From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756726Ab0CXS1s (ORCPT ); Wed, 24 Mar 2010 14:27:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12642 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756618Ab0CXS1q (ORCPT ); Wed, 24 Mar 2010 14:27:46 -0400 Date: Wed, 24 Mar 2010 15:27:05 -0300 From: Arnaldo Carvalho de Melo To: Avi Kivity Cc: Joerg Roedel , Anthony Liguori , Ingo Molnar , Pekka Enberg , "Zhang, Yanmin" , Peter Zijlstra , Sheng Yang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , Jes Sorensen , Gleb Natapov , ziteng.huang@intel.com, Fr?d?ric Weisbecker , Gregory Haskins Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single project Message-ID: <20100324182705.GF3625@ghostprotocols.net> References: <20100324134642.GD14800@8bytes.org> <4BAA1A53.20207@redhat.com> <20100324150137.GE14800@8bytes.org> <4BAA2BF7.4060407@redhat.com> <20100324154605.GG14800@8bytes.org> <4BAA3496.2010901@redhat.com> <20100324155927.GI14800@8bytes.org> <4BAA393A.9000105@redhat.com> <20100324174703.GD3625@ghostprotocols.net> <4BAA57DA.5030707@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BAA57DA.5030707@redhat.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Wed, Mar 24, 2010 at 08:20:10PM +0200, Avi Kivity escreveu: > On 03/24/2010 07:47 PM, Arnaldo Carvalho de Melo wrote: >> Em Wed, Mar 24, 2010 at 06:09:30PM +0200, Avi Kivity escreveu: >> >>> Doesn't perf already has a dependency on naming conventions for finding >>> debug information? >>> >> It looks at several places, from most symbol rich (/usr/lib/debug/, aka >> -debuginfo packages, where we have full symtabs) to poorest (the >> packaged binary, where we may just have a .dynsym). >> >> In an ideal world, it would just get the build-id (a SHA1 cookie that is >> in an ELF session inserted in every binary (aka DSOs), kernel module, >> kallsyms or vmlinux file) and use that to look first in a local cache >> (implemented in perf for a long time already) or in some symbol server. >> >> For instance, for a random perf.data file I collected here in my machine >> I have: >> >> [acme@doppio linux-2.6-tip]$ perf buildid-list | grep libpthread >> 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so >> [acme@doppio linux-2.6-tip]$ >> >> So I don't have to access /lib64/libpthread-2.10.2.so directly, nor some >> convention to get a debuginfo in a local file like: >> >> /usr/lib/debug/lib64/libpthread-2.10.2.so.debug >> >> Instead the tools look at: >> >> [acme@doppio linux-2.6-tip]$ l ~/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 >> lrwxrwxrwx 1 acme acme 73 2010-01-06 18:53 /home/acme/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 -> ../../lib64/libpthread-2.10.2.so/5c68f7afeb33309c78037e374b0deee84dd441f6* >> >> To find the file for that specific build-id, not the one installed in my >> machine (or on the different machine, of a different architecture) that >> may be completely unrelated, a new one, or one for a different arch. > Thanks. I believe qemu could easily act as a symbol server for this use > case. Agreed, but it doesn't even have to :-) We just need to get the build-id in the PERF_RECORD_MMAP event somehow and then get this symbol from elsewhere, say the same DVD/RHN channel/Debian Repository/embedded developer toolkit image not stripped/whatever. Or it may already be in the local cache from last week's perf report session :-) - Arnaldo