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| Started by | Yuyang Du <yuyang.du@intel.com> |
|---|---|
| First post | 2016-04-11 08:20 +0200 |
| Last post | 2016-04-11 19:20 +0200 |
| Articles | 2 — 2 participants |
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[PATCH 3/4] sched/fair: Modify accumulated sums for load/util averages Yuyang Du <yuyang.du@intel.com> - 2016-04-11 08:20 +0200
Re: [PATCH 3/4] sched/fair: Modify accumulated sums for load/util averages Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-04-11 19:20 +0200
| From | Yuyang Du <yuyang.du@intel.com> |
|---|---|
| Date | 2016-04-11 08:20 +0200 |
| Subject | [PATCH 3/4] sched/fair: Modify accumulated sums for load/util averages |
| Message-ID | <rmDmy-1gf-7@gated-at.bofh.it> |
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))
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,
};
/*
--
2.1.4
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| From | Dietmar Eggemann <dietmar.eggemann@arm.com> |
|---|---|
| Date | 2016-04-11 19:20 +0200 |
| Subject | Re: [PATCH 3/4] sched/fair: Modify accumulated sums for load/util averages |
| Message-ID | <rmNFf-X9-3@gated-at.bofh.it> |
| In reply to | #1375508 |
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:
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);
}
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,
> };
>
> /*
>
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