diff mbox

[3/4] sched/fair: Modify accumulated sums for load/util averages

Message ID 570BDB5C.3000608@arm.com
State New
Headers show

Commit Message

Dietmar Eggemann April 11, 2016, 5:14 p.m. UTC 
On 10/04/16 23:36, Yuyang Du wrote:
> After we dropped the incomplete period, the current period should be

> a complete "past" period, since all period boundaries, in the past

> or in the future, are predetermined.

> 

> With incomplete current period:

> 

>          |    |    |    |    |

>        -------------------*

>                         ^ ^

>                         | |

>                       current

> 

> With this patch:

> 

>          |    |    |    |    |

>        -------------------*

>                    ^    ^

>                    |    |

>                    current

> 

> So, the precomputed sums in __accumulated_sum_N[] and

> __accumulated_sum_N32[] should be updated accordingly.

> 

> Update the script to generate the constants:

> 

> print " #:      inv_N    sum_N"

> print "-----------------------"

> y = (0.5)**(1/32.0)

> x = 2**32

> xx = 1024

> for i in range(0, 32):

> 	if i == 0:

> 		x = x-1

> 	else:

> 		x = x*y

> 		xx = int(xx*y + 1024)

> 	print "%2d: %#x %8d" % (i, int(x), int(xx))

>


So since with this patch series, we always operate on period boundaries
you want to add 1024 instead of 1024*y (1024 * 0.5^(1/32) = 1002) for
the most recent period in the past?

Paul Turner's pelt program could be adapted like this:


to achieve this.

$ ./pelt

sum y^n
      exact     *floor*    error
 1:     1024      1024        0
 2:     2026      2026       -0
...
31:    23371     23360      -11
32:    23894     23883      -11

> print " #:  sum_N32"

> print "------------"

> xxx = xx

> for i in range(0, 11):

> 	if i == 0:

> 		xxx = xx

> 	else:

> 		xxx = xxx/2 + xx

> 	print "%2d: %8d" % (i, xxx)

> 

> Signed-off-by: Yuyang Du <yuyang.du@intel.com>

> ---

>  kernel/sched/fair.c | 12 ++++++------

>  1 file changed, 6 insertions(+), 6 deletions(-)

> 

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c

> index 68273e8..49e9f1a 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 */

>  

>  /* Give new sched_entity start runnable values to heavy its load in infant time */

>  void init_entity_runnable_average(struct sched_entity *se)

> @@ -2591,9 +2591,9 @@ static const u32 __decay_inv_multiply_N[] = {

>   * over-estimates when re-combining.

>   */

>  static const u32 __accumulated_sum_N[] = {

> -	    0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,

> -	 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,

> -	17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,

> +	    0, 1024, 2026, 3006, 3965, 4904, 5822, 6721, 7600, 8461, 9303,

> +	10127,10933,11722,12494,13250,13990,14714,15422,16115,16793,17457,

> +	18106,18742,19364,19973,20569,21152,21722,22280,22826,23360,23883,

>  };

>  

>  /*

> @@ -2601,8 +2601,8 @@ static const u32 __accumulated_sum_N[] = {

>   * lower integers.

>   */

>  static const u32 __accumulated_sum_N32[] = {

> -	    0, 23371, 35056, 40899, 43820, 45281,

> -	46011, 46376, 46559, 46650, 46696, 46719,

> +	    0, 23883, 35824, 41795, 44780, 46273,

> +	47019, 47392, 47579, 47672, 47719, 47742,

>  };

>  

>  /*

>
diff mbox

Patch

diff --git a/pelt.c b/pelt.c
index b36194e8bb9c..3c6b42e88c2d 100644
--- a/pelt.c
+++ b/pelt.c
@@ -39,8 +39,8 @@  void calc_yn_sum(int n)
        printf("sum y^n\n");
        printf("   %8s  %8s %8s\n", "exact", "floor", "error");
        for (i = 1; i <= n; i++) {
-               sum = (y * sum + y * 1024);
-               sum_fl = floor(y * sum_fl+ y * 1024);
+               sum = (y * sum + 1024);
+               sum_fl = floor(y * sum_fl + 1024);
                printf("%2d: %8.0f  %8.0f %8.0f\n", i, sum, sum_fl,
                        sum_fl - sum);
        }