From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757353Ab2GKLXs (ORCPT ); Wed, 11 Jul 2012 07:23:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11218 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753804Ab2GKLXq (ORCPT ); Wed, 11 Jul 2012 07:23:46 -0400 Message-ID: <4FFD621D.5090607@redhat.com> Date: Wed, 11 Jul 2012 14:23:09 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Alexander Graf CC: Christian Borntraeger , Raghavendra K T , "H. Peter Anvin" , Thomas Gleixner , Marcelo Tosatti , Ingo Molnar , Rik van Riel , S390 , Carsten Otte , KVM , chegu vinod , "Andrew M. Theurer" , LKML , X86 , Gleb Natapov , linux390@de.ibm.com, Srivatsa Vaddagiri , Joerg Roedel , Christian Ehrhardt , Paul Mackerras , Benjamin Herrenschmidt Subject: Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler References: <20120709062012.24030.37154.sendpatchset@codeblue> <4FFA8E5E.3070108@de.ibm.com> <4FFD422B.9060008@redhat.com> <4FFD52CD.7040403@de.ibm.com> <4FFD5DA3.3010001@redhat.com> <39DA3B9A-87D6-4EA5-B1FF-B6E30733EF7B@suse.de> In-Reply-To: <39DA3B9A-87D6-4EA5-B1FF-B6E30733EF7B@suse.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2012 02:16 PM, Alexander Graf wrote: >> >>> yes the data structure itself seems based on the algorithm >>> and not on arch specific things. That should work. If we move that to common >>> code then s390 will use that scheme automatically for the cases were we call >>> kvm_vcpu_on_spin(). All others archs as well. >> >> ARM doesn't have an instruction for cpu_relax(), so it can't intercept >> it. Given ppc's dislike of overcommit, > > What dislike of overcommit? I understood ppc virtualization is more of the partitioning sort. Perhaps I misunderstood it. But the reliance on device assignment, the restrictions on scheduling, etc. all point to it. > >> and the way it implements cpu_relax() by adjusting hw thread priority, > > Yeah, I don't think we can intercept relaxing. ... and the lack of ability to intercept cpu_relax() ... > It's basically a nop-like instruction that gives hardware hints on its current priorities. That's what x88 PAUSE does. But we can intercept it (and not just any execution - we can restrict intercept to tight loops executed more than a specific number of times). > That said, we can always add PV code. Sure, but that's defeated by advancements like self-tuning PLE exits. It's hard to get this right. -- error compiling committee.c: too many arguments to function