On Mon, 18 Apr 2011 12:30:45 +0100
"Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote:
> On Sun, Apr 10, 2011 at 12:58:56PM +0800, Daniel Veillard wrote:
> > On Fri, Apr 08, 2011 at 08:33:12PM +0900, Minoru Usui wrote:
> > > virNodeGetCPUTime: Expose new API
> > >
> > > Signed-off-by: Minoru Usui <usui@xxxxxxxxxxxxxxxxx>
> > > ---
> > > include/libvirt/libvirt.h.in | 64 ++++++++++++++++++++++++++++++++++++++++++
> > > src/libvirt_public.syms | 5 +++
> > > 2 files changed, 69 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
> > > index bd36015..154c138 100644
> > > --- a/include/libvirt/libvirt.h.in
> > > +++ b/include/libvirt/libvirt.h.in
> > > @@ -228,6 +228,57 @@ struct _virNodeInfo {
> > > unsigned int threads;/* number of threads per core */
> > > };
> > >
> > > +/**
> > > + * virNodeCpuTime:
> > > + *
> > > + * a virNodeCpuTime is a structure filled by virNodeGetCpuTime() and providing
> > > + * the information for the cpu time of the node.
> > > + */
> > > +
> > > +/**
> > > + * Cpu Time Statistics Tags:
> > > + */
> > > +typedef enum {
> > > + /*
> > > + * The cumulative CPU time which spends by kernel,
> > > + * when the node booting up.(in nanoseconds).
> > > + */
> > > + VIR_NODE_CPU_TIME_KERNEL = 0,
> > > + /*
> > > + * The cumulative CPU time which spends by user processes,
> > > + * when the node booting up.(in nanoseconds).
> > > + */
> > > + VIR_NODE_CPU_TIME_USER = 1,
> > > + /*
> > > + * The cumulative idle CPU time,
> > > + * when the node booting up.(in nanoseconds).
> > > + */
> > > + VIR_NODE_CPU_TIME_IDLE = 2,
> > > + /*
> > > + * The cumulative I/O wait CPU time,
> > > + * when the node booting up.(in nanoseconds).
> > > + */
> > > + VIR_NODE_CPU_TIME_IOWAIT = 3,
> > > + /*
> > > + * The CPU utilization.
> > > + * The usage value is in percent and 100% represents all CPUs on
> > > + * the server.
> > > + */
> > > + VIR_NODE_CPU_TIME_UTILIZATION = 4,
> > > +
> > > + /*
> > > + * The number of statistics supported by this version of the interface.
> > > + * To add new statistics, add them to the enum and increase this value.
> > > + */
> > > + VIR_NODE_CPU_TIME_NR = 5,
> > > +} virNodeCpuTimeTags;
> > > +
> > > +typedef struct _virNodeCpuTime virNodeCpuTime;
> > > +
> > > +struct _virNodeCpuTime {
> > > + virNodeCpuTimeTags tag;
> > > + unsigned long long val;
> > > +};
> >
> > NACK, the size of an enum is not defined by the C language and
> > hence is compiler dependant. We cannot use it as a component of a
> > structure in the API.
> >
> > > /**
> > > * virDomainSchedParameterType:
> > > @@ -460,6 +511,14 @@ int virDomainMigrateSetMaxSpeed(virDomainPtr domain,
> > > typedef virNodeInfo *virNodeInfoPtr;
> > >
> > > /**
> > > + * virNodeCpuTimePtr:
> > > + *
> > > + * a virNodeCpuTimePtr is a pointer to a virNodeCpuTime structure.
> > > + */
> > > +
> > > +typedef virNodeCpuTime *virNodeCpuTimePtr;
> > > +
> > > +/**
> > > * virConnectFlags
> > > *
> > > * Flags when opening a connection to a hypervisor
> > > @@ -593,6 +652,11 @@ int virNodeGetInfo (virConnectPtr conn,
> > > virNodeInfoPtr info);
> > > char * virConnectGetCapabilities (virConnectPtr conn);
> > >
> > > +int virNodeGetCpuTime (virConnectPtr conn,
> > > + virNodeCpuTimePtr stats,
> > > + unsigned int nr_stats,
> > > + unsigned int flags);
> > > +
> >
> > I don't understand how the API is suppoed to work. Suppose you want
> > the cumulative CPU time, how do you ask for it ? Seems you can't ! You
> > just ask for a big stucture hoping that on return you may find it within
> > the results. That looks broken to me.
>
> This is the same design we've used in the virDomainGetMemoryStats,
> virDomainGetBlkioParameters, virDomainGetSchedularParamters without
> any undue trouble.
Yes.
> >
> > Either you make a simple API giving back an unsigned long long and
> > you use the virNodeCpuTimeTags as the flag value
> >
> > int virNodeGetCpuTime(virConnectPtr conn, unsigned long long *time,
> > unsigned int flags);
> >
> > and the flags indicate the value you're interested into, but in that
> > case you have to ask multiple times. Or you make the VIR_NODE_CPU_TIME_*
> > values a bit field, and you pass an array
> >
> > int virNodeGetCpuTime(virConnectPtr conn,
> > unsigned long long *stats,
> > unsigned int nr_stats,
> > unsigned int flags);
> >
> > where flags is the logical or of the values you are interested into, and
> > the implementation put them in order based on the VIR_NODE_CPU_TIME_*
> > values. But in that case you must fail if one of the statistics is not
> > available.
>
> I think these are worse because you're relying on ordering of values,
> and not all hypervisors will be able to supply all values. In addition
> it makes this stats API completely different to the other stats APIs
> we have.
OK.
I drop v3 design.
Everyone, how about this v2 patch series? Any other opinions?
>
> Daniel
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--
Minoru Usui <usui@xxxxxxxxxxxxxxxxx>
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