Re: [PATCH 0 of 8] x86/smp function calls: convert x86 tlb flushesto use function calls
From: Jeremy Fitzhardinge
Date: Mon Aug 11 2008 - 19:57:58 EST
Andi Kleen wrote:
Micro benchmark. Just stick RDTSC around the calls and trigger
a few remote flushes by e.g. doing mmap/munmap on a multithreaded program
running on different CPUs.
On a HT 3GHz Xeon, I see a ~35% increase in time (1830ns -> 2500ns),
averaged over 1000,000 interrupts. Because it's only 2 cpu, it ends up
always using the smp_call_function_single path (but via the
smp_call_function_mask path).
I need to try getting a more-cpu machine running native to do a proper
test, esp to see if putting kmalloc on that path is very expensive or
not. (Is it worth using a kmem_cache?)
J
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