From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Hetze Subject: Re: Strange CPU usage pattern in SMP guest Date: Mon, 5 Apr 2010 23:24:50 +0200 Message-ID: <20100405212450.CEE7F30301D3@mail.linux-ag.de> References: <20100321001304.B8EAF30301DA@mail.linux-ag.de> <4BA5F03C.1020900@redhat.com> <20100321120236.55228A0015@mail.linux-ag.de> <4BA60EDC.6080202@redhat.com> <20100321145548.CC027A0015@mail.linux-ag.de> <4BA63892.6090006@redhat.com> <20100322125120.DE032A0015@mail.linux-ag.de> <20100323211808.GA25813@amt.cnet> <20100330082743.49A113030135@mail.linux-ag.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Marcelo Tosatti , Avi Kivity , kvm@vger.kernel.org To: Sebastian Hetze Return-path: Received: from ironport.linux-ag.com ([62.245.157.240]:38309 "EHLO ironport.linux-ag.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756653Ab0DEVYx (ORCPT ); Mon, 5 Apr 2010 17:24:53 -0400 Received: from localhost (mail.linux-ag.de [62.245.157.206]) by mail.linux-ag.de (Postfix) with ESMTP id CEE7F30301D3 for ; Mon, 5 Apr 2010 23:24:50 +0200 (CEST) Content-Disposition: inline In-Reply-To: <20100330082743.49A113030135@mail.linux-ag.de> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Mar 30, 2010 at 10:27:43AM +0200, Sebastian Hetze wrote: > With this patch applied, the system runs without hrtimer messages since > 5 days and the timer iterrupts look fine. > > Actually, when restarting the system with the hrtimer patch applied, > we also changed the BIOS setting to disable Intel SmartStep on the host. > Since there are no hrtimer messages at all, it might be that the SmartStep > CPU frequency adjustment is the real cause for the slow interrupts in > the KVM guest. Anyone else experienced these problems? Back with SmartStep enabled, we get "hrtimer: interrupt took 119986041 ns" so it really looks like this SmartStep feature is the actual cause for the interrupts to be delayed in the first place. The system continues to run correctly so far, so the patch does fix the problems caused by these delayed interrupts. Thanx alot & best regards, Sebastian