Messages in this thread | | | Date | Tue, 10 May 2016 21:07:24 +0200 | Subject | Re: [PATCH][RFC] cpufreq: intel_pstate: Avoid time-costly synchronization if schedutil is not enabled | From | "Rafael J. Wysocki" <> |
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On Tue, May 10, 2016 at 11:24 AM, <yu.c.chen@intel.com> wrote: > From: Chen Yu <yu.c.chen@intel.com>
First, the subject. It doesn't have anything to do with schedutil, so I'd just use something like "Avoid unnecessary synchronize_sched() during initialization".
> Commit bb6ab52f2bef ("intel_pstate: Do not set utilization update > hook too early") moved the assignment of utilization update hook > from intel_pstate_init_cpu to intel_pstate_set_policy(), however > after moving, we need to leverage synchronize_sched() to deal > with synchronization, which is time-costly because it needs to > wait for all the CPUs to go through a grace period. > > Actuall we don't need to synchronize_sched if schedutil has > not been enabled, which also can address the problem in our case, > thus bypass the synchronize_sched during bootup.
"Actually, the synchronize_sched() is not necessary if the utilization update hook has not been set for the given CPU yet, so make the driver check if that's the case and avoid the synchronize_sched() call in that case."
> Fixes: bb6ab52f2bef "intel_pstate: Do not set utilization update hook too early"
I'm not sure I'd call it a fix, unless there is a significant difference in the system boot time or similar. If that's not the case, this simply is an optimization on top of the above commit.
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