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Subject[PATCH v2] 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 call getrusage() to get task's execution time instead
of reading /proc file

Reported-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
tools/perf/builtin-sched.c | 46 ++++++++++++++-----------------------------
1 files changed, 15 insertions(+), 31 deletions(-)
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 19f43fa..bd57994 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>
@@ -399,49 +398,34 @@ process_sched_event(struct task_desc *this_task __used, struct sched_atom *atom)
}
}

+static u64 get_sum_time(struct rusage *ru)
+{
+ u64 sum;
+
+ sum = ru->ru_utime.tv_sec*1e9 + ru->ru_utime.tv_usec*1e3;
+ sum += ru->ru_stime.tv_sec*1e9 + ru->ru_stime.tv_usec*1e3;
+ return sum;
+}
+
static u64 get_cpu_usage_nsec_parent(void)
{
struct rusage ru;
- u64 sum;
int err;

err = getrusage(RUSAGE_SELF, &ru);
BUG_ON(err);

- sum = ru.ru_utime.tv_sec*1e9 + ru.ru_utime.tv_usec*1e3;
- sum += ru.ru_stime.tv_sec*1e9 + ru.ru_stime.tv_usec*1e3;
-
- return sum;
+ return get_sum_time(&ru);
}

static u64 get_cpu_usage_nsec_self(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;
-
- sprintf(filename, "/proc/%d/sched", getpid());
- file = fopen(filename, "r");
- BUG_ON(!file);
-
- 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);
+ struct rusage ru;
+ int err;

- return total;
+ err = getrusage(RUSAGE_THREAD, &ru);
+ BUG_ON(err);
+ return get_sum_time(&ru);
}

static void *thread_func(void *ctx)
--
1.6.1.2
--
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