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cpufreq: governor: Reset sample delay in store_sampling_rate()

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If store_sampling_rate() updates the sample delay when the ondemand
governor is in the middle of its high/low dance (OD_SUB_SAMPLE sample
type is set), the governor will still do the bottom half of the
previous sample which may take too much time.

To prevent that from happening, change store_sampling_rate() to always
reset the sample delay to 0 which also is consistent with the new
behavior of cpufreq_governor_limits().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Rafael J. Wysocki 2016-02-15 02:20:11 +01:00
parent 4cccf75557
commit 78347cdb89
1 changed files with 4 additions and 12 deletions
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16
drivers/cpufreq/cpufreq_governor.c
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@ -38,10 +38,6 @@ EXPORT_SYMBOL_GPL(dbs_data_mutex);
* reducing the sampling rate, we need to make the new value effective
* immediately.
*
* On the other hand, if new rate is larger than the old, then we may evaluate
* the load too soon, and it might we worth updating sample_delay_ns then as
* well.
*
* This must be called with dbs_data->mutex held, otherwise traversing
* policy_dbs_list isn't safe.
*/
@ -69,18 +65,14 @@ ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
* really doesn't matter. If the read returns a value that's
* too big, the sample will be skipped, but the next invocation
* of dbs_update_util_handler() (when the update has been
* completed) will take a sample. If the returned value is too
* small, the sample will be taken immediately, but that isn't a
* problem, as we want the new rate to take effect immediately
* anyway.
* completed) will take a sample.
*
* If this runs in parallel with dbs_work_handler(), we may end
* up overwriting the sample_delay_ns value that it has just
* written, but the difference should not be too big and it will
* be corrected next time a sample is taken, so it shouldn't be
* significant.
* written, but it will be corrected next time a sample is
* taken, so it shouldn't be significant.
*/
gov_update_sample_delay(policy_dbs, dbs_data->sampling_rate);
gov_update_sample_delay(policy_dbs, 0);
mutex_unlock(&policy_dbs->timer_mutex);
}