From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: High vm-exit latencies during kvm boot-up/shutdown Date: Tue, 23 Oct 2007 18:38:38 +0200 Message-ID: <471E238E.6040005@qumranet.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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Jan Kiszka Return-path: In-Reply-To: <471E21D7.3000309-kv7WeFo6aLtBDgjK7y7TUQ@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 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 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). (once Linux starts executing, it takes a lot of pagefault exits for the mmu, and then a lot of hlt exit once it idles). -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- 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/