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Bug 239289 - irqbalance consumes all 100% CPU on Xen domain 0
irqbalance consumes all 100% CPU on Xen domain 0
Product: Fedora
Classification: Fedora
Component: irqbalance (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Neil Horman
Depends On:
  Show dependency treegraph
Reported: 2007-05-07 09:17 EDT by Aleksander Adamowski
Modified: 2008-02-26 19:10 EST (History)
0 users

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-02-26 19:10:56 EST
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RHEL 7.3 requirements from Atomic Host:
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Description Aleksander Adamowski 2007-05-07 09:17:40 EDT
Description of problem:

We have to servers running Fedora Core 5 with Xen kernel and several guest domains.

Lately, the irqbalance daemons running on zero domains pm those servers have
started consuming all available CPU. It probably occured after some update, but
we cannot determine that - we'd have to reboot those machines, and they are
constantly in use.

Here's the output from xentop:

xentop - 15:11:52   Xen 3.0.3-0-1.2316.fc5
12 domains: 1 running, 11 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown 
Mem: 6119000k total, 5739120k used, 379880k free    CPUs: 4 @ 1804MHz
      NAME  STATE   CPU(sec) CPU(%)     MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%) VCPUS
  Domain-0 -----r     247351  100.5     523160    8.5   no limit       n/a     4
   4  2580863   327865    0        0        0        0    0
.... then the guest domains - they consume 1.6% CPU max.

Version-Release number of selected component (if applicable):
kernel-xen0-2.6.20-1.2316.fc5 on one machine, kernel-xen0-2.6.18-1.2239.fc5 on
the other

How reproducible:

Immediately after reboot, 100% of the time
Comment 1 Neil Horman 2007-05-07 09:38:57 EDT
Can you please try upgrading to irqbalance-0.55-3.fc7?  Its a complete rewrite
and should correct lots of these sorts of problems.  If it works I'll try to get
it into FC-5 if I'm able.

Note the version number is lower than the current fc5 release.  I've set the
epoch to make the upgrade transparent in the fc7 version.
Comment 2 Aleksander Adamowski 2007-05-24 05:00:57 EDT
should I install it on the domain 0, or on the guests as well?
Comment 3 Neil Horman 2007-05-24 06:50:19 EDT
you shouldn't be running irqbalance on the guests, just on the dom0
Comment 4 Aleksander Adamowski 2007-05-24 10:59:00 EDT
I couldn't find irqbalance-0.55-3.fc7 anywhere yet, so I've compiled and
installed irqbalance-0.55-2.fc7 from

Then stopped and started irqbalance service (no reboot since the machine hosts
some minor services). It doesn't consume all CPU anymore. But how can I verify
that it in fact does its job, balancing IRQ?

Comment 5 Neil Horman 2007-05-24 12:38:27 EDT
the same way you would have verified it previously: look at
/proc/irq/<irqnum>/smp_affinity and look to see that the value contained in
those files is something other than all f's

Comment 6 Aleksander Adamowski 2007-05-24 20:15:50 EDT
Seems it works:

# find /proc/irq -type f -name smp_affinity | xargs cat | sort | uniq -c
    500 01
      4 02
      3 04
      3 08
      2 0f

Doesn't excessively consume CPU now - I think it can be released into FC5.
Comment 7 Neil Horman 2007-05-25 09:32:53 EDT
Comment 8 Chris Lalancette 2008-02-26 19:10:56 EST
This report targets FC5, which is now end-of-life.

Please re-test against Fedora 7 or later, and if the issue persists, open a new bug.


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