linux-kernel - Re: [PATCH v3 5/5] cpusets, suspend: Save and restore cpusets during suspend/resume

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Message-ID: <1337116407.27694.118.camel@twins>
Date:	Tue, 15 May 2012 23:13:27 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	mingo@...nel.org, pjt@...gle.com, paul@...lmenage.org,
	akpm@...ux-foundation.org, rjw@...k.pl, nacc@...ibm.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 v3 5/5] cpusets, suspend: Save and restore cpusets
 during suspend/resume

On Tue, 2012-05-15 at 14:05 -0700, David Rientjes wrote:
> Not sure what you're disagreeing with, it only happens with 
> MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES and I've clearly defined the 
> behavior in the man page.  I personally never had a use-case for 
> MPOL_F_RELATIVE_NODES but Paul Jackson asked that it be added for SGI when 
> we added mempolicy mode flags. 

So what you're saying is that:

task t: set_mempolicy(,mask=2-3);

add t to cpuset A

A.mems = 0-1
A.mems = 0-n

At which point t will again have 2-3, right?

My objection is that you'll have to keep the 2-3 mask around some place
because t->mems_allowed will be wrecked by cpuset actions.

Also, what does it mean to silently return to 2-3 after you've broken
that promise by forcing it to 0-1 using cpusets?


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