[V3,3/8] genirq/timings: Optimize the period detection speed

Message ID 20190527205521.12091-4-daniel.lezcano@linaro.org
State Accepted
Commit 3c2e79f4cef7938125b356e7f5c8fd038212619a
Headers show
Series
  • genirq/timings: Fixes and selftests
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Commit Message

Daniel Lezcano May 27, 2019, 8:55 p.m.
If we have 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 our 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>

---
 kernel/irq/timings.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.17.1

Patch

diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c
index 19d2fad379ee..1d1c411d4cae 100644
--- a/kernel/irq/timings.c
+++ b/kernel/irq/timings.c
@@ -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 */