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Date: Fri, 5 Aug 2016 14:34:00 +0800 From: Leo Yan <leo.yan@...aro.org> To: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org Cc: Leo Yan <leo.yan@...aro.org> Subject: [PATCH] sched/fair: refine maximum periods for decay_load In current code, decay_load() will consider to set load value to zero after passing 32*64 ms. So this means max_load * (0.5^64) ~= 0. Kernel can support maximum number of processes and threads to 2^29 and set task with highest priority with nice=-20 (weight = 88761). So in worst case, one CPU may have maximum load value is: max_load = 2^29 * 88761 < 2^46 In theory after pass 46 periods we can ensure load value will be decayed to zero. So this patch is to change maximum periods from 64 to 48. Signed-off-by: Leo Yan <leo.yan@...aro.org> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e342159..55cb134 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2622,7 +2622,7 @@ static __always_inline u64 decay_load(u64 val, u64 n) if (!n) return val; - else if (unlikely(n > LOAD_AVG_PERIOD * 63)) + else if (unlikely(n > LOAD_AVG_PERIOD * 47)) return 0; /* after bounds checking we can collapse to 32-bit */ -- 1.9.1
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