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SubjectRe: [PATCH v5 0/5] CPU hotplug, cpusets, suspend/resume: Fixes, cleanups and optimizations
Hi Peter,

Did you get a chance to take a look at this patchset?

(I have added a summary of the changes between the versions below.)

Thanks a lot!

On 05/17/2012 10:29 PM, Srivatsa S. Bhat wrote:

> Currently the kernel doesn't handle cpusets properly during suspend/resume.
> After a resume, all non-root cpusets end up having only 1 cpu (the boot cpu),
> causing massive performance degradation of workloads. One major user of cpusets
> is libvirt, which means that after a suspend/hibernation cycle, all VMs
> suddenly end up running terribly slow!
>
> Also, the kernel moves the tasks from one cpuset to another during CPU hotplug
> in the suspend/resume path, leading to a task-management nightmare after
> resume.
>
> Patch 1 fixes this by keeping cpusets unmodified in the suspend/resume path.
> But to ensure we don't trip over, it keeps the sched domains updated during
> every CPU hotplug in the s/r path.
> This is a long standing issue and we need to fix up stable kernels too.
>
> The rest of the patches in the series are mostly cleanups/optimizations
> (except patch 4 which is a non-critical bug fix).
>


Changelog:

v5 : Don't do explicit save/restore of cpusets' cpu masks during s/r, to avoid
the overhead of a new per-cpuset cpu mask to help with that. Also, ensure
that the sched domains are updated on each hotplug.
The s/r fix (patch 1) is now distinct from the cleanups (patches 2-5).

v4 : (Never had this version. I skipped from v3 to v5 accidentally).

v3 : Explicitly save and restore cpusets' cpu masks during s/r. Don't alter
the semantics of regular cpu hotplug.
http://thread.gmane.org/gmane.linux.kernel/1296339

v2 : http://thread.gmane.org/gmane.linux.documentation/4805/

v1 : thread.gmane.org/gmane.linux.kernel/1250097/


> --
> Srivatsa S. Bhat (5):
> CPU hotplug, cpusets, suspend: Don't modify cpusets during suspend/resume
> cpusets, hotplug: Implement cpuset tree traversal in a helper function
> cpusets, hotplug: Restructure functions that are invoked during hotplug
> cpusets: Update tasks' cpus_allowed mask upon updates to root cpuset
> cpusets: Remove/update outdated comments
>
>
> include/linux/cpuset.h | 4 +
> kernel/cpuset.c | 161 +++++++++++++++++++++++++++++++++++-------------
> kernel/sched/core.c | 44 +++++++++++--
> 3 files changed, 159 insertions(+), 50 deletions(-)


Regards,
Srivatsa S. Bhat



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