Message-ID: <1337356192.573.75.camel@twins>
Subject: Re: [tip:sched/numa] sched/numa: Introduce sys_numa_{t,m}bind()
From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>, mingo@kernel.org, hpa@zytor.com,
        linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
        pjt@google.com, bharata.rao@gmail.com, akpm@linux-foundation.org,
        Lee.Schermerhorn@hp.com, aarcange@redhat.com, danms@us.ibm.com,
        suresh.b.siddha@intel.com, tglx@linutronix.de,
        linux-tip-commits@vger.kernel.org
Date: Fri, 18 May 2012 17:49:52 +0200
In-Reply-To: <alpine.DEB.2.00.1205181047030.21093@router.home>
References: <tip-nf7brf1b88w0ojwuf689xeet@git.kernel.org>
	 <4FB66756.2060302@redhat.com> <1337355341.573.68.camel@twins>
	 <1337355610.573.70.camel@twins>
	 <alpine.DEB.2.00.1205181047030.21093@router.home>
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On Fri, 2012-05-18 at 10:47 -0500, Christoph Lameter wrote:
> On Fri, 18 May 2012, Peter Zijlstra wrote:
> 
> > On Fri, 2012-05-18 at 17:35 +0200, Peter Zijlstra wrote:
> > > I've also said many times over that I absolutely detest all the async
> > > stuff because it messes up accounting. And until someone comes up with a
> > > sane means of sorting that I'll stick to migrate-on-fault.
> >
> > The other nice advantage of migrate-on-fault is that you don't have to
> > play lifetime games with vmas. This much simplifies that aspect.
> 
> The problem with migrate on fault in the past has been that there was no
> consistent benefit from the overhead added to the system. Useless page
> migration is a bit expensive.

I'm not sure I follow.. having the page local is a win, presuming you
can limit the migration rate to something low in relation to the cost of
remote accesses.

How does it matter how you migrate?
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