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Subject[PATCH v3] 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 not compile
with 'CONFIG_SCHED_DEBUG' option
2: perf tool should depend on proc file system

So, this patch use 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

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
tools/perf/builtin-sched.c | 55 +++++++++++++++++++++----------------------
1 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 19f43fa..b12b23a 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -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;
- }
- }
- if (line)
- free(line);
- fclose(file);
+ attr.type = PERF_TYPE_SOFTWARE;
+ attr.config = PERF_COUNT_SW_TASK_CLOCK;

- return total;
+ 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;
+}
+
+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);

--
1.6.1.2






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