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Date: Wed, 9 May 2007 16:10:05 -0700 From: "Yu, Fenghua" <fenghua.yu@...el.com> To: "Christoph Lameter" <clameter@....com>, "Andrew Morton" <akpm@...ux-foundation.org> CC: "Siddha, Suresh B" <suresh.b.siddha@...el.com>, <linux-kernel@...r.kernel.org> Subject: RE: [PATCH 2/2] Call percpu smp cacheline algin interface On Wed, 9 May 2007, Andrew Morton wrote: >> erm, it's not obviosu from all this that the patches are worth proceeding >> with, are they? >What was it? 0.5% performance improvement on a synthetic benchmark? >Process wakeup I believe? The initial patch and discussion is from: http://www.uwsg.iu.edu/hypermail/linux/kernel/0704.1/0340.html Yes, the runqueue patch has a 0.5% perf improvement on database workload(which is a good improvement for this workload). The theory behind the patches is: 1. Minimize number of cache lines that are touched during a remote access. On Numa system, remote access is more expensive than local. 2. Do not share cache line between remote accessed data and local accessed data. Local data update may cause remote access cache miss and wait for longer time. Although the patches themselves don't save or waste per_cpu size, the above two reasons are good to have them in. Thanks. -Fenghua - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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