Re: [libvirt] [PATCH 1/8] qemu: bulk stats: extend internal collection API

----- Original Message ----- > From: "Peter Krempa" <pkrempa(a)redhat.com&gt; > To: "Francesco Romani" <fromani(a)redhat.com&gt;, libvir-list(a)redhat.com > Sent: Wednesday, September 10, 2014 10:07:33 AM > Subject: Re: [libvirt] [PATCH 1/8] qemu: bulk stats: extend internal collection API [...] >>> Hmm this skips offline domains entirely if one of the stats groups needs >>> the monitor. >>> >>> I think we should rather skip individual stats groups, or better stats >>> fields that we can't provide. >>> >>> Any ideas? >> >> What about this (pseudo-C): >> >> unsigned int privflags = 0; >> >> if (needmon && qemuDomainObjBeginJob(driver, dom, QEMU_JOB_QUERY) >> needmon = false; >> /* auto disable monitoring, the remainder of the function should be >> unchanged */ >> else >> privflags |= MONITOR_AVAILABLE; >> >> if ((needmon && virDomainObjIsActive(dom)) || !needmon) {

>> if (qemuDomainGetStats(conn, dom, stats, &tmp, privflags) < 0)

>> /* pass monitor availability down the chain. Individual workers >> will >> bail out immediately and silently if they need monitor but >> it is >> not available >> */ >> goto endjob; >> >> if (tmp) >> tmpstats[nstats++] = tmp; >> } >> >> >> No other change should be needed to this patch, and with trivial changes >> all the others can be fixed. > > Also you can just grab the lock always and the workers will exit if the > VM is not alive. Having a domain job should be fine. As you prefer. For oVirt, we do care of all the stats group implemented, and always all of them, (actually I may have missed some bits, e.g. the pininfo as you pointed out elsewhere - going to fix), so for our needs we'll always need to enter the monitor. But other users of this API may beg to differ, and I believe is fair to assume that other consumers of this API could just use stats which doesn't require to enter the monitor: e.g. CPU/VCPU/interface.

Hence, I was trying to be a good citizen and do not require monitor access unless it is actually needed; but if turns out it is OK to do a domain job anyway, I'll happily simplify my code :) Thanks and bests,