From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Make QEmu HPET disabled by default for KVM? Date: Thu, 11 Mar 2010 13:56:33 +0200 Message-ID: <4B98DA71.1000305@redhat.com> References: <201003111552.54293.sheng@linux.intel.com> <4B98A99C.8020909@redhat.com> <20100311083157.GZ16909@redhat.com> <201003111638.48661.sheng@linux.intel.com> <20100311084252.GA16909@redhat.com> <4B98ADCE.5060206@redhat.com> <20100311102303.GD16909@redhat.com> <4B98DA5B.6040200@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Sheng Yang , Marcelo Tosatti , kvm@vger.kernel.org To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:55302 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757610Ab0CKL4f (ORCPT ); Thu, 11 Mar 2010 06:56:35 -0500 In-Reply-To: <4B98DA5B.6040200@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/11/2010 01:56 PM, Avi Kivity wrote: > On 03/11/2010 12:23 PM, Gleb Natapov wrote: >>>> >>>> If the problem it due to lost ticks reinjection may solve it, but >>>> only partially. >>>> What if IO thread haven't run even once during the time vcpu did clock >>>> source check? IIRC sometimes we trigger this even with in kernel PIT. >>> That is true. Reinjection can correct problems in the long term, >>> but may fail in the short term. 10 ticks is easily short term in a >>> heavily loaded system. >>> >>> How does it happen with kernel PIT? I could understand it if we had >>> a work item doing the injection, but everything happens either from >>> hrtimer context or vcpu context. >>> >> Do we kick vcpu out of guest mode when hrtimer triggers? I don't see >> us doing it in >> __kvm_timer_fn(). >> > > We're always running on the same cpu as vcpu 0, so no need. > Would be better to do it, though, in case we have migration races. -- error compiling committee.c: too many arguments to function