On Wed, 2008-03-05 at 17:05 -0600, Anthony Liguori wrote: > Dor Laor wrote: > > On Wed, 2008-03-05 at 19:30 +0200, Avi Kivity wrote: > > > >> > >> Playing a movie is better than any benchmark; it reflects actual user > >> experience in a real and important use case. Benchmarks are substitutes > >> for real use cases, not the goal of the optimization. > >> > >> > > > > I forgot to mention that the benchmark is measuring time drift in the > > guest. Playing a movie in winxp changes the guest clock frequency from > > 100HZ to 1000HZ, thus causing a 250HZ host to coalesce pit irqs. > > > > So good pic & pit combination can handle guest multimedia without drifts > > while insufficient implementation just can't. > > > > I'll try out these patches in the next day or so. Is the expectation > that Standard HAL + in-kernel APIC/PIT will have smoother playback than > ACPI HAL w/o in-kernel APIC/PIT? I presume that the ACPI HAL is > unaffected by in-kernel PIT? >
Standard HAL + userspace pic + -tdf option should give no guest time drift (actually sometimes massive correction of irq injection do the opposite, also since time drifts without -dtf it might look better but the movie does not runs in real time). Standard HAL + in-kernel pit patch + in-kernel irqchip should not drift. All other combinations should drift (sometimes you need to overload the cpu to see the drift). As for ACPI hal, the in-kernel apic doesn't drift, it also enable having flex priority or Avi's tpr optimization that boost overall performance. ACPI HAL should not be affected by the in-kernel pit. > Regards, > > Anthony Liguori > > ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
