On 05/18/2015 08:13 PM, Marcelo Tosatti wrote: > GOn Mon, May 18, 2015 at 07:45:41PM -0400, Sasha Levin wrote: >> > On 05/18/2015 06:39 PM, Marcelo Tosatti wrote: >>> > > On Tue, May 12, 2015 at 07:17:24PM -0400, Sasha Levin wrote: >>>> > >> Hi all, >>>> > >> >>>> > >> I'm seeing odd jump in time values during boot of a KVM guest: >>>> > >> >>>> > >> [...] >>>> > >> [ 0.000000] tsc: Detected 2260.998 MHz processor >>>> > >> [3376355.247558] Calibrating delay loop (skipped) preset value.. >>>> > >> [...] >>>> > >> >>>> > >> I've bisected it to: >>> > > >>> > > Paolo, Sasha, >>> > > >>> > > Although this might seem undesirable, there is no requirement >>> > > for sched_clock to initialize at 0: >>> > > >>> > > " >>> > > * >>> > > * There is no strict promise about the base, although it tends to start >>> > > * at 0 on boot (but people really shouldn't rely on that). >>> > > * >>> > > " >>> > > >>> > > Sasha, are you seeing any problem other than the apparent time jump? >> > >> > Nope, but I've looked at it again and it seems that it jumps to the host's >> > clock (that is, in the example above the 3376355 value was the host's clock >> > value). >> > >> > >> > Thanks, >> > Sasha > Sasha, thats right. Its the host monotonic clock. It's worth figuring out if (what) userspace breaks on that. I know it says that you shouldn't rely on that, but I'd happily place a bet on at least one userspace treating it as "seconds since boot" or something similar. Thanks, Sasha -- 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
