Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753963Ab1FSNAk (ORCPT ); Sun, 19 Jun 2011 09:00:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19546 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753614Ab1FSNAi (ORCPT ); Sun, 19 Jun 2011 09:00:38 -0400 Date: Sun, 19 Jun 2011 15:59:56 +0300 From: Gleb Natapov To: Avi Kivity Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Rik van Riel , Jeremy Fitzhardinge , Peter Zijlstra , Anthony Liguori , Eric B Munson Subject: Re: [PATCH 3/7] KVM-HV: KVM Steal time implementation Message-ID: <20110619125956.GV491@redhat.com> References: <1308007897-17013-1-git-send-email-glommer@redhat.com> <1308007897-17013-4-git-send-email-glommer@redhat.com> <20110614074500.GM491@redhat.com> <4DF8226B.20408@redhat.com> <20110615090951.GQ491@redhat.com> <4DFDED2E.6030009@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DFDED2E.6030009@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1652 Lines: 41 On Sun, Jun 19, 2011 at 03:35:58PM +0300, Avi Kivity wrote: > On 06/15/2011 12:09 PM, Gleb Natapov wrote: > >> > >> Actually, I'd expect most read/writes to benefit from caching, no? > >> So why don't we just rename kvm_write_guest_cached() to > >> kvm_write_guest(), and the few places - if any - that need to force > >> transversing of the gfn mappings, get renamed to > >> kvm_write_guest_uncached ? > >> > >Good idea. I do not see any places where kvm_write_guest_uncached is > >needed from a brief look. Avi? > > > > kvm_write_guest_cached() needs something to supply the cache, and > needs recurring writes to the same location. Neither of these are > common (for example, instruction emulation doesn't have either). > Correct. Missed that. So what about changing steal time to use kvm_write_guest_cached()? > >> > >> If done like you said, time spent on the hypervisor is accounted as > >> steal time. I don't think it is. > >I thought that this is the point of a steal time. Running other > >tasks/guests is a hypervisor overhead too after all :) Also what about > >time spend serving host interrupts between put/get? It will not be > >accounted as steal time, correct? > > With accurate interrupt time accounting, it should be. Otherwise > general hypervisor overhead is not steal time. > > (i.e. if the host is not overcommitted, steal time should be close to zero). > -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/