On Tue, Jan 08, 2019 at 11:36:33AM -0500, Boris Ostrovsky wrote: > On 1/8/19 5:48 AM, Peter Zijlstra wrote: > > On the various exclude options; they are as follows (IIUC): > > > > - exclude_guest: we're a HV/host-kernel and we don't want the counter > > to run when we run a guest context. > > > > - exclude_host: we're a HV/host-kernel and we don't want the counter > > to run when we run in host context. > > > > - exclude_hv: we're a guest and don't want the counter to run in HV > > context. > > > > Now, KVM always implies exclude_hv afaict (for guests), I'm not sure > > what, if anything Xen does on x86 (IIRC Brendan Gregg once said perf > > works on Xen) -- nor quite sure who to ask, Boris, Jeurgen? > > perf does work inside guests. > > VPMU is managed by the Xen and it presents to the guest only samples > that are associated with the guest. So from that perspective exclude_hv > doesn't seem to be needed. > > There is a VPMU mode that allows profiling whole system (host and > guests) from dom0, and this where exclude_hv might be useful. But this > mode, ahem, needs some work. Thanks Boris!
