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.
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.
But an API where you "go fishing" and you don't know upfront on a
successful return if you got the data you're interested into sounds
broken to me
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel@xxxxxxxxxxxx | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/
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