From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753468AbaKQCbN (ORCPT ); Sun, 16 Nov 2014 21:31:13 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:36726 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750978AbaKQCbM (ORCPT ); Sun, 16 Nov 2014 21:31:12 -0500 X-Original-SENDERIP: 10.177.222.235 X-Original-MAILFROM: namhyung@gmail.com From: Namhyung Kim To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , Ingo Molnar , Paul Mackerras , Namhyung Kim , LKML , Jiri Olsa , Adrian Hunter , David Ahern Subject: Re: [PATCH 2/3] perf symbol: Implement a very simple ELF symbol parser References: <1415337606-2186-1-git-send-email-namhyung@kernel.org> <1415337606-2186-2-git-send-email-namhyung@kernel.org> <20141107152618.GM18464@kernel.org> <87ioinv9xb.fsf@sejong.aot.lge.com> <20141110120904.GO18464@kernel.org> Date: Mon, 17 Nov 2014 11:31:10 +0900 In-Reply-To: <20141110120904.GO18464@kernel.org> (Arnaldo Carvalho de Melo's message of "Mon, 10 Nov 2014 09:09:04 -0300") Message-ID: <87sihitv69.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Nov 2014 09:09:04 -0300, Arnaldo Carvalho de Melo wrote: > Em Mon, Nov 10, 2014 at 03:36:48PM +0900, Namhyung Kim escreveu: >> Hi Arnaldo, >> >> On Fri, 7 Nov 2014 12:26:18 -0300, Arnaldo Carvalho de Melo wrote: >> > Em Fri, Nov 07, 2014 at 02:20:05PM +0900, Namhyung Kim escreveu: >> >> It'll be used to show (userspace) symbol names when libelf isn't (or >> >> cannot be) linked. >> > >> > Does this deals with prelink, etc? >> >> I believe so. :) >> >> > >> >> # Overhead Command Shared Object Symbol >> >> # ........ .......... ................. ......................... >> >> # >> >> 37.01% mem-memcpy libc-2.17.so [.] __memcpy_ssse3_back >> >> namhyung@sejong:linux$ readelf -WS /lib64/libc-2.17.so | grep prelink >> [41] .gnu.prelink_undo PROGBITS 0000000000000000 200368 000c30 01 0 0 8 >> >> namhyung@sejong:linux$ nm /lib64/libc-2.17.so | grep __memcpy_ssse3_back >> 0000003153f46f40 t __memcpy_ssse3_back > > Right, in this case most of the samples seems to map to what is expected > for that workload, and the binary was prelinked. Good. > > What about binaries that are not prelinked? IIRC there is code in the > full blown ELF symbol-elf.c file to detect that and act accordingly, > from a _very_ quick look I didn't saw it in this minimalistic ELF symtab > reader, hence my question. AFAIK we deal with prelink'ed binary and normal binary as same way - we only cares about the file offsets. $ perf top --stdio PerfTop: 110 irqs/sec kernel:70.0% exact: 0.0% [4000Hz cycles], (all, 12 CPUs) -------------------------------------------------------------------------------------------- 9.42% perf [.] map__process_kallsym_symbol 8.91% [kernel] [k] kallsyms_expand_symbol.constprop.1 6.80% [kernel] [k] memcpy 6.08% [kernel] [k] vsnprintf ... Thanks, Namhyung