Messages in this thread | | | Date | Fri, 22 Feb 2013 12:46:54 +0800 | From | Alex Shi <> | Subject | Re: [RFC PATCH v3 1/3] sched: schedule balance map foundation |
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On 02/22/2013 12:19 PM, Michael Wang wrote: > >> > Why not seek other way to change O(n^2) to O(n)? >> > >> > Access 2G memory is unbelievable performance cost. > Not access 2G memory, but (2G / 16K) memory, the sbm size is O(N). > > And please notice that on 16k cpus system, topology will be deep if NUMA > enabled (O(log N) as Peter said), and that's really a good stage for > this idea to perform on, we could save lot's of recursed 'for' cycles. >
CPU execute part is very very fast compare to the memory access, the 'for' cycles cost is most on the memory access for many domain/groups data, not instruction execution.
In a hot patch, several KB memory access will cause clear cpu cache pollution then make kernel slowly.
-- Thanks Alex
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