[libvirt] [PATCH 0/3] several cgroups/cpuset fixes

[John Ferlan]

On 01/11/2016 06:38 AM, Henning Schild wrote:
> On Fri, 8 Jan 2016 11:05:59 -0500
> John Ferlan <jferlan at redhat.com> 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.

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
>