Re: [PATCH 0/3] several cgroups/cpuset fixes

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On Mon, 11 Jan 2016 07:05:11 -0500
John Ferlan <jferlan@xxxxxxxxxx> wrote:

> 
> 
> On 01/11/2016 06:38 AM, Henning Schild wrote:
> > On Fri, 8 Jan 2016 11:05:59 -0500
> > John Ferlan <jferlan@xxxxxxxxxx> wrote:
> > 
> >>
> >>>>
> >>>> I'm leaning towards something in the test. I'll check if
> >>>> reverting these changes alters the results. I don't imagine it
> >>>> will.
> >>>
> >>> The real question is which thread it fails on and at what point in
> >>> time. My patches only changed the order of operations where
> >>> threads enter the cpuset cgroups at a slightly different time.
> >>> And the qemu main thread never enters the parent group, it
> >>> becomes an emulator-thread. Maybe you can point to exactly the
> >>> assertion that fails. Including a link to the test code. And yes
> >>> if you can confirm that the patches are to blame that would be a
> >>> good first step ;).
> >>>
> >>> Thanks,
> >>> Henning
> >>>
> >>
> >> Update:
> >>
> >> I have found that if I revert patch 2...
> >>
> >> Then modify qemuInitCgroup() to modify the virCgroupNewMachine
> >> check to also ensure "|| !priv->cgroup)
> > 
> > I see the check for the parent cgroup should probably go back into
> > virCgroupNewMachine, including the cleanup stuff in case of failure.
> > 
> 
> Forgot to CC you (and Jan) on the 4 patch series I sent:
> 
> http://www.redhat.com/archives/libvir-list/2016-January/msg00236.html
> 
> Patches 2, 3, & 4 are related to above while patch 1 is for below.

If you are subscribed could you please send me a copy of the mails - as
received on the list, for review?
 
> John
> 
> >> Then modify qemuSetupCgroupForEmulator() to make the
> >> virCgroupAddTask() call like was in patch 2
> >>
> >> Then modify patch 3 (qemuSetupCgroupForVcpu) to change the call:
> >>
> >>
> >>              if (!cpumap)
> >>                  continue;
> >>
> >>              if (qemuSetupCgroupCpusetCpus(cgroup_vcpu, cpumap) <
> >> 0) goto cleanup;
> >>
> >> to
> >>
> >>              if (cpumap &&
> >>                  qemuSetupCgroupCpusetCpus(cgroup_vcpu, cpumap) <
> >> 0) goto cleanup;
> >>
> > 
> > Well that is not a syntactical change, maybe easier to read and in
> > line with the other places where qemuSetupCgroupCpusetCpus is
> > called.
> > 
> >> Then retest and the test passes again.
> >>
> >> Note that taking this route, I found that when I start the guest, I
> >> have the following in 'tasks':
> >>
> >> # cat /sys/fs/cgroup/memory/machine.slice/tasks
> >> # cat /sys/fs/cgroup/memory/machine.slice/*/tasks
> >> 15007
> >> 15008
> >> 15010
> >> 15011
> >> 15013
> >> #
> >>
> >> Where '15007' is the virt-tests-vm1 process
> >> (eg, /proc/$pid/cgroup). If I read the intentions you had, this
> >> follows that...
> >>
> >> I'll post a couple of patches in a bit...
> >>
> >> John
> > 

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