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Date: Mon, 30 Mar 2009 13:22:55 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Christoph Lameter <cl@...ux.com> cc: Pekka Enberg <penberg@...helsinki.fi>, Nick Piggin <nickpiggin@...oo.com.au>, Martin Bligh <mbligh@...gle.com>, linux-kernel@...r.kernel.org Subject: Re: [patch 2/3] slub: scan partial list for free slabs when thrashing On Mon, 30 Mar 2009, Christoph Lameter wrote: > > Whenever a cpu cache satisfies a fastpath allocation, a fastpath counter > > is incrememted. This counter is cleared whenever the slowpath is > > invoked. This tracks how many fastpath allocations the cpu slab has > > fulfilled before it must be refilled. > > That adds fastpath overhead and it shows for small objects in your tests. > Indeed, which is unavoidable in this case. The only other way of tracking the "thrashing history" I can think of would be bitshifting a 1 for slowpath and 0 for fastpath, for example, into an unsigned long. That, however, requires a hamming weight calculation in the slowpath and doesn't scale nearly as well as simply an incrementing a counter. If there's other approaches on tracking such instances, I'd be interested to hear them. Btw, is cl@...ux.com your new email address or are all linux-foundation.org emails going to eventually migrate to the new domain? -- 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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