From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752694AbcF1N6I (ORCPT ); Tue, 28 Jun 2016 09:58:08 -0400 Received: from smtprelay0069.hostedemail.com ([216.40.44.69]:51707 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752595AbcF1N6G (ORCPT ); Tue, 28 Jun 2016 09:58:06 -0400 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2194:2199:2393:2553:2559:2562:3138:3139:3140:3141:3142:3353:3622:3865:3866:3867:3868:3871:3872:3873:3874:5007:6261:7875:7903:8603:9040:9108:10004:10400:10848:10967:11026:11232:11658:11914:12517:12519:12663:12740:13069:13311:13357:13439:13618:14096:14097:14180:14181:14659:14721:21080:30041:30054:30075:30083:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:1,LUA_SUMMARY:none X-HE-Tag: spot31_243ac26ab0938 X-Filterd-Recvd-Size: 2395 Date: Tue, 28 Jun 2016 09:57:27 -0400 From: Steven Rostedt To: Namhyung Kim Cc: kvm@vger.kernel.org, "linux-kernel@vger.kernel.org" , Minchan Kim Subject: Re: [QUESTION] Is there a better way to get ftrace dump on guest? Message-ID: <20160628095727.436925cb@gandalf.local.home> In-Reply-To: References: <20160628062514.GA4674@danjae.aot.lge.com> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Jun 2016 15:33:18 +0900 Namhyung Kim wrote: > Send again to correct addresses, sorry! > > On Tue, Jun 28, 2016 at 3:25 PM, Namhyung Kim wrote: > > Hello, > > > > I'm running some guest machines for kernel development. For debugging > > purpose, I use lots of trace_printk() since it's faster than normal > > printk(). When kernel crash happens the trace buffer is printed on > > console (I set ftrace_dump_on_oops) but it takes too much time. I > > don't want to reduce the size of ring buffer as I want to collect the > > debug info as much as possible. And I also want to see trace from all > > cpu so 'ftrace_dump_on_oop = 2' is not an option. > > > > I know the kexec/kdump (and the crash tool) can dump and analyze the > > trace buffer later. But it's cumbersome to do it everytime and more > > importantly, I don't want to spend the memory for the crashkernel. > > > > So what is the best way to handle this? I'd like to know how others > > setup the debugging environment.. Heh, I'd say something helpful but you basically already shot down all of my advice, because what I do is... 1) Reduce the size of the ring buffer 2) Dump out just one CPU 3) use kexec/kdump and make a crash kernel to extract trace.dat from That's my debugging environment, but it looks like you want something else. -- Steve