Messages in this thread | | | Date | Fri, 24 Oct 2008 15:34:58 +0530 | From | Vaidyanathan Srinivasan <> | Subject | Re: [RFC PATCH v2 0/5] sched: modular find_busiest_group() |
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* Peter Zijlstra <peterz@infradead.org> [2008-10-14 15:25:03]:
> On Tue, 2008-10-14 at 18:37 +0530, Vaidyanathan Srinivasan wrote: > > * Peter Zijlstra <peterz@infradead.org> [2008-10-14 14:09:13]: > > > > > > > > Hi, > > > > > > So the basic issue is sched_group::cpu_power should become more dynamic. > > > > Hi Peter, > > > > This is a good idea. Dynamically increasing cpu power to some groups > > will automatically help power savings when we want to consolidate > > better to one cpu package when overall system utilisation is very low. > > Ah, yes another use case of this ;-) > > > > Dynamic Speed Technology > > > ------------------------ > > > > > > With cpus actively fiddling with their processing capacity we get into > > > similar issues. Again we can measure this, but this would require the > > > addition of a clock that measures work instead of time. > > > > > > Having that, we can even acturately measure the old SMT case, which has > > > always been approximated by a static percentage - even though the actual > > > gain is very workload dependent. > > > > > > The idea is to introduce sched_work_clock() so that: > > > > > > work_delta / time_delta gives the power for a cpu. <1 means we > > > did less work than a dedicated pipeline, >1 means we did more. > > > > The challenge here is measurement of 'work'. What will be the > > parameter that will be fair for most workloads and easy to measure on > > most systems? > > > > * Instructions completion count > > * APERF or similar CPU specific counter on x86 > > * POWER has PURR and SPURR to have a measure of relative work done > > Right - I was hoping for some feedback from the arch folks (maybe I > should have CC'ed linux-arch) on this issue.
Hi Peter,
Do you want to post this RFD again to get more feedback?
--Vaidy
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