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SubjectRe: [PATCH v1 01/10] sched/fair: Chance LOAD_AVG_MAX_N from 345 to 347
On 10 August 2016 at 02:14, Yuyang Du <yuyang.du@intel.com> wrote:
> In commit 5b51f2f80b3b906ce59bd4dce6eca3c7f34cb1b9
> Author: Paul Turner <pjt@google.com>
> Date: Thu Oct 4 13:18:32 2012 +0200
>
> sched: Make __update_entity_runnable_avg() fast
>
> Paul has a program to compute LOAD_AVG_MAX_N, which basically means
> how many periods (at least) are needed for LOAD_AVG_MAX, and the result
> of calc_conv(1024) is 345:
>
> long mult_inv(long c, int n) {
> return (c * runnable_avg_yN_inv[n]) >> WMULT_SHIFT;
> }
>
> void calc_conv(long n) {
> long old_n;
> int i = -1;
>
> printf("convergence (LOAD_AVG_MAX, LOAD_AVG_MAX_N)\n");
> do {
> old_n = n;
> n = mult_inv(n, 1) + 1024;
> i++;
> } while (n != old_n);
> printf("%d> %ld\n", i - 1, n);
> printf("\n");
> }
>
> The initial value of i is -1, which should be 1 as far as I can tell.
> Accordingly, the final result of LOAD_AVG_MAX_N should be changed
> from 345 to 347.
>
> Signed-off-by: Yuyang Du <yuyang.du@intel.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 4088eed..997297b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -666,7 +666,7 @@ static unsigned long task_h_load(struct task_struct *p);
> */
> #define LOAD_AVG_PERIOD 32
> #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
> -#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
> +#define LOAD_AVG_MAX_N 347 /* number of full periods to produce LOAD_AVG_MAX */

Acked-by: Vincent Guittot <vincent.guitto@linar.org>

>
> /* Give new sched_entity start runnable values to heavy its load in infant time */
> void init_entity_runnable_average(struct sched_entity *se)
> --
> 1.7.9.5
>

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