From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: High vm-exit latencies during kvm boot-up/shutdown Date: Wed, 24 Oct 2007 10:37:56 +0200 Message-ID: <471F0464.4000704@siemens.com> References: <471D2D8C.1080202@web.de> <10EA09EFD8728347A513008B6B0DA77A02441127@pdsmsx411.ccr.corp.intel.com> <471D96DC.7070809@web.de> <10EA09EFD8728347A513008B6B0DA77A024414D9@pdsmsx411.ccr.corp.intel.com> <471DBA1A.2080108@web.de> <471DC311.2050003@qumranet.com> <471DF76B.7040001@siemens.com> <471E02F7.6080408@qumranet.com> <471E0818.6060405@siemens.com> <471E1290.2000208@qumranet.com> <471E1A77.90808@siemens.com> <471E1DCD.5040301@qumranet.com> <471E21D7.3000309@siemens.com> <471E238E.6040005@qumranet.com> <471E27B0.1090001@siemens.com> <471E29C5.1060807@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Avi Kivity Return-path: In-Reply-To: <471E29C5.1060807-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Avi Kivity wrote: > Jan Kiszka wrote: >> Avi Kivity wrote: >> >>> Jan Kiszka wrote: >>> >>>> It's both: -rt tests were performed with nosmp (-rt locks up under SMP >>>> here), and the Xenomai tests, including the last instrumentation, ran in >>>> SMP mode. So I tend to exclude SMP effects. >>>> >>>> Do you have some suggestion how to analyse what the guest is executing >>>> while those IRQs are delayed? As I said, I suspect some interaction of >>>> the Bochs BIOS is triggering the effect, because it only shows up (with >>>> a Linux guest) before the BIOS prints the first messages. >>>> >>>> >>> The guest is probably spinning. Can you try modifying >>> user/test/bootstrap.S, around the start label, to look like >>> >>> start: jmp start >>> >>> ? This can then be executed with >>> >>> user/kvmctl user/test/bootstrap user/test/access.flat >>> >> Access flat is not being built here (kvm-48), or I'm pressing the wrong >> button. Forcing it with "make test/access.flat" gives build errors. >> What's the trick? >> >> > > Sorry, it's x86_64 specific. Just pick any other small file, since it > won't be executed anyway, and there are no format requirements. > >>> This will give us something consistent to test. The output of kvm_stat >>> should also be interesting (should show exits and irq_exits advancing at >>> 10K/sec). >>> >> You probably mean with the artificial test, not with qemu/kvm. >> >> > > Yes. > I ran user/kvmctl user/test/bootstrap user/test/smp.flat with the busy loop hacked into bootstrap, but I got no latency spots this time. And what should I look for in the output of kvm_stat? Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/