Messages in this thread | | | Date | Fri, 29 Apr 2016 13:50:33 -0700 | Subject | Re: [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch() scheduler hook | From | David Carrillo-Cisneros <> |
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That's a possibility, although it will increase the distance between pmu->add for other perf events and the effective time that CQM monitoring starts.
On Fri, Apr 29, 2016 at 1:21 PM, Vikas Shivappa <vikas.shivappa@linux.intel.com> wrote: > > > On Fri, 29 Apr 2016, David Carrillo-Cisneros wrote: > >> (Re-sending in plain text) >> >> This hook is used in the following patch in the series to write to >> PQR_ASSOC_MSR, a msr that is utilized both by CQM/CMT and by CAT. >> Since CAT is not dependent on perf, I created this hook to start CQM >> monitoring right after other events start while keeping it independent >> of perf. The idea is to have future versions of CAT to also rely on >> this hook. > > > CAT did the msr write in switch_to as Peter did not want a new hook to be > used. Same could be done here. > > Thanks, > Vikas > > >> >> On Fri, Apr 29, 2016 at 11:05 AM, David Carrillo-Cisneros >> <davidcc@google.com> wrote: >>> >>> This hook is used in the following patch in the series to write to >>> PQR_ASSOC_MSR, a msr that is utilized both by CQM/CMT and by CAT. Since >>> CAT >>> is not dependent on perf, I created this hook to start CQM monitoring >>> right >>> after other events start while keeping it independent of perf. The idea >>> is >>> to have future versions of CAT to also rely on this hook. >>> >>> On Fri, Apr 29, 2016 at 1:52 AM Peter Zijlstra <peterz@infradead.org> >>> wrote: >>>> >>>> >>>> On Thu, Apr 28, 2016 at 09:43:31PM -0700, David Carrillo-Cisneros wrote: >>>>> >>>>> This hook allows architecture specific code to be called at the end of >>>>> the task switch and after perf_events' context switch but before the >>>>> scheduler lock is released. >>>>> >>>>> The specific use case in this series is to avoid multiple writes to a >>>>> slow >>>>> MSR until all functions which modify such register in task switch have >>>>> finished. >>>> >>>> >>>> Yeah, no. This really need way more justification. Why can't you use the >>>> regular perf sched-in stuff for CQM? >> >> >
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