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Date: Thu, 10 Jul 2008 22:24:53 +0200 From: Ingo Molnar <mingo@...e.hu> To: "Eric W. Biederman" <ebiederm@...ssion.com> Cc: Mike Travis <travis@....com>, "H. Peter Anvin" <hpa@...or.com>, Christoph Lameter <cl@...ux-foundation.org>, Jeremy Fitzhardinge <jeremy@...p.org>, Andrew Morton <akpm@...ux-foundation.org>, Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org, Arjan van de Ven <arjan@...radead.org> Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses * Eric W. Biederman <ebiederm@...ssion.com> wrote: > Mike Travis <travis@....com> writes: > > > > The biggest growth came from moving all the xxx[NR_CPUS] arrays into > > the per cpu area. So you free up a huge amount of unused memory > > when the NR_CPUS count starts getting into the ozone layer. 4k now, > > 16k real soon now, ??? future? > > Hmm. Do you know how big a role kernel_stat plays. > > It is a per cpu structure that is sized via NR_IRQS. NR_IRQS is by > NR_CPUS. So ultimately the amount of memory take up is > NR_CPUS*NR_CPUS*32 or so. > > I have a patch I wrote long ago, that addresses that specific nasty > configuration by moving the per cpu irq counters into pointer > available from struct irq_desc. > > The next step which I did not get to (but is interesting from a > scaling perspective) was to start dynamically allocating the irq > structures. /me willing to test & babysit any test-patch in that area ... this is a big problem and it's getting worse quadratically ;-) Ingo -- 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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