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 > counts in the same call, by having two separate virTypedParameter stat > names and no flag? Slightly off-topic ... My opinion on this -- and it applies to many libvirt calls -- is that APIs where you have to call them twice, once to size the result, and a second time to get the result, are obtuse and hard to use. In libguestfs I took the approach that all calls return malloc'd strings, arrays, etc of the right size. The caller has to free the data, but that's the lesser of two evils. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list