From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: + stupid-hack-to-make-mainline-build.patch added to -mm tree Date: Wed, 07 Mar 2007 08:48:36 +0100 Message-ID: <1173253716.24738.540.camel@localhost.localdomain> References: <200703060654.l266sVxr014860@shell0.pdx.osdl.net> <45ED16D2.3000202@vmware.com> <20070306084258.GA15745@elte.hu> <20070306084647.GA16280@elte.hu> <45ED2C82.3080008@vmware.com> <1173178774.24738.311.camel@localhost.localdomain> <45EDD82F.90204@vmware.com> <1173225182.24738.507.camel@localhost.localdomain> <45EE0A68.6010406@vmware.com> <1173230571.24738.534.camel@localhost.localdomain> <45EE190E.4060904@vmware.com> Reply-To: tglx@linutronix.de Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <45EE190E.4060904@vmware.com> Sender: linux-kernel-owner@vger.kernel.org To: Dan Hecht Cc: Zachary Amsden , Ingo Molnar , akpm@linux-foundation.org, ak@suse.de, Virtualization Mailing List , Jeremy Fitzhardinge , Rusty Russell , LKML , john stultz List-Id: virtualization@lists.linuxfoundation.org On Tue, 2007-03-06 at 17:44 -0800, Dan Hecht wrote: > >>> 2) As I said above. The time accounting for virtualization needs to be > >>> fixed in a generic way. > >>> > >>> I'm not going to accept some weird hackery for virtualization, which is > >>> of exactly ZERO value for the kernel itself. Quite the contrary it will > >>> make the cleanup harder and introduce another hard to remove thing, > >>> which will in the worst case last for ever. > >>> > >> Okay, to confirm I'm on the same page as you, you want to move process > >> time accounting from being periodic sampled based to being trace based? > >> i.e. at the system-call/interrupt boundaries, read clocksource and > >> compute directly the amount of system/user/process time? > > > > At least for the paravirt guests this is the correct approach. Once the > > CPU vendors come up with a sane solution for a reliable and fast clock > > source we might use that on real hardware as well. > > > > I thought your preference was to not do things differently from real > hardware? I guess this case you are okay with since you'd like to see > the real hardware case follow eventually? Real hardware _IS_ broken and slow. If we add the facilities for virtualization we want it in a way, which is usable by real hardware as well. > > Yes, with todays hardware it is simply a PITA. PowerPC has some basic > > support for this though, IIRC. > > > > I think S390 maybe too. One more reason to make it a generic solution rather than some extra hackery. tglx