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 23:17:16 +0200 Message-ID: <1204838236.3992.15.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> <47D05A82.304@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: <47D05A82.304@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 Thu, 2008-03-06 at 14:56 -0600, Anthony Liguori wrote: > Avi Kivity wrote: > > > >> The thing I'm trying to get at is a quantitative statement about why > >> moving the pit into the kernel is the right thing. I'll try to give > >> the patches a try myself in the next couple of days. I don't think > >> it's obvious that it's the right thing to do without some sort of > >> benchmark supporting it. > >> > > > > 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 tried out WinXP with the standard HAL and the in-kernel APIC patches. > I did not see any appreciable improvement in multimedia playback (video > or audio). I still get the same amount of jitters. I've tried with and > without -tdf too. > > So far, the smoothest play back I've gotten is using the ACPI HAL. Can > you point to a particular example where you see an improvement? Perhaps > a divx or movie trailer that is better with it than without it? > ACPI HAL should perform good. The in kernel PIT should fix time drift on standard HAL when playing movies (pit freq -> 1000hz) and the host cpu is loaded. If the host is not loaded you might not see the drift. Use kernel build or tgz + taskset to load the cpu. Without the patches in-kernel PIC should time drift and userspace PIC + -tdf shouldn't. As for quality, sometimes when time drifts the movies looks smoother but that's not really the required result. > 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/