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Commit 4578ee7e authored by Chen Yu's avatar Chen Yu Committed by Rafael J. Wysocki
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intel_pstate: Avoid unnecessary synchronize_sched() during initialization 

Currently, in intel_pstate_clear_update_util_hook(), after
clearing the utilization update hook, we leverage
synchronize_sched() to deal with synchronization, which
is a little bit time-costly because synchronize_sched()
has to wait for all the CPUs to go through a grace period.

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 then.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=116371


Tested-by: default avatarTian Ye <yex.tian@intel.com>
Signed-off-by: default avatarChen Yu <yu.c.chen@intel.com>
[ rjw : Rebase ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent c29af6f1

drivers/cpufreq/intel_pstate.c

+9 −0
Original line number Diff line number Diff line
@@ -168,6 +168,7 @@ struct _pid { 
 * struct cpudata -	Per CPU instance data storage

 * @cpu:		CPU number for this instance data

 * @update_util:	CPUFreq utility callback information

 * @update_util_set:	CPUFreq utility callback is set

 * @pstate:		Stores P state limits for this CPU

 * @vid:		Stores VID limits for this CPU

 * @pid:		Stores PID parameters for this CPU
@@ -187,6 +188,7 @@ struct cpudata { 
	int cpu;



	struct update_util_data update_util;

	bool   update_util_set;



	struct pstate_data pstate;

	struct vid_data vid;
@@ -1417,11 +1419,18 @@ static void intel_pstate_set_update_util_hook(unsigned int cpu_num) 
	cpu->sample.time = 0;

	cpufreq_add_update_util_hook(cpu_num, &cpu->update_util,

				     intel_pstate_update_util);

	cpu->update_util_set = true;

}



static void intel_pstate_clear_update_util_hook(unsigned int cpu)

{

	struct cpudata *cpu_data = all_cpu_data[cpu];



	if (!cpu_data->update_util_set)

		return;



	cpufreq_remove_update_util_hook(cpu);

	cpu_data->update_util_set = false;

	synchronize_sched();

}