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Message-ID: <45E9AD74.4060704@mbligh.org>
Date: Sat, 03 Mar 2007 09:16:36 -0800
From: "Martin J. Bligh" <mbligh@mbligh.org>
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To: Christoph Lameter <clameter@engr.sgi.com>
Cc: William Lee Irwin III <wli@holomorphy.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Rik van Riel <riel@redhat.com>, Bill Irwin <bill.irwin@oracle.com>,
       Mel Gorman <mel@skynet.ie>, npiggin@suse.de, mingo@elte.hu,
       jschopp@austin.ibm.com, arjan@infradead.org,
       torvalds@linux-foundation.org, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org
Subject: Re: The performance and behaviour of the anti-fragmentation related
 patches
References: <20070302093501.34c6ef2a.akpm@linux-foundation.org> <45E8624E.2080001@redhat.com> <20070302100619.cec06d6a.akpm@linux-foundation.org> <Pine.LNX.4.64.0703021012170.17676@schroedinger.engr.sgi.com> <45E86BA0.50508@redhat.com> <20070302211207.GJ10643@holomorphy.com> <45E894D7.2040309@redhat.com> <20070302135243.ada51084.akpm@linux-foundation.org> <45E89F1E.8020803@redhat.com> <20070302142256.0127f5ac.akpm@linux-foundation.org> <20070303003319.GB23573@holomorphy.com> <Pine.LNX.4.64.0703021913030.31787@schroedinger.engr.sgi.com>
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Christoph Lameter wrote:
> On Fri, 2 Mar 2007, William Lee Irwin III wrote:
> 
>> On Fri, Mar 02, 2007 at 02:22:56PM -0800, Andrew Morton wrote:
>>> Opterons seem to be particularly prone to lock starvation where a cacheline
>>> gets captured in a single package for ever.
>> AIUI that phenomenon is universal to NUMA. Maybe it's time we
>> reexamined our locking algorithms in the light of fairness
>> considerations.
> 
> This is a phenomenon that is usually addressed at the cache logic level. 
> Its a hardware maturation issue. A certain package should not be allowed
> to hold onto a cacheline forever and other packages must have a mininum 
> time when they can operate on that cacheline.

That'd be nice. Unfortunately we're stuck in the real world with
real hardware, and the situation is likely to remain thus for
quite some time ...

M.