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Commit c0c9e721 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Ingo Molnar
Browse files

perf sched: Fix for getting task's execution time 



In current code, task's execute time is got by reading
'/proc/<pid>/sched' file, it's wrong if the task is created
by pthread_create(), because every thread task has same pid.

This way also has two demerits:

 1: 'perf sched replay' can't work if the kernel is not
    compiled with the 'CONFIG_SCHED_DEBUG' option

 2: perf tool should depend on proc file system

So, this patch uses PERF_COUNT_SW_TASK_CLOCK to get task's
execution time instead of reading /proc file.

Changelog v2 -> v3:
use PERF_COUNT_SW_TASK_CLOCK instead of rusage() as Ingo's
suggestion

Reported-by: default avatarTorok Edwin <edwintorok@gmail.com>
Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Xiao Guangrong <ericxiao.gr@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <4B1F7322.80103@cn.fujitsu.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 822a6961

tools/perf/builtin-sched.c

+27 −28
Original line number Diff line number Diff line
@@ -13,7 +13,6 @@ 
#include "util/debug.h"

#include "util/data_map.h"



#include <sys/types.h>

#include <sys/prctl.h>



#include <semaphore.h>
@@ -414,34 +413,33 @@ static u64 get_cpu_usage_nsec_parent(void) 
	return sum;

}



static u64 get_cpu_usage_nsec_self(void)

static int self_open_counters(void)

{

	char filename [] = "/proc/1234567890/sched";

	unsigned long msecs, nsecs;

	char *line = NULL;

	u64 total = 0;

	size_t len = 0;

	ssize_t chars;

	FILE *file;

	int ret;

	struct perf_event_attr attr;

	int fd;



	sprintf(filename, "/proc/%d/sched", getpid());

	file = fopen(filename, "r");

	BUG_ON(!file);

	memset(&attr, 0, sizeof(attr));



	while ((chars = getline(&line, &len, file)) != -1) {

		ret = sscanf(line, "se.sum_exec_runtime : %ld.%06ld\n",

			&msecs, &nsecs);

		if (ret == 2) {

			total = msecs*1e6 + nsecs;

			break;

		}

	attr.type = PERF_TYPE_SOFTWARE;

	attr.config = PERF_COUNT_SW_TASK_CLOCK;



	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);



	if (fd < 0)

		die("Error: sys_perf_event_open() syscall returned"

		    "with %d (%s)\n", fd, strerror(errno));

	return fd;

}

	if (line)

		free(line);

	fclose(file);



	return total;

static u64 get_cpu_usage_nsec_self(int fd)

{

	u64 runtime;

	int ret;



	ret = read(fd, &runtime, sizeof(runtime));

	BUG_ON(ret != sizeof(runtime));



	return runtime;

}



static void *thread_func(void *ctx)
@@ -450,9 +448,11 @@ static void *thread_func(void *ctx) 
	u64 cpu_usage_0, cpu_usage_1;

	unsigned long i, ret;

	char comm2[22];

	int fd;



	sprintf(comm2, ":%s", this_task->comm);

	prctl(PR_SET_NAME, comm2);

	fd = self_open_counters();



again:

	ret = sem_post(&this_task->ready_for_work);
@@ -462,16 +462,15 @@ again: 
	ret = pthread_mutex_unlock(&start_work_mutex);

	BUG_ON(ret);



	cpu_usage_0 = get_cpu_usage_nsec_self();

	cpu_usage_0 = get_cpu_usage_nsec_self(fd);



	for (i = 0; i < this_task->nr_events; i++) {

		this_task->curr_event = i;

		process_sched_event(this_task, this_task->atoms[i]);

	}



	cpu_usage_1 = get_cpu_usage_nsec_self();

	cpu_usage_1 = get_cpu_usage_nsec_self(fd);

	this_task->cpu_usage = cpu_usage_1 - cpu_usage_0;



	ret = sem_post(&this_task->work_done_sem);

	BUG_ON(ret);