Bug 49691

Summary:	loadavg spikes in kernel 3.2.24 (and all later).
Product:	Process Management	Reporter:	spamik
Component:	Other	Assignee:	process_other
Status:	NEW ---
Severity:	low	CC:	alan
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	3.2.24 and later	Subsystem:
Regression:	No	Bisected commit-id:

Description spamik 2012-10-28 15:17:40 UTC

http://i.imgur.com/s3Asc.png

I'm seeing that issue on multiple servers. When I change kernel from 3.2.23 to: 3.6.3 3.4.15 3.2.32 and 3.2.27 I got this loadavg spikes every 1-3 hours (see png). Somewere between <3.2.24;3.2.27> something must have gone wrong
Those load spikes are about 40%sys and 40%usr load, loadavg spikes from 0,3 (very idle system) to 35 for a 1 second and then falls quicly.

Comment 1 spamik 2012-11-03 12:49:29 UTC

Through long and painfull process I've determined that
3.2.23 - works fine
3.2.24 - has this bug

Can you check what changes in 3.2.24 could be responsible for such loadavg spikes?

Comment 2 spamik 2012-11-03 13:29:35 UTC

I've made diff and I see that 3.2.24 is a version where leap seconds were fixed. Perhaps there are some unintended consequences of that that causes this problem? Something that does not play well with core distribution files (I use old centos 5.2 and only update services that are accessible from web).

Comment 3 spamik 2012-11-05 14:33:11 UTC

I see that 3.2.24 did some changes to NO_HZ. When I recompiled with CONFIG_NO_HZ=n problem went away. Why was it there in first place?