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Rik reports that he sees an increase in CPU use in one benchmark
due to commit 612f1a22f067 "cpuidle: poll_state: Add time limit to
poll_idle()" that caused poll_idle() to call local_clock() in every
iteration of the loop. Utilization increase generally means more
non-idle time with respect to total CPU time (on the average) which
implies reduced CPU frequency.
Doug reports that limiting the rate of local_clock() invocations
in there causes much less power to be drawn during a CPU-intensive
parallel workload (with idle states 1 and 2 disabled to enforce more
state 0 residency).
These two reports together suggest that executing local_clock() on
multiple CPUs in parallel at a high rate may cause chips to get hot
and trigger thermal/power limits on them to kick in, so reduce the
rate of local_clock() invocations in poll_idle() to avoid that issue.
Fixes: 612f1a22f067 "cpuidle: poll_state: Add time limit to poll_idle()"
Reported-by: Rik van Riel <riel@surriel.com>
Reported-by: Doug Smythies <dsmythies@telus.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Rik van Riel <riel@surriel.com>
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If poll_idle() is allowed to spin until need_resched() returns 'true',
it may actually spin for a much longer time than expected by the idle
governor, since set_tsk_need_resched() is not always called by the
timer interrupt handler. If that happens, the CPU may spend much
more time than anticipated in the "polling" state.
To prevent that from happening, limit the time of the spinning loop
in poll_idle().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Doug Smythies <dsmythies@telus.net>
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Make the drivers that want to include the polling state into their
states table initialize it explicitly and drop the initialization of
it (which in fact is conditional, but that is not obvious from the
code) from the core.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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Move the polling state initialization code to a separate file built
conditionally on CONFIG_ARCH_HAS_CPU_RELAX to get rid of the #ifdef
in driver.c.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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