Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754027Ab2KGO4U (ORCPT ); Wed, 7 Nov 2012 09:56:20 -0500 Received: from mail-lb0-f174.google.com ([209.85.217.174]:53069 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752630Ab2KGO4E convert rfc822-to-8bit (ORCPT ); Wed, 7 Nov 2012 09:56:04 -0500 MIME-Version: 1.0 In-Reply-To: <509A75F3.3060409@hitachi.com> References: <20121106205220.GF13629@infradead.org> <509A75F3.3060409@hitachi.com> Date: Wed, 7 Nov 2012 15:56:02 +0100 Message-ID: Subject: Re: Re: [PATCH v2 00/16] perf: add memory access sampling support From: Stephane Eranian To: Masami Hiramatsu Cc: Arnaldo Carvalho de Melo , LKML , Andi Kleen , Peter Zijlstra , Namhyung Kim , Jiri Olsa , Ingo Molnar , "yrl.pp-manager.tt@hitachi.com" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3754 Lines: 91 On Wed, Nov 7, 2012 at 3:53 PM, Masami Hiramatsu wrote: > (2012/11/07 5:52), Arnaldo Carvalho de Melo wrote: >> Em Mon, Nov 05, 2012 at 02:50:47PM +0100, Stephane Eranian escreveu: >>> Or if one is interested in the data view: >>> $ perf mem -t load rep --sort=symbol_daddr,cost >>> # Samples: 19K of event 'cpu/mem-loads/pp' >>> # Total cost : 1013994 >>> # Sort order : symbol_daddr,cost >>> # >>> # Overhead Samples Data Symbol Cost >>> # ........ ........... ...................... ....... >>> # >>> 0.10% 1 [.] 0x00007f67dffe8038 986 >>> 0.09% 1 [.] 0x00007f67df91a750 890 >>> 0.08% 1 [.] 0x00007f67e288fba8 826 >>> >> >>> CAVEAT: Note that the data addresses are not resolved correctly currently due to a >>> problem in perf data symbol resolution code which I have not been able to >>> uncover so far. >> >> Stephane, >> >> Those data addresses mostly are on the stack, we need reverse >> resolution using DWARF location expressions to figure out what is the >> name of a variable that is on a particular address, etc. >> >> Masami, have you played with this already? I mean: > > No, but it looks interesting. I'll try :) > >> >> [root@sandy acme]# perf mem -t load rep --stdio --sort=symbol,symbol_daddr,cost >> # Samples: 30 of event 'cpu/mem-loads/pp' >> # Total cost : 640 >> # Sort order : symbol,symbol_daddr,cost >> # >> # Overhead Samples Symbol Data Symbol Cost >> # ........ ........... ...................... ...................... ....... >> # >> 55.00% 1 [k] lookup_fast [k] 0xffff8803b7521bd4 352 >> 5.47% 1 [k] cache_alloc_refill [k] 0xffff880407705024 35 >> 3.44% 1 [k] cache_alloc_refill [k] 0xffff88041d8527d8 22 >> 3.28% 1 [k] run_timer_softirq [k] 0xffff88041e2c3e90 21 >> 2.50% 1 [k] __list_add [k] 0xffff8803b7521d68 16 >> 2.19% 1 [.] __strcoll_l [.] 0x00007fffa8d44080 14 >> 1.88% 1 [.] __strcoll_l [.] 0x00007fffa8d44104 12 >> >> If we go to the annotation browser to see where is that lookup_fast hitting we get: >> >> 100.00 │ mov -0x34(%rbp),%eax >> >> How to map 0xffff8803b7521bd4 to a stack variable, struct members and all? > > If perf stores %rbp value, we can do forward searching from local variables > in this scope block. In some cases, the memory is dereferenced by another > pointer. In that case, it is hard to do that (perhaps, we need to disassemble > it and reverse execution). But in most case of the memory address on a stack, > it will work, I think. > PEBS-LL does store rbp but it is not yet exposed. That will be in a follow-up patch. > Thank you, > >> >> Humm, for userspace we have PERF_SAMPLE_REGS_USER for the dwarf unwinder we >> need for userspace, but what about reverse mapping of kernel variables? Jiri? >> >> - Arnaldo >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > > > -- > Masami HIRAMATSU > IT Management Research Dept. Linux Technology Center > Hitachi, Ltd., Yokohama Research Laboratory > E-mail: masami.hiramatsu.pt@hitachi.com > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/