Date: Thu, 10 Oct 2002 01:15:24 -0700 (PDT) From: Jian Tang <t_fisher@163.com> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/43887: abnormal CPU useage when use pthread_mutex Message-ID: <200210100815.g9A8FOh8004682@www.freebsd.org>
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>Number: 43887
>Category: kern
>Synopsis: abnormal CPU useage when use pthread_mutex
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Oct 10 01:20:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Jian Tang
>Release: FreeBSD 4.3
>Organization:
CongXing
>Environment:
$ uname -a
FreeBSD cvs.risson.com 4.3-RELEASE FreeBSD 4.3-RELEASE #0: Tue Nov 6 12:53:47 CST 2001 tang@cvs.risson.com:/usr/src/sys
/compile/kernel i386
>Description:
I have a small code to test the efficiency of the pthread_mutext.
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
int main(int argc,char** argv)
{
pthread_mutex_t mutex;
long i,j;
j =0;
pthread_mutex_init(&mutex,NULL);
while(1)
{
pthread_mutex_lock(&mutex);
i = j*j;
j++;
pthread_mutex_unlock(&mutex);
printf("i=%ld\n",i);
if(usleep(800)== -1)
printf("usleep fail. %s",strerror(errno));
}
return 0;
}
When I ran this program, I found that the usage of CPU is very high.
CPU states: 25.3% user, 0.0% nice, 71.6% system, 0.4% interrupt, 2.7% idle
To reduce the usage of CPU,I added the time of usleep. I found that when the time of usleep is large than 1000,the status of cpu came back normal.
CPU states: 0.0% user, 0.0% nice, 1.6% system, 0.4% interrupt, 98.1% idle
I guess this problem is caused by the scheduler of thread.
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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