Re: [libvirt] [PATCH 1/1] perf: add more perf events support

-----Original Message----- From: libvir-list-bounces(a)redhat.com [mailto:libvir-list-bounces@redhat.com] On Behalf Of Ren, Qiaowei Sent: Sunday, June 12, 2016 10:14 AM To: Peter Krempa <pkrempa(a)redhat.com&gt; Cc: libvir-list(a)redhat.com Subject: Re: [libvirt] [PATCH 1/1] perf: add more perf events support > > diff --git a/include/libvirt/libvirt-domain.h > > b/include/libvirt/libvirt-domain.h > > index cba4fa5..99c4c48 100644 > > --- a/include/libvirt/libvirt-domain.h > > +++ b/include/libvirt/libvirt-domain.h > > @@ -1928,6 +1928,45 @@ void > virDomainStatsRecordListFree(virDomainStatsRecordPtr *stats); > > */ > > # define VIR_PERF_PARAM_MBML "mbml" > > [...] > > > +/** > > + * VIR_PERF_PARAM_INSTRUCTIONS: > > + * > > + * Macro for typed parameter name that represents instructions perf > > + * event which can be used to measure the amount of instructions > > + * by applications running on the platform. It corresponds to the > > + * "perf.instructions" field in the *Stats APIs. > > I'm not sure if I understand the implications and usability of this stat parameter. > Could you elaborate on how this can be used? > > > + */ > > +# define VIR_PERF_PARAM_INSTRUCTIONS "instructions" > > + > > +/** > > + * VIR_PERF_PARAM_CPU_CYCLES: > > + * > > + * Macro for typed parameter name that represents cpu_cycles perf > > +event > > + * which can be used to measure how many cycles one instruction needs. > > + * It corresponds to the "perf.cpu_cycles" field in the *Stats APIs. > > And same for this. I don't really see how this can be used. > Peter, thanks for your feedback! Instructions and cycles can be used to gain IPC (Instructions Per Clock, = Instructions/Cycles), and a low IPC ratio indicates the code of the process makes poor use of the CPU.