From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] kvm: add flightrecorder script Date: Mon, 12 Mar 2012 14:08:10 +0200 Message-ID: <4F5DE72A.1000103@redhat.com> References: <1331302420-29737-1-git-send-email-stefanha@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Anthony Liguori To: Stefan Hajnoczi Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49975 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753255Ab2CLMIR (ORCPT ); Mon, 12 Mar 2012 08:08:17 -0400 In-Reply-To: <1331302420-29737-1-git-send-email-stefanha@linux.vnet.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/09/2012 04:13 PM, Stefan Hajnoczi wrote: > The kvm kernel module includes a number of trace events which can be > useful when debugging system behavior. Even on production systems these > trace events can be used to observe guest behavior and identify the > source of problems. > > The kvm_flightrecorder script is a command-line wrapper for the > /sys/kernel/debug/tracing interface. Kernel symbols do not need to be > installed. > > This script captures a fixed-size buffer of KVM trace events. Recent > events overwrite the oldest events when the buffer size is exceeded and > it is possible to leave KVM tracing enabled for any period of time with > just a fixed-size buffer. If the buffer is large enough this script is > a useful tool for collecting detailed information after an issue occurs > with a guest. Hence the name "flight recorder". > > The script can also be used in 'tail' mode to simply view KVM trace > events as they occur. This is handy for development and to ensure that > the guest is indeed running. > > Have you considered updating trace-cmd or perf-something instead? While each of these tools are useful we miss out on combining capabilities. For example you could 'perf probe' a dynamic tracepoint and flightrecord it together with kvm tracepoints. -- error compiling committee.c: too many arguments to function