From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: Re: [PATCH 0/6] In kernel PIT patch Date: Thu, 06 Mar 2008 01:24:26 +0200 Message-ID: <1204759466.4708.33.camel@localhost.localdomain> References: <200803041822.40285.sheng.yang@intel.com> <47CD7038.6000200@codemonkey.ws> <1204672734.25172.24.camel@localhost.localdomain> <47CDEE50.3060206@codemonkey.ws> <1204712042.31109.23.camel@localhost.localdomain> <47CEB519.6080305@codemonkey.ws> <47CED8AD.80201@qumranet.com> <1204756823.4708.17.camel@localhost.localdomain> <47CF2723.8070200@codemonkey.ws> Reply-To: dor.laor@qumranet.com Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, Avi Kivity To: Anthony Liguori Return-path: In-Reply-To: <47CF2723.8070200@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org 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/