Messages in this thread | | | Date | Mon, 25 Apr 2016 23:34:51 +0200 | Subject | Re: [RFC PATCH 3/4] intel_pstate: support scheduler cpufreq callbacks on remote CPUs | From | "Rafael J. Wysocki" <> |
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On Thu, Apr 21, 2016 at 4:20 AM, Steve Muckle <steve.muckle@linaro.org> wrote: > On Wed, Apr 20, 2016 at 02:37:18PM +0200, Rafael J. Wysocki wrote: > ... >> > @@ -1173,20 +1179,88 @@ static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu) >> > get_avg_frequency(cpu)); >> > } >> > >> > +static void _intel_pstate_update_util(struct cpudata *cpu, u64 time) >> >> What about calling this intel_pstate_update_cpu()? > > Sure will change. > > ... >> > static void intel_pstate_update_util(struct update_util_data *data, u64 time, >> > unsigned long util, unsigned long max) >> > { >> > struct cpudata *cpu = container_of(data, struct cpudata, update_util); >> > - u64 delta_ns = time - cpu->sample.time; >> > + s64 delta_ns = time - cpu->sample.time; >> > >> > - if ((s64)delta_ns >= pid_params.sample_rate_ns) { >> > - bool sample_taken = intel_pstate_sample(cpu, time); >> > + if (delta_ns < pid_params.sample_rate_ns) >> >> Why don't you check cpu->ipi_in_progress here too and bail out if it is set? >> >> That would allow you to avoid checking the time again below, woulnd't it? > > Yeah I think that should work. I can't recall why I thought I needed > to check the time first, then ipi_in_progress, then the time. As long > as ipi_in_progress is checked prior to the time, it should be fine.
I actually think that we can just skip all cross-CPU updates in intel_pstate instead of adding complexity to it.
The governor algorithm here uses feedback registers to estimate utilization and I don't think it will react to the corss-CPU updates the way you want plus it is likely to skip them anyway due to the rate limit.
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