Re: [libvirt] [PATCHv2 1/2] Add a new flag VIR_DOMAIN_CPU_STATS_VCPU to virDomainGetCPUStats
On Wed, May 02, 2012 at 01:43:03PM -0600, Eric Blake wrote:
On 04/24/2012 03:20 AM, Hu Tao wrote:
> Currently virDomainGetCPUStats gets total cpu usage, which consists
> of:
>
> 1. vcpu usage: the physical cpu time consumed by virtual cpu(s) of
> domain
> 2. hypervisor: `total cpu usage' - `vcpu usage'
>
> The flag VIR_DOMAIN_CPU_STATS_VCPU is for getting vcpu usages.
> ---
> include/libvirt/libvirt.h.in | 8 ++++++++
> src/libvirt.c | 9 +++++++--
> tools/virsh.c | 16 +++++++++++-----
> 3 files changed, 26 insertions(+), 7 deletions(-)
Question: is it better to make the user call virDomainGetCPUStats twice
(once for total with flags==0, once for vcpu with flags=VCPU), where
there is a race between the two calls? Or should we instead return both
As Richard said, we already have had many two-stage-call APIs: one for
the size, another for the result. Do we also face the same race there?
Anyway, this is another story.
counts in the same call, by having two separate virTypedParameter
stat
names and no flag?
In other words, I'm thinking it might be better to keep "cpu_time"
(VIR_DOMAIN_CPU_STATS_CPUTIME) as the first stat, and add a second stat
"vcpu_time" (VIR_DOMAIN_CPU_STATS_VCPUTIME) as a second stat, all within
the same call, with no need to add a flag.
But I like this way because it seems more natural. See v4.
--
Thanks,
Hu Tao