Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 21 Dec 2021 18:04:36 +0100 | Subject | Re: cpufreq: intel_pstate: map utilization into the pstate range |
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On Sun, Dec 19, 2021 at 11:10 PM Francisco Jerez <currojerez@riseup.net> wrote: > > Julia Lawall <julia.lawall@inria.fr> writes: > > > On Sat, 18 Dec 2021, Francisco Jerez wrote:
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> > I did some experiements with forcing different frequencies. I haven't > > finished processing the results, but I notice that as the frequency goes > > up, the utilization (specifically the value of > > map_util_perf(sg_cpu->util) at the point of the call to > > cpufreq_driver_adjust_perf in sugov_update_single_perf) goes up as well. > > Is this expected? > > > > Actually, it *is* expected based on our previous hypothesis that these > workloads are largely latency-bound: In cases where a given burst of CPU > work is not parallelizable with any other tasks the thread needs to > complete subsequently, its overall runtime will decrease monotonically > with increasing frequency, therefore the number of instructions executed > per unit of time will increase monotonically with increasing frequency, > and with it its frequency-invariant utilization.
But shouldn't these two effects cancel each other if the frequency-invariance mechanism works well?
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