From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH RFC v6 10/11] pvqspinlock, x86: Enable qspinlock PV support for KVM Date: Tue, 18 Mar 2014 09:18:13 +0100 Message-ID: <53280145.5050809@redhat.com> References: <1394650498-30118-1-git-send-email-Waiman.Long@hp.com> <1394650498-30118-11-git-send-email-Waiman.Long@hp.com> <5321B9BE.7050209@redhat.com> <5322035B.5000205@hp.com> <5322C0F7.2090604@redhat.com> <53273532.1010003@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53273532.1010003@hp.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Waiman Long Cc: Jeremy Fitzhardinge , Raghavendra K T , linux-kernel@vger, kvm@vger.kernel.org, Peter Zijlstra , virtualization@lists.linux-foundation.org, Andi Kleen , "H. Peter Anvin" , Michel Lespinasse , Alok Kataria , linux-arch@vger.kernel.org, Gleb Natapov , x86@kernel.org, Ingo Molnar , xen-devel@lists.xenproject.org, "Paul E. McKenney" , Arnd Bergmann , Scott J Norton , Steven Rostedt , Chris Wright , Thomas Gleixner , Aswin Chandramouleeswaran , Chegu Vinod , Boris Ostrovsky , Oleg Nesterov List-Id: linux-arch.vger.kernel.org Il 17/03/2014 18:47, Waiman Long ha scritto: >> Yeah, what I mean is that the patches that enable paravirtualization >> should also take care of decreasing the unfair-lock jump label when >> paravirtualization is enabled. > > As there are people who don't like unfair lock at all, I prefer to give > them the option to turn this on or off instead of forcing them to always > use unfair lock in a PV guest. I understand, but this is virtualization after all. A bad scheduler decision means no progress at all. That's much worse than unfairness. And also, KVM and Xen will stay fair, so if you want fairness just pick a hypervisor that supports it. Paolo