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Date: Mon, 22 Nov 2010 06:51:29 +0100 From: Florian Mickler <florian@...kler.org> To: Peter Zijlstra <peterz@...radead.org> Cc: John Stultz <john.stultz@...aro.org>, lkml <linux-kernel@...r.kernel.org>, Mike Chan <mike@...roid.com>, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH 3/5] scheduler: cpuacct: Enable platform hooks to track cpuusage for CPU frequencies On Sat, 20 Nov 2010 11:48:24 +0100 Peter Zijlstra <peterz@...radead.org> wrote: > On Fri, 2010-11-19 at 18:08 -0800, John Stultz wrote: > > From: Mike Chan <mike@...roid.com> > > > > Introduce new platform callback hooks for cpuacct for tracking CPU frequencies > > > > Not all platforms / architectures have a set CPU_FREQ_TABLE defined > > for CPU transition speeds. In order to track time spent in at various > > CPU frequencies, we enable platform callbacks from cpuacct for this accounting. > > > > Architectures that support overclock boosting, or don't have pre-defined > > frequency tables can implement their own bucketing system that makes sense > > given their cpufreq scaling abilities. > > > > New file: > > cpuacct.cpufreq reports the CPU time (in nanoseconds) spent at each CPU > > frequency. > > I utterly detest all such accounting crap.. it adds ABI constraints it > add runtime overhead. etc.. > > Can't you get the same information by using the various perf bits? If > you trace the cpufreq changes you can compute the time spend in each > power state, if you additionally trace the sched_switch you can compute > it for each task. > > This is probably used for "on-site" debugging of production systems. I.e. when someone sends them a problem report using an bugreport-tool, they gather all useful information they can get on the system because they only have one-way communication with their bug reporters. Do the perf bits work for such a usecase? If I guess correctly, the perf bits need a userspace part that computes what would be in the cpuacct.cpufreq file? Regards, Flo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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