From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 23 Nov 2005 19:02:37 -0800 From: Paul Jackson Subject: Re: [PATCH]: Free pages from local pcp lists under tight memory conditions Message-Id: <20051123190237.3ba62bf0.pj@sgi.com> In-Reply-To: <1132779605.25086.69.camel@akash.sc.intel.com> References: <20051122161000.A22430@unix-os.sc.intel.com> <1132775194.25086.54.camel@akash.sc.intel.com> <20051123115545.69087adf.akpm@osdl.org> <1132779605.25086.69.camel@akash.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rohit Seth Cc: akpm@osdl.org, clameter@engr.sgi.com, torvalds@osdl.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, steiner@sgi.com, nickpiggin@yahoo.com.au List-ID: Rohit wrote: > I thought Nick et.al came up with some of the constant values like batch > size to tackle the page coloring issue specifically. I think this came about on a linux-ia64 thread started by Jack Steiner: http://www.gelato.unsw.edu.au/archives/linux-ia64/0504/13668.html Subject: per_cpu_pagesets degrades MPI performance From: Jack Steiner Date: 2005-04-05 05:28:27 Jack reported that per_cpu_pagesets were degrading some MPI benchmarks due to adverse page coloring. Nick responded, recommending a non-power of two batch size. Jack found that this helped nicely. This thread trails off, but seems to be the origins of the 2**n-1 batch size in: mm/page_alloc.c:zone_batchsize() * Clamp the batch to a 2^n - 1 value. Having a power ... batch = (1 << fls(batch + batch/2)) - 1; I don't see here evidence that "per_cpu_pagelist is ... one single main reason the coloring effect is drastically reduced in 2.6 (over 2.4) based kernels." Rather in this case anyway a batch size not a power of two was apparently needed to keep per_cpu_pagesets from hurting performance due to page coloring affects on some workloads. -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org