.96,server,1,1308745595,16G,,147,97,279933,56,73245,34,1258,78,102379,23,177.3,50,16,,,,,3784,28,+++++,+++,8519,60,13694,59,+++++,+++,11710,76,423ms,103ms,645ms,163ms,404ms,264ms,127ms,1024us,18718us,15958us,119us,2459us
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