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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: Tian Ye <yex.tian@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
[ rjw : Rebase ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
hifive-unleashed-5.1
Chen Yu 2016-05-11 14:33:08 +08:00 committed by Rafael J. Wysocki
parent c29af6f1a4
commit 4578ee7e1d
1 changed files with 9 additions and 0 deletions
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9
drivers/cpufreq/intel_pstate.c
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@ -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();
}