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 13:56:11 +0200 Message-ID: <4B98DA5B.6040200@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> 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]:35539 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757594Ab0CKL4O (ORCPT ); Thu, 11 Mar 2010 06:56:14 -0500 In-Reply-To: <20100311102303.GD16909@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. -- error compiling committee.c: too many arguments to function