On Tue, 19 Apr 2011 12:29:05 +0100
"Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote:
> On Fri, Apr 15, 2011 at 04:43:03PM +0900, KAMEZAWA Hiroyuki wrote:
> > On Fri, 15 Apr 2011 09:43:15 +0200
> > Matthias Bolte <matthias.bolte@xxxxxxxxxxxxxx> wrote:
> >
> > > 2011/4/15 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>:
> > > Also do you really need the absolute CPU time?
> > yes, for virt-top -1.
>
> I don't think that is correct. What virt-top ultimately displays
> to the end user is a % utilization. So it would be happy to get
> data in either % util & display that directly, or get absolute
> CPU time and calculate deltas to display % util.
>
virt-top calculate delta by itself.
> I wonder if we could provide an API that could be used to provide
> either per-VCPU or per-PCPU statistics in one go, so that we
> can finally have an API for cpu time that works well for VMWare.
>
VMWare ?
> eg
>
> typedef struct _virDomainCPUTime virDomainCPUTime;
> typedef virDomainCPUTime *virDomainCPUTimePtr;
>
> #define VIR_DOMAIN_CPUTIME_ABS "abs"
> #define VIR_DOMAIN_CPUTIME_UTIL "util"
> ...define more stats later if desired...
>
To calculate 'util', we need 'interval' for calculating it.
What interval do we use ? The libvirt need to calculate it periodically
by making a thread ?
"util" can be very easily calculated by
util = cpuTime-delta / (interval(sec) * 1000000000) * 100.
So, it depens on interval. For example, when we make fair-share-scheduler's
balancing interval to 1sec, we never want interaval smaller than 1 sec.
IIUC, virt-top users can specify 'interval'. So, virt-top needs to
use absolute cpuTime delta even if libvirt provides 'util'. Because to show
what users want, virt-top needs to use interval users want.
> struct _virDomainCPUTime {
> char field[VIR_DOMAIN_CPU_TIME_FIELD_LENGTH];
> unsigned long long value;
> };
>
> typedef enum {
> VIR_DOMAIN_CPU_TIME_VIRTUAL = 0,
> VIR_DOMAIN_CPU_TIME_PHYSICAL = 1,
> } virDomainCPUTimeFlags;
>
> int virDomainGetCPUTime(virDomainPtr dom,
> virDomainCPUTimePtr stats,
> int *nstats,
> unsigned int flags);
>
>
> When querying per-virtual CPU time, nstats would be the number of
> virtual CPUs in the guest. eg
>
Why we take care of vcpus ?
> virDomainInfo info;
> virDomainGetInfo(dom, &info);
> virDomainCPUTimePtr stats;
>
> stats = malloc(sizeof(*stats)*info.nrVirtCPU);
>
> virDomainGetCPUTime(dom, stats, info.nrVirtCPU,
> VIR_DOMAIN_CPU_TIME_VIRTUAL);
>
>
>
> Or to get the break down per physical CPU, use the VIR_NODEINFO_MAX_CPUS
> macro
>
per vcpu pcpu time is not what I want. Hmm, others needs such information ?
And virt-top need to re-calculate per-vm pcpu time by making sum of cputime per
vcpu on pcus ? Anyway, cpuacct cgroup/ Linux kernel cannot provide per-vcpu-per-pcpu
time and I cannot implement qemu driver.
Thanks,
-Kame
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