From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 4 Oct 2006 19:53:13 -0700 From: Paul Jackson Subject: Re: [RFC] another way to speed up fake numa node page_alloc Message-Id: <20061004195313.892838e4.pj@sgi.com> In-Reply-To: References: <20060925091452.14277.9236.sendpatchset@v0> <20061001231811.26f91c47.pj@sgi.com> <20061001234858.fe91109e.pj@sgi.com> <20061002014121.28b759da.pj@sgi.com> <20061003111517.a5cc30ea.pj@sgi.com> <20061004084552.a07025d7.pj@sgi.com> <20061004192714.20412e08.pj@sgi.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: David Rientjes Cc: linux-mm@kvack.org, akpm@osdl.org, nickpiggin@yahoo.com.au, ak@suse.de, mbligh@google.com, rohitseth@google.com, menage@google.com, clameter@sgi.com List-ID: David wrote: > The only change that would be required is > to abstract a macro to test against if NUMA emulation was configured > correctly at boot-time instead of just NUMA_BUILD. Why add any logic to avoid this zonelist caching on systems not using numa emulation? Leaving this zonelist caching enabled all the time: 1) improves test coverage of it, and 2) benefits those real numa systems that might have long zonelist scans in the future. My experience on my current customer base with cpusets is almost entirely with HPC (High Performance Computing) apps, which usually manage their memory layout very closely. These workloads would tend to have very short zonelist scans and benefit little from this speed up. As cpusets gets wider use on more varied workloads, I would expect that some of these varied workloads would stress the zonelist scanning more. And there's still a pretty good chance, though I can't document it, that we've already seen performance problems, even on existing HPC workloads, with this zonelist scan. So ... I ask again ... why avoid this speed up on systems not emulating nodes? -- 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