From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Strange CPU usage pattern in SMP guest Date: Sun, 21 Mar 2010 17:17:38 +0200 Message-ID: <4BA63892.6090006@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Marcelo Tosatti To: Sebastian Hetze Return-path: Received: from mx1.redhat.com ([209.132.183.28]:16822 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753290Ab0CUPRn (ORCPT ); Sun, 21 Mar 2010 11:17:43 -0400 In-Reply-To: <20100321145548.CC027A0015@mail.linux-ag.de> Sender: kvm-owner@vger.kernel.org List-ID: On 03/21/2010 04:55 PM, Sebastian Hetze wrote: > On Sun, Mar 21, 2010 at 02:19:40PM +0200, Avi Kivity wrote: > >> On 03/21/2010 02:02 PM, Sebastian Hetze wrote: >> >>> 12:46:02 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle >>> 12:46:03 all 0,20 11,35 10,96 8,96 0,40 2,99 0,00 0,00 65,14 >>> 12:46:03 0 1,00 11,00 7,00 15,00 0,00 1,00 0,00 0,00 65,00 >>> 12:46:03 1 0,00 7,14 2,04 6,12 1,02 11,22 0,00 0,00 72,45 >>> 12:46:03 2 0,00 15,00 1,00 12,00 0,00 1,00 0,00 0,00 71,00 >>> 12:46:03 3 0,00 11,00 23,00 8,00 0,00 0,00 0,00 0,00 58,00 >>> 12:46:03 4 0,00 0,00 50,00 0,00 0,00 0,00 0,00 0,00 50,00 >>> 12:46:03 5 0,00 13,00 20,00 4,00 0,00 1,00 0,00 0,00 62,00 >>> >>> So it is only CPU4 that is showing this strange behaviour. >>> >>> >> Can you adjust irqtop to only count cpu4? or even just post a few 'cat >> /proc/interrupts' from that guest. >> >> Most likely the timer interrupt for cpu4 died. >> > I've added two keys +/- to your irqtop to focus up and down > in the row of available CPUs. > The irqtop for CPU4 shows a constant number of 6 local timer interrupts > per update, while the other CPUs show various higher values: > > irqtop for cpu 4 > > eth0 188 > Rescheduling interrupts 162 > Local timer interrupts 6 > ata_piix 3 > TLB shootdowns 1 > Spurious interrupts 0 > Machine check exceptions 0 > > > irqtop for cpu 5 > > eth0 257 > Local timer interrupts 251 > Rescheduling interrupts 237 > Spurious interrupts 0 > Machine check exceptions 0 > > So the timer interrupt for cpu4 is not completely dead but somehow > broken. That is incredibly weird. > What can cause this problem? Any way to speed it up again? > The host has 8 cpus and is only running this 6 vcpu guest, yes? Can you confirm the other vcpus are ticking at 250 Hz? What does 'top' show running on cpu 4? Pressing 'f' 'j' will add a last-used-cpu field in the display. Marcelo, any ideas? -- error compiling committee.c: too many arguments to function