Bug 1016797

Summary: ksoftirqd hogs cpu with 3.10 kernel
Product: [Fedora] Fedora Reporter: Mattia Verga <mattia.verga>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 19CC: floydbarber, gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda, marcelo.barbosa, mattia.verga, sagarun
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Hardware: x86_64   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2014-01-05 08:16:33 UTC Type: Bug
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Description Mattia Verga 2013-10-08 17:21:19 UTC 
My system is constantly under heavy load because I use Boinc. Since the introduction of 3.10.x series kernel I've noticed that ksoftirqd hogs the cpu: it eats from 8% to 16% of every cpu core under heavy load and sometimes the system hangs for a couple of seconds.

Googling around I found more reports of users having this problem after the transition from 3.9 to 3.10 kernel. A couple of discussion I found are:
https://lkml.org/lkml/2013/8/20/37
http://forums.gentoo.org/viewtopic-t-965336-start-0.html
The secon iteresting, they're pointing out this can be a problem related to kernel being built with "full-tickless" settings (I admit I don't know what they're talking about...)

I tried to add the "nohz=off" parameter in grub at startup, but it don't fix my problem.
Comment 1 Arun S A G 2013-10-12 12:11:53 UTC 
kernel 3.11 is out for a while, have you tried updating to it? Bug still exists with 3.11?
Comment 2 Mattia Verga 2013-10-12 15:53:16 UTC 
Created attachment 811588 [details]
top output

Yes, today I've also tried with 3.11.4 from updates-testing, same problem.
The attachment shows the output of top with kernel 3.11.4
Comment 3 Justin M. Forbes 2014-01-03 22:07:19 UTC 
*********** MASS BUG UPDATE **************

We apologize for the inconvenience.  There is a large number of bugs to go through and several of them have gone stale.  Due to this, we are doing a mass bug update across all of the Fedora 19 kernel bugs.

Fedora 19 has now been rebased to 3.12.6-200.fc19.  Please test this kernel update (or newer) and let us know if you issue has been resolved or if it is still present with the newer kernel.

If you have moved on to Fedora 20, and are still experiencing this issue, please change the version to Fedora 20.

If you experience different issues, please open a new bug report for those.
Comment 4 Mattia Verga 2014-01-05 08:16:33 UTC 
Seems things are slightly well now. I still get ksoftirqd using from 6% to 8% of each core, but only when using GPU computing under boinc, maybe it's something to due with AMD catalyst drivers.
I will close the bug.