On Sun, Aug 29, 2010 at 12:59:36PM +0300, Avi Kivity wrote: > On 08/26/2010 12:43 AM, Glauber Costa wrote: > >This patch proposes a common steal time implementation. When no > >steal time is accounted, we just add a branch to the current > >accounting code, that shouldn't add much overhead. > > > >When we do want to register steal time, we proceed as following: > >- if we would account user or system time in this tick, and there is > > out-of-cpu time registered, we skip it altogether, and account steal > > time only. > >- if we would account user or system time in this tick, and we got the > > cpu for the whole slice, we proceed normaly. > >- if we are idle in this tick, we flush out-of-cpu time to give it the > > chance to update whatever last-measure internal variable it may have. > > > >This approach is simple, but proved to work well for my test scenarios. > >in a UP guest on UP host, with a cpu-hog in both guest and host shows > >~ 50 % steal time. steal time is also accounted proportionally, if > >nice values are given to the host cpu-hog. > > > >A cpu-hog in the host with no load in the guest, produces 0 % steal time, > >with 100 % idle, as one would expect. > > > > The scheduler people and lkml need to be copied on this patch. > > Since s390 does steal time (I think?), can this code be shared? AFAIK, s390 enables CONFIG_VIRT_CPU_ACCOUNTING, so all timings comes from the hypervisor, and statistical sampling is not involved. We could do that, if our hardware had any method to say precisely how much time we spent in each state, which I don't think we do. So in a summary, s390 is in a totally different ifdef side. Who should we copy at the scheduler side? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
