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Date: Thu, 19 Jul 2007 12:55:32 +0200 From: Adrian Bunk <bunk@...sta.de> To: Andi Kleen <ak@...e.de> Cc: Christoph Hellwig <hch@...radead.org>, kiran@...lex86.org, patches@...-64.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] [33/58] x86_64: Avoid too many remote cpu references due to /proc/stat On Thu, Jul 19, 2007 at 12:41:28PM +0200, Andi Kleen wrote: > On Thursday 19 July 2007 12:21:49 Christoph Hellwig wrote: > > On Thu, Jul 19, 2007 at 11:55:19AM +0200, Andi Kleen wrote: > > > > > > From: Ravikiran G Thirumalai <kiran@...lex86.org> > > > Too many remote cpu references due to /proc/stat. > > > > > > On x86_64, with newer kernel versions, kstat_irqs is a bit of a problem. > > > On every call to kstat_irqs, the process brings in per-cpu data from all > > > online cpus. Doing this for NR_IRQS, which is now 256 + 32 * NR_CPUS > > > results in (256+32*63) * 63 remote cpu references on a 64 cpu config. > > > /proc/stat is parsed by common commands like top, who etc, causing > > > lots of cacheline transfers > > > > > > This statistic seems useless. Other 'big iron' arches disable this. > > > Can we disable computing/reporting this statistic? This piece of > > > statistic is not human readable on x86_64 anymore, > > > > > > If not, can we optimize computing this statistic so as to avoid > > > too many remote references (patch to follow) > > > > If we disable this on x86_64 we should just kill it completely for consistency. > > I guess it's fine on UP only architectures. I will change it to !CONFIG_SMP > unless someone complains. Making it depending on the kernel configuration will only cause surprises for users. And if you really need the data you can get it from /proc/interrupts. > -Andi cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed - 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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