From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7FA90C4360F for ; Fri, 5 Apr 2019 14:09:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B15221852 for ; Fri, 5 Apr 2019 14:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731102AbfDEOJh (ORCPT ); Fri, 5 Apr 2019 10:09:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45546 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727212AbfDEOJg (ORCPT ); Fri, 5 Apr 2019 10:09:36 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6695044F99; Fri, 5 Apr 2019 14:09:36 +0000 (UTC) Received: from treble (ovpn-123-87.rdu2.redhat.com [10.10.123.87]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 70146604A1; Fri, 5 Apr 2019 14:09:31 +0000 (UTC) Date: Fri, 5 Apr 2019 09:09:29 -0500 From: Josh Poimboeuf To: Kairui Song Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Dave Young Subject: Re: [RFC PATCH] perf/x86: make perf callchain work without CONFIG_FRAME_POINTER Message-ID: <20190405140929.pycfea7drnpb2sug@treble> References: <20190404172545.20928-1-kasong@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190404172545.20928-1-kasong@redhat.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 05 Apr 2019 14:09:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 05, 2019 at 01:25:45AM +0800, Kairui Song wrote: > Currently perf callchain is not working properly with ORC unwinder, > we'll get useless in kernel callchain like this: > > perf 6429 [000] 22.498450: kmem:mm_page_alloc: page=0x176a17 pfn=1534487 order=0 migratetype=0 gfp_flags=GFP_KERNEL > ffffffffbe23e32e __alloc_pages_nodemask+0x22e (/lib/modules/5.1.0-rc3+/build/vmlinux) > 7efdf7f7d3e8 __poll+0x18 (/usr/lib64/libc-2.28.so) > 5651468729c1 [unknown] (/usr/bin/perf) > 5651467ee82a main+0x69a (/usr/bin/perf) > 7efdf7eaf413 __libc_start_main+0xf3 (/usr/lib64/libc-2.28.so) > 5541f689495641d7 [unknown] ([unknown]) > > Without CONFIG_FRAME_POINTER, bp is not reserved as frame pointer so > can't get callers frame pointer, instead current frame pointer is > returned when trying to fetch caller registers. The unwinder will error > out early, and end the stacktrace early. > > So instead of let the unwinder start with the dumped register, we start > it right where the unwinding started when the stacktrace is triggered by > trace event directly. And skip until the frame pointer is reached. > > This makes the callchain get the full in kernel stacktrace again: > > perf 6503 [000] 1567.570191: kmem:mm_page_alloc: page=0x16c904 pfn=1493252 order=0 migratetype=0 gfp_flags=GFP_KERNEL > ffffffffb523e2ae __alloc_pages_nodemask+0x22e (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb52383bd __get_free_pages+0xd (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb52fd28a __pollwait+0x8a (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb521426f perf_poll+0x2f (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb52fe3e2 do_sys_poll+0x252 (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb52ff027 __x64_sys_poll+0x37 (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb500418b do_syscall_64+0x5b (/lib/modules/5.1.0-rc3+/build/vmlinux) > ffffffffb5a0008c entry_SYSCALL_64_after_hwframe+0x44 (/lib/modules/5.1.0-rc3+/build/vmlinux) > 7f71e92d03e8 __poll+0x18 (/usr/lib64/libc-2.28.so) > 55a22960d9c1 [unknown] (/usr/bin/perf) > 55a22958982a main+0x69a (/usr/bin/perf) > 7f71e9202413 __libc_start_main+0xf3 (/usr/lib64/libc-2.28.so) > 5541f689495641d7 [unknown] ([unknown]) > > ---- > > Just found with ORC unwinder the perf callchain is unusable, and this > seems fixes it well, any suggestion is welcome, thanks! Hi Kairui, Without CONFIG_FRAME_POINTER, the BP register has no meaning, so I don't see how this patch could work. Also, perf stack traces seem to work fine for me with ORC. Can you give some details on how to recreate the issue? -- Josh