linux-kernel - Re: [PATCH v6 0/4] CPU hotplug, cpusets, suspend/resume: Fixes, cleanups and optimizations

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Date:	Wed, 20 Jun 2012 13:39:17 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, pjt@...gle.com,
	paul@...lmenage.org, akpm@...ux-foundation.org, rjw@...k.pl,
	nacc@...ibm.com, rientjes@...gle.com, paulmck@...ux.vnet.ibm.com,
	tglx@...utronix.de, seto.hidetoshi@...fujitsu.com, tj@...nel.org,
	mschmidt@...hat.com, berrange@...hat.com,
	nikunj@...ux.vnet.ibm.com, vatsa@...ux.vnet.ibm.com,
	liuj97@...il.com, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v6 0/4] CPU hotplug, cpusets, suspend/resume: Fixes,
 cleanups and optimizations

* Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> wrote:

> On 05/24/2012 07:46 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.
> 
> Hi Peter,
> 
> Would you be taking these patches through -tip for 3.6?

They are now in tip:sched/core.

Note that I removed the Cc:stable tag - it's not a regression 
fix and such it is not eligible for immediate -stable backports.

( Once they are upstream and have been problem-free upstream for
  several weeks then *maybe* we could forward the first commit
  to -stable, as a super special exception. )

Thanks,

	Ingo
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