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genirq/timings: Optimize the period detection speed 

With a minimal period and if there is a period which is a multiple of it
but lesser than the max period then it will be detected before and the
minimal period will be never reached.

 1 2 1 2 1 2 1 2 1 2 1 2
 <-----> <-----> <----->
 <-> <-> <-> <-> <-> <->

In that case, the minimum period is 2 and the maximum period is 5. That
means all repeating pattern of 2 will be detected as repeating pattern of
4, it is pointless to go up to 2 when searching for the period as it will
always fail.

Remove one loop iteration by increasing the minimal period to 3.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-4-daniel.lezcano@linaro.org
This commit is contained in:
Daniel Lezcano 2019-05-27 22:55:16 +02:00 committed by Thomas Gleixner
parent 2840eef051
commit 3c2e79f4ce
1 changed files with 1 additions and 1 deletions
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2
kernel/irq/timings.c
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@ -261,7 +261,7 @@ void irq_timings_disable(void)
#define EMA_ALPHA_VAL 64
#define EMA_ALPHA_SHIFT 7
#define PREDICTION_PERIOD_MIN 2
#define PREDICTION_PERIOD_MIN 3
#define PREDICTION_PERIOD_MAX 5
#define PREDICTION_FACTOR 4
#define PREDICTION_MAX 10 /* 2 ^ PREDICTION_MAX useconds */