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Commit 76d034ed authored by Yuyang Du's avatar Yuyang Du Committed by Ingo Molnar
Browse files

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: default avatarYuyang Du <yuyang.du@intel.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 05296e75

Documentation/scheduler/sched-pelt.c

0 → 100644
+108 −0
Original line number Diff line number Diff line 
/*

 * 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();

}