Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH] percpu data: only iterate over possible CPUs | Date | Fri, 10 Feb 2006 13:10:58 +0100 |
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On Friday 10 February 2006 11:42, Andrew Morton wrote: > Andi Kleen <ak@muc.de> wrote: > > > > On Thursday 09 February 2006 19:04, Andrew Morton wrote: > > > Ashok Raj <ashok.raj@intel.com> wrote: > > > > > > > > The problem was with ACPI just simply looking at the namespace doesnt > > > > exactly give us an idea of how many processors are possible in this platform. > > > > > > We need to fix this asap - the performance penalty for HOTPLUG_CPU=y, > > > NR_CPUS=lots will be appreciable. > > > > What is this performance penalty exactly? > > All those for_each_cpu() loops will hit NR_CPUS cachelines instead of > hweight(cpu_possible_map) cachelines.
But are there any in real fast paths? iirc they are mostly in initialization, where it doesn't matter too much.
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