* [PATCH] sched/fair: fix contribution calculation
@ 2017-07-05 8:46 Ganesh Mahendran
2017-07-05 11:59 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: Ganesh Mahendran @ 2017-07-05 8:46 UTC (permalink / raw)
To: linux-kernel; +Cc: mingo, peterz, stable, Ganesh Mahendran
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
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] sched/fair: fix contribution calculation
2017-07-05 8:46 [PATCH] sched/fair: fix contribution calculation Ganesh Mahendran
@ 2017-07-05 11:59 ` Peter Zijlstra
2017-07-06 1:39 ` Ganesh Mahendran
0 siblings, 1 reply; 3+ messages in thread
From: Peter Zijlstra @ 2017-07-05 11:59 UTC (permalink / raw)
To: Ganesh Mahendran; +Cc: linux-kernel, mingo, stable
On Wed, Jul 05, 2017 at 04:46:30PM +0800, Ganesh Mahendran wrote:
> 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 {
This code no longer exists...
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] sched/fair: fix contribution calculation
2017-07-05 11:59 ` Peter Zijlstra
@ 2017-07-06 1:39 ` Ganesh Mahendran
0 siblings, 0 replies; 3+ messages in thread
From: Ganesh Mahendran @ 2017-07-06 1:39 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: linux-kernel, mingo, stable
Hello, Peter:
2017-07-05 19:59 GMT+08:00 Peter Zijlstra <peterz@infradead.org>:
> On Wed, Jul 05, 2017 at 04:46:30PM +0800, Ganesh Mahendran wrote:
>> 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 {
>
>
> This code no longer exists...
Yes, you are right. The latest kernel has fix this.
Do we need to fix this in LTS 4.1, 4.4?
Thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-07-05 8:46 [PATCH] sched/fair: fix contribution calculation Ganesh Mahendran
2017-07-05 11:59 ` Peter Zijlstra
2017-07-06 1:39 ` Ganesh Mahendran
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