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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-04 05:58:22 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-09 17:07:58 +0300
commit08f511fd41c3afe303eb9b41bff0570f7c1b6937 (patch)
tree719b4b878711f8c4312fccb9d479151a817fcbaf /drivers/cpufreq/cpufreq_governor.c
parente6f036571e1f65021a442ec7aad087a6a239ecfb (diff)
downloadlinux-08f511fd41c3afe303eb9b41bff0570f7c1b6937.tar.xz
cpufreq: Reduce cpufreq_update_util() overhead a bit
Use the observation that cpufreq_update_util() is only called by the scheduler with rq->lock held, so the callers of cpufreq_set_update_util_data() can use synchronize_sched() instead of synchronize_rcu() to wait for cpufreq_update_util() to complete. Moreover, if they are updated to do that, rcu_read_(un)lock() calls in cpufreq_update_util() might be replaced with rcu_read_(un)lock_sched(), respectively, but those aren't really necessary, because the scheduler calls that function from RCU-sched read-side critical sections already. In addition to that, if cpufreq_set_update_util_data() checks the func field in the struct update_util_data before setting the per-CPU pointer to it, the data->func check may be dropped from cpufreq_update_util() as well. Make the above changes to reduce the overhead from cpufreq_update_util() in the scheduler paths invoking it and to make the cleanup after removing its callbacks less heavy-weight somewhat. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'drivers/cpufreq/cpufreq_governor.c')
-rw-r--r--drivers/cpufreq/cpufreq_governor.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 70079e21fa2d..db46190bb246 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -280,7 +280,7 @@ static inline void gov_clear_update_util(struct cpufreq_policy *policy)
for_each_cpu(i, policy->cpus)
cpufreq_set_update_util_data(i, NULL);
- synchronize_rcu();
+ synchronize_sched();
}
static void gov_cancel_work(struct cpufreq_policy *policy)