Messages in this thread | | | Date | Fri, 11 May 2007 18:52:49 +0200 | From | Eric Dumazet <> | Subject | Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex |
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Ingo Molnar a écrit : > * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > >> I was toying with a scalable rw_mutex and found that it gives ~10% >> reduction in system time on ebizzy runs (without the MADV_FREE patch). >> >> 2-way x86_64 pentium D box: >> >> 2.6.21 >> >> /usr/bin/time ./ebizzy -m -P >> 59.49user 137.74system 1:49.22elapsed 180%CPU (0avgtext+0avgdata 0maxresident)k >> 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps >> >> 2.6.21-rw_mutex >> >> /usr/bin/time ./ebizzy -m -P >> 57.85user 124.30system 1:42.99elapsed 176%CPU (0avgtext+0avgdata 0maxresident)k >> 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps > > nice! This 6% runtime reduction on a 2-way box will i suspect get > exponentially better on systems with more CPUs/cores.
As long you only have readers, yes.
But I personally find this new rw_mutex not scalable at all if you have some writers around.
percpu_counter_sum is just a L1 cache eater, and O(NR_CPUS)
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