Messages in this thread | | | Date | Thu, 17 Dec 2009 16:47:42 +0100 | From | Arjan van de Ven <> | Subject | Re: x264 benchmarks BFS vs CFS |
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On Thu, 17 Dec 2009 13:08:26 +0100 Ingo Molnar <mingo@elte.hu> wrote: > > > > not to mention that bfs does this whilst not loosing interactivity, > > something which cfs certainly cannot boast. > > What kind of latencies are those? Arent they just compiz induced due > to different weighting of workloads in BFS and in the upstream > scheduler? Would you be willing to help us out pinning them down? > > To move the discussion to the numeric front please send the 'perf > sched latency' output of an affected workload.
CFS in .32 and before has one known, and now fixed latency issue. In .32, wake_up() (which is most causes for inter thread communication and lots of others) was trying to keep the waker and wakee on the same logical cpu at pretty much all cost. In .33-git, Mike fixed this to, if there's a free logical cpu sibling, or on a multicore cpu, another core which shares the cache, to just schedule the new task on that free cpu rather than on the current, guaranteed busy, cpu.
This change helps latency a lot, and as a result, performance for various latency sensitive workloads...
-- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org
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