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Message-ID: <4AC060AE.1090401@gmail.com>
Date: Mon, 28 Sep 2009 09:07:26 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.32-rc1
Linus Torvalds a écrit :
>
> Go wild, test it out, and let us know about any regressions you find,
>
>
Hi Linus
Something seems wrong with process time accounting.
Following program should consume 10*8 seconds of cpu on a 8 cpu machine, but
with 2.6.32-rc1 numbers are crazy.
$ gcc -O2 -o process process.c -lpthread
$ ./process
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:08 ./process
- - Sl+ 0:00 -
- - Rl+ 0:05 -
- - Rl+ 0:05 -
- - Rl+ 0:09 -
- - Rl+ 0:05 -
- - Rl+ 0:05 -
- - Rl+ 0:05 -
- - Rl+ 0:05 -
- - Rl+ 0:01 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:16 ./process
- - Sl+ 0:00 -
- - Rl+ 0:14 -
- - Rl+ 0:06 -
- - Rl+ 0:14 -
- - Rl+ 0:10 -
- - Rl+ 0:06 -
- - Rl+ 0:06 -
- - Rl+ 0:10 -
- - Rl+ 0:02 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:24 ./process
- - Sl+ 0:00 -
- - Rl+ 0:20 -
- - Rl+ 0:11 -
- - Rl+ 0:24 -
- - Rl+ 0:15 -
- - Rl+ 0:07 -
- - Rl+ 0:07 -
- - Rl+ 0:24 -
- - Rl+ 0:03 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:32 ./process
- - Sl+ 0:00 -
- - Rl+ 0:29 -
- - Rl+ 0:12 -
- - Rl+ 0:29 -
- - Rl+ 0:21 -
- - Rl+ 0:08 -
- - Rl+ 0:08 -
- - Rl+ 0:29 -
- - Rl+ 0:04 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:40 ./process
- - Sl+ 0:00 -
- - Rl+ 0:35 -
- - Rl+ 0:13 -
- - Rl+ 0:35 -
- - Rl+ 0:26 -
- - Rl+ 0:09 -
- - Rl+ 0:09 -
- - Rl+ 0:35 -
- - Rl+ 0:05 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:48 ./process
- - Sl+ 0:00 -
- - Rl+ 0:40 -
- - Rl+ 0:14 -
- - Rl+ 0:40 -
- - Rl+ 0:31 -
- - Rl+ 0:10 -
- - Rl+ 0:10 -
- - Rl+ 0:40 -
- - Rl+ 0:06 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 0:56 ./process
- - Sl+ 0:00 -
- - Rl+ 0:45 -
- - Rl+ 0:15 -
- - Rl+ 0:45 -
- - Rl+ 0:37 -
- - Rl+ 0:11 -
- - Rl+ 0:11 -
- - Rl+ 0:45 -
- - Rl+ 0:07 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 1:05 ./process
- - Sl+ 0:00 -
- - Rl+ 0:51 -
- - Rl+ 0:21 -
- - Rl+ 0:55 -
- - Rl+ 0:46 -
- - Rl+ 0:12 -
- - Rl+ 0:12 -
- - Rl+ 0:59 -
- - Rl+ 0:08 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 1:13 ./process
- - Sl+ 0:00 -
- - Rl+ 0:56 -
- - Rl+ 0:22 -
- - Rl+ 1:00 -
- - Rl+ 0:52 -
- - Rl+ 0:13 -
- - Rl+ 0:13 -
- - Rl+ 1:04 -
- - Rl+ 0:09 -
PID TTY STAT TIME COMMAND
5532 pts/1 - 5:13 ./process
- - S+ 5:13 -
$ cat process.c
#include <pthread.h>
#include <time.h>
#include <stdio.h>
/*
* Burn cpu cycles for about 10 seconds
*/
static void *do_unit(void *arg)
{
time_t t0,t1;
t0 = time(NULL);
do {
t1 = time(NULL);
} while (t1 - t0 <= 10);
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t tids[8];
int i;
char cmd[128];
sprintf(cmd, "ps m -p %d", getpid());
for (i = 0; i < 8 ; i++)
pthread_create(&tids[i], NULL, do_unit, NULL);
for (i = 0; i < 9; i++) {
sleep(1);
system(cmd);
}
for (i = 0; i < 8 ; i++)
pthread_join(tids[i], NULL);
system(cmd);
return 0;
}
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