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From: Ganesh Mahendran <opensource.ganesh@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@redhat.com, peterz@infradead.org, stable@vger.kernel.org,
	Ganesh Mahendran <opensource.ganesh@gmail.com>
Subject: [PATCH] sched/fair: fix contribution calculation
Date: Wed,  5 Jul 2017 16:46:30 +0800	[thread overview]
Message-ID: <1499244390-4406-1-git-send-email-opensource.ganesh@gmail.com> (raw)

Function __compute_runnable_contrib() is to calculate:
   \Sum 1024*y^n {for (1..n_period)}
But LOAD_AVG_MAX returns sum of 1024*y^n (0..n_period).
So we need to subtract 1024*y^0.

Cc: stable@vger.kernel.org
Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
---
 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 90e26b1..777ad49 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2508,7 +2508,7 @@ static u32 __compute_runnable_contrib(u64 n)
 	if (likely(n <= LOAD_AVG_PERIOD))
 		return runnable_avg_yN_sum[n];
 	else if (unlikely(n >= LOAD_AVG_MAX_N))
-		return LOAD_AVG_MAX;
+		return LOAD_AVG_MAX - 1024;
 
 	/* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
 	do {
-- 
1.9.1

             reply	other threads:[~2017-07-05  8:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-05  8:46 Ganesh Mahendran [this message]
2017-07-05 11:59 ` [PATCH] sched/fair: fix contribution calculation Peter Zijlstra
2017-07-06  1:39   ` Ganesh Mahendran

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