Re: [libvirt-users] problem when get the vm cpu stat
On 19.04.2013 09:40, Wangkai (Kevin,C) wrote:
Hi all,
I try to get vm cpu stat by function “virDomainGetCPUStats”, when the vm
Cpu usage is 100%, I can see from the vm shell by “top”, when the info
Get by the “virDomainGetCPUStats” show only the “cpu_time” increased,
“user_time” and “system_time” was not changed at all.
Is that correct ? How can I get the vm cpu usage?
nparams = virDomainGetCPUStats(domain, NULL, 0, -1, 1, 0);
virDomainGetCPUStats(domain, params, nparams, -1, 1, 0);
You can gather statistics in similar way that 'top' does. Query current
usage in loops and divide increment by time. Something like:
nparams = virDomainGetCPUStats(domain, NULL, 0, -1, 1, 0);
while (1) {
struct timeval now, then;
int i, j;
gettimeofday(&now, NULL);
virDomainGetCPUStats(domain, params_now, nparams, -1, 1, 0);
/* some sleep, e.g. 500ms */
usleep(5000);
virDomainGetCPUStats(domain, params_then, nparams, -1, 1, 0);
gettimeofday(&then, NULL);
/* find appropriate i and j */
/* virDomainGetCPUStats is returning time in microseconds IIRC */
float usage_in_percent = (params_then[i] - params_now[j]) /
(then.tv_usec - now.tv_usec) / 1000;
printf("%f\n", usage_in_percent);
}