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sched/Documentation: Add 'sched-pelt' tool 

Add a user-space program to compute/generate the PELT constants.

The kernel/sched/sched-pelt.h header will contain the output of
this program.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: matt@codeblueprint.co.uk
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1486935863-25251-2-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
zero-colors
Yuyang Du 2017-02-13 05:44:22 +08:00 committed by Ingo Molnar
parent 05296e7535
commit 76d034edcf
1 changed files with 108 additions and 0 deletions
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108
Documentation/scheduler/sched-pelt.c 100644
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/*
* The following program is used to generate the constants for
* computing sched averages.
*
* ==============================================================
* C program (compile with -lm)
* ==============================================================
*/
#include <math.h>
#include <stdio.h>
#define HALFLIFE 32
#define SHIFT 32
double y;
void calc_runnable_avg_yN_inv(void)
{
int i;
unsigned int x;
printf("static const u32 runnable_avg_yN_inv[] = {");
for (i = 0; i < HALFLIFE; i++) {
x = ((1UL<<32)-1)*pow(y, i);
if (i % 6 == 0) printf("\n\t");
printf("0x%8x, ", x);
}
printf("\n};\n\n");
}
int sum = 1024;
void calc_runnable_avg_yN_sum(void)
{
int i;
printf("static const u32 runnable_avg_yN_sum[] = {\n\t 0,");
for (i = 1; i <= HALFLIFE; i++) {
if (i == 1)
sum *= y;
else
sum = sum*y + 1024*y;
if (i % 11 == 0)
printf("\n\t");
printf("%5d,", sum);
}
printf("\n};\n\n");
}
int n = -1;
/* first period */
long max = 1024;
void calc_converged_max(void)
{
long last = 0, y_inv = ((1UL<<32)-1)*y;
for (; ; n++) {
if (n > -1)
max = ((max*y_inv)>>SHIFT) + 1024;
/*
* This is the same as:
* max = max*y + 1024;
*/
if (last == max)
break;
last = max;
}
n--;
printf("#define LOAD_AVG_PERIOD %d\n", HALFLIFE);
printf("#define LOAD_AVG_MAX %ld\n", max);
// printf("#define LOAD_AVG_MAX_N %d\n\n", n);
}
void calc_accumulated_sum_32(void)
{
int i, x = sum;
printf("static const u32 __accumulated_sum_N32[] = {\n\t 0,");
for (i = 1; i <= n/HALFLIFE+1; i++) {
if (i > 1)
x = x/2 + sum;
if (i % 6 == 0)
printf("\n\t");
printf("%6d,", x);
}
printf("\n};\n\n");
}
void main(void)
{
printf("/* Generated by Documentation/scheduler/sched-pelt; do not modify. */\n\n");
y = pow(0.5, 1/(double)HALFLIFE);
calc_runnable_avg_yN_inv();
// calc_runnable_avg_yN_sum();
calc_converged_max();
// calc_accumulated_sum_32();
}