Messages in this thread | | | Date | Thu, 10 Jul 2008 22:24:53 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC 00/15] x86_64: Optimize percpu accesses |
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* Eric W. Biederman <ebiederm@xmission.com> wrote:
> Mike Travis <travis@sgi.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
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