Messages in this thread |  | | Date | Thu, 14 Feb 2013 11:13:48 +0800 | From | Alex Shi <> | Subject | Re: [patch v4 05/18] sched: quicker balancing on fork/exec/wake |
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On 02/12/2013 06:22 PM, Peter Zijlstra wrote: > On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote: >> Guess the search cpu from bottom to up in domain tree come from >> commit 3dbd5342074a1e sched: multilevel sbe sbf, the purpose is >> balancing over tasks on all level domains. >> >> This balancing cost too much if there has many domain/groups in a >> large system. >> >> If we remove this code, we will get quick fork/exec/wake with a >> similar >> balancing result amony whole system. >> >> This patch increases 10+% performance of hackbench on my 4 sockets >> SNB machines and about 3% increasing on 2 sockets servers. >> >> > Numbers be groovy.. still I'd like a little more on the behavioural > change. Expand on what exactly is lost by this change so that if we > later find a regression we have a better idea of what and how. > > For instance, note how find_idlest_group() isn't symmetric wrt > local_group. So by not doing the domain iteration we change things. > > Now, it might well be that all this is somewhat overkill as it is, but > should we then not replace all of it with a simple min search over all > eligible cpus; that would be a real clean up. >
Um, will think this again.. >
-- Thanks Alex
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