Messages in this thread | | | Date | Tue, 9 Sep 2014 11:56:18 +0530 | Subject | Re: [PATCH] intel_pstate: track and export frequency residency stats via sysfs. | From | Viresh Kumar <> |
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On Tue, Sep 9, 2014 at 11:02 AM, Anup Chenthamarakshan <anupc@chromium.org> wrote: > I had initially tried reusing cpufreq_stats.c to export stats. > Calling cpufreq_stats_update() via the cpufreq notifier added > some amount of overhead while switching frequencies. Specifically, > looking up the index of the new frequency in freq_table_get_index() > is a linear search through all available frequencies (vs a single > subtraction with custom stats export). Also, the notifier mechanism
I don't think just this linear search will make things so bad..
> itself added a level of indirection before calling stats_update.
Probably some other notifier is registered which is taking considerable amount of time.. Try checking what all registered with cpufreq-core.
> There is a 5X increase in time taken to complete intel_pstate_set_pstate > while using cpufreq_stats compared to having custom stats exported.
Try calling cpufreq_stat_notifier_trans() directly instead of a notifier and lets see if this makes it any better.
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