From: Nick Piggin <npiggin@suse.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Lee@firstfloor.org, Schermerh@firstfloor.org
Subject: Re: [rfc] forked kernel task and mm structures imbalanced on NUMA
Date: Wed, 2 Jun 2010 01:59:43 +1000 [thread overview]
Message-ID: <20100601155943.GA9453@laptop> (raw)
In-Reply-To: <87wruiycsl.fsf@basil.nowhere.org>
On Tue, Jun 01, 2010 at 05:48:10PM +0200, Andi Kleen wrote:
> Nick Piggin <npiggin@suse.de> writes:
>
> > This isn't really a new problem, and I don't know how important it is,
> > but I recently came across it again when doing some aim7 testing with
> > huge numbers of tasks.
>
> Seems reasonable. Of course you need to at least
> save/restore the old CPU policy, and use a subset of it.
The mpolicy? My patch does that (mpol_prefer_cpu_start/end). The real
problem is that it can actually violate the parent's mempolicy. For
example MPOL_BIND and cpus_allowed set on a node outside the mempolicy.
What is needed is to execute with the existing mempolicy, but from
the point of view of the destination CPU. A bit more work on the
mpol code is required, but this is good enough for basic tests.
> Another approach would be to migrate this on touch, but that is probably
> slightly more difficult. The advantage would be that on multiple
> migrations it would follow. And it would be a bit slower for
> the initial case.
Migrate what on touch? Talking mainly about kernel memory structures,
task_struct, mm, vmas, page tables, kernel stack, etc.
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next prev parent reply other threads:[~2010-06-01 15:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-01 7:33 [rfc] forked kernel task and mm structures imbalanced on NUMA Nick Piggin
2010-06-01 8:16 ` Peter Zijlstra
2010-06-01 8:41 ` Nick Piggin
2010-06-01 9:05 ` Peter Zijlstra
2010-06-01 8:49 ` Peter Zijlstra
2010-06-01 15:48 ` Andi Kleen
2010-06-01 15:59 ` Nick Piggin [this message]
2010-06-01 16:20 ` Andi Kleen
2010-06-01 16:31 ` Nick Piggin
2010-06-01 16:00 ` Peter Zijlstra
2010-06-01 16:02 ` Peter Zijlstra
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