From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] raise tsc clocksource rating Date: Tue, 30 Oct 2007 00:02:13 +0100 Message-ID: <20071029230213.GA1982@elte.hu> References: <11936994092607-git-send-email-gcosta@redhat.com> <1193697734.9793.86.camel@bodhitayantram.eng.vmware.com> <20071029224852.GA27547@elte.hu> <1193698505.9793.90.camel@bodhitayantram.eng.vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Glauber de Oliveira Costa , linux-kernel@vger.kernel.org, tglx@linutronix.de, rusty@rustcorp.com.au, jeremy@goop.org, --cc@redhat.com, avi@quramnet.com, kvm-devel@lists.sourceforge.net, Glauber de Oliveira Costa , Dan Hecht , Garrett Smith To: Zachary Amsden Return-path: Content-Disposition: inline In-Reply-To: <1193698505.9793.90.camel@bodhitayantram.eng.vmware.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org * Zachary Amsden wrote: > On Mon, 2007-10-29 at 23:48 +0100, Ingo Molnar wrote: > > * Zachary Amsden wrote: > > > if it's inaccurate why are you exposing it to the guest then? Native > > only uses the TSC if it's safe and accurate to do so. > > Not every guest support paravirt, but for correctness, all guests > require TSC, which must be exposed all the way up to userspace, no > matter what the efficiency or accuracy may be. but if there's a perfect TSC available (there is such hardware) then the TSC _is_ the best clocksource. Paravirt now turns it off unconditionally in essence. anyway, that's at most an optimization issue. No strong feelings here, and we can certainly delay this patch until this gets all sorted out. Ingo