Re: [PATCH v2] qemu: bulk stats: implement (cpu) tune group.

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On Fri, Mar 06, 2015 at 15:22:50 +0100, Francesco Romani wrote:
> Management applications, like oVirt, may need to setup cpu quota
> limits to enforce QoS for domains.
> 
> For this purpose, management applications also need to check how
> domains are behaving with respect to CPU quota. This data is available
> using the virDomainGetSchedulerParameters API.
> 
> This patch adds a new group to bulk stats API to obtain the same
> information.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1191428
> ---
>  include/libvirt/libvirt-domain.h |  1 +
>  src/libvirt-domain.c             | 16 ++++++++
>  src/qemu/qemu_driver.c           | 84 ++++++++++++++++++++++++++++++++++++++++
>  tools/virsh-domain-monitor.c     |  7 ++++
>  tools/virsh.pod                  | 10 ++++-
>  5 files changed, 117 insertions(+), 1 deletion(-)
> 
> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> index a9d3efd..a283f93 100644
> --- a/include/libvirt/libvirt-domain.h
> +++ b/include/libvirt/libvirt-domain.h
> @@ -1723,6 +1723,7 @@ typedef enum {
>      VIR_DOMAIN_STATS_VCPU = (1 << 3), /* return domain virtual CPU info */
>      VIR_DOMAIN_STATS_INTERFACE = (1 << 4), /* return domain interfaces info */
>      VIR_DOMAIN_STATS_BLOCK = (1 << 5), /* return domain block info */
> +    VIR_DOMAIN_STATS_TUNE_CPU = (1 << 6), /* return domain CPU tuning info */
>  } virDomainStatsTypes;
>  
>  typedef enum {
> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> index 89d1eab..b451299 100644
> --- a/src/libvirt-domain.c
> +++ b/src/libvirt-domain.c
> @@ -11004,6 +11004,22 @@ virConnectGetDomainCapabilities(virConnectPtr conn,
>   * "block.<num>.physical" - physical size in bytes of the container of the
>   *                          backing image as unsigned long long.
>   *
> + * VIR_DOMAIN_STATS_TUNE_CPU: Return CPU tuning statistics
> + * and usage information.
> + * The typed parameter keys are in this format:
> + * "tune.vcpu.quota" - max allowed bandwidth, in microseconds, as
> + *                     long long integer. -1 means 'infinite'.
> + * "tune.vcpu.period" - timeframe on which the virtual cpu quota is
> + *                      enforced, in microseconds, as unsigned long long.
> + * "tune.emu.quota" - max allowed bandwidth for emulator threads,
> + *                    in microseconds, as long long integer.
> + *                    -1 means 'infinite'.
> + * "tune.emu.period" - timeframe on which the emulator quota is
> + *                     enforced, in microseconds, as unsigned long long.
> + * "tune.cpu.shares" - weight of this domain. This value is meaningful
> + *                     only if compared with the other values of
> + *                     the running domains. Expressed as unsigned long long.
> + *

These options above represent configuration and not any statistic value,
so they won't change unless libvirt is instructed to change them. I
don't think they belong to the stats API.

Additionally libvirt recently added an event to track change of the
tunables. See virConnectDomainEventTunableCallback.

http://libvirt.org/html/libvirt-libvirt-domain.html#virConnectDomainEventTunableCallback
http://libvirt.org/html/libvirt-libvirt-domain.html#VIR_DOMAIN_TUNABLE_CPU_CPU_SHARES
http://libvirt.org/html/libvirt-libvirt-domain.html#VIR_DOMAIN_TUNABLE_CPU_EMULATORPIN 
and so on ...

I think you want to use that event and leave this api for statistics
only.

NACK

Peter

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