From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965166Ab0COPev (ORCPT ); Mon, 15 Mar 2010 11:34:51 -0400 Received: from mail-fx0-f219.google.com ([209.85.220.219]:51368 "EHLO mail-fx0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932208Ab0COPer (ORCPT ); Mon, 15 Mar 2010 11:34:47 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:mime-version :content-type:content-transfer-encoding; b=GdY7S5epcJRzzmfSAcgcEAzL5/DCAIlbTAgQAFMnk3vz2IXEGKKQbGwredj0hvviFn goIJ9Ai/qKW3pahiiIJOxZ3IpEZDe0IaKHG2PFmSejUyev8GGO1vmbIDO0vD5b1oWm5i jzFnSeSxynKHJlgs9USqP8C8Mop2wbXuHViP0= From: =?UTF-8?q?T=C3=B6r=C3=B6k=20Edwin?= To: Ingo Molnar Cc: Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Paul Mackerras , x86@kernel.org, linux-kernel@vger.kernel.org Subject: fix callgraphs of 32-bit processes on 64-bit kernels. Date: Mon, 15 Mar 2010 17:34:19 +0200 Message-Id: <1268667260-5505-1-git-send-email-edwintorok@gmail.com> X-Mailer: git-send-email 1.7.0 MIME-Version: 1.0 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 Hi, Callgraph profiling 32-bit apps on a 64-bit kernel doesn't work. The reason is that perf_callchain_user tries to read a stackframe with 64-bit pointers, which is wrong for a 32-bit process. This patch fixes that, and I am almost able to get nice callgraph profiles from 32-bit apps now! (except for some problems with perf itself when tracing kernel modules, see [1]) Page-faults can be traced nicely (sid-ia32 is a 32-bit chroot): $ sudo perf record -e page-faults -f -g /home/edwin/sid-ia32/usr/bin/glxgears $ sudo perf report ... 45.33% libc-2.10.2.so [.] __GI_memcpy | --- __GI_memcpy _mesa_BufferDataARB _mesa_meta_Clear radeonUserClear r700Clear _mesa_Clear 0x8049367 0x804a6ba __libc_start_main 0x8049111 16.96% libc-2.10.2.so [.] __GI_memset | --- __GI_memset _tnl_init_vertices _swsetup_CreateContext r600CreateContext driCreateNewContext dri2CreateNewContext 0xf77ab7dd 0xf7783c67 0xf778514c 0x804974f 0x804a33d __libc_start_main 0x8049111 And CPU cycles can be traced too in userspace: $ sudo perf record -f -g /home/edwin/sid-ia32/usr/bin/glxgears $ sudo perf report --sort comm,dso [...] 44.97% glxgears r600_dri.so | |--5.85%-- r700SendSPIState | radeonEmitState | r700DrawPrims | | | |--95.45%-- vbo_save_playback_vertex_list | | execute_list | | _mesa_CallList | | neutral_CallList | | | | | |--38.10%-- 0x80494a8 | | | 0x804a6ba | | | __libc_start_main | | | 0x8049111 [....] 40.00% glxgears [kernel] | |--3.14%-- copy_user_generic_string | | | |--71.70%-- 0xffffffffa01b4493 | | 0xffffffffa01b7c0b | | 0xffffffffa018b45b | | 0xffffffffa00ca927 | | 0xffffffffa01c524e | | compat_sys_ioctl | | sysenter_dispatch | | 0xf77ca430 | | drmCommandWriteRead | | 0xf74d7ab5 | | 0xf74d89a4 | | rcommonFlushCmdBufLocked | | rcommonFlushCmdBuf | | radeonFlush | | _mesa_flush | | _mesa_Flush | | 0xf775f270 | | 0x804a6d5 | | __libc_start_main | | 0x8049111 | | | |--15.09%-- 0xffffffffa01c524e | | compat_sys_ioctl | | sysenter_dispatch | | 0xf77ca430 | | drmCommandWriteRead [1] But there is a problem with the perf tool: it can't trace addresses in kernel modules. This is a problem regardless if the traced app is 32-bit or 64-bit; and regardless if I do callgraph profiling or not. See the above trace, where the kernel addresses have all ffffffffa0* without a symbol name. If I look at /proc/kallsyms I can guess the symbols, for example 0xffffffffa01b4493 is probably this one: ffffffffa01b4411 t r600_cs_packet_parse [radeon] If I record/report without callgraph its the same problem: [...] 24.01% glxgears [kernel] [k] 0xffffffffa01b4ee9 3.96% glxgears libdrm_radeon.so.1.0.0 [.] cs_gem_write_reloc 3.53% glxgears r600_dri.so [.] r700SendSPIState 2.77% glxgears r600_dri.so [.] r700DrawPrims 1.99% glxgears r600_dri.so [.] r700SendVSConsts Kernel symbol for 0xffffffffa01b4ee9 is not shown, I can guess it is this one (hey it was an exact match!): ffffffffa01b4ee9 t r600_packet3_check [radeon] It would be good if perf knew how to lookup symbols in kernel modules! Best regards, --Edwin