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=-5.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 2FBFCC433E0 for ; Tue, 16 Jun 2020 10:27:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F36820767 for ; Tue, 16 Jun 2020 10:27:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728160AbgFPK1o (ORCPT ); Tue, 16 Jun 2020 06:27:44 -0400 Received: from mail.ut.ac.ir ([80.66.177.10]:34590 "EHLO mail.ut.ac.ir" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726805AbgFPK0t (ORCPT ); Tue, 16 Jun 2020 06:26:49 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.ut.ac.ir (Postfix) with ESMTP id 2A1271DB301; Tue, 16 Jun 2020 14:56:12 +0430 (+0430) Received: from mail.ut.ac.ir ([127.0.0.1]) by localhost (mail.ut.ac.ir [127.0.0.1]) (amavisd-new, port 10024) with LMTP id gOybnD9-Z9Sf; Tue, 16 Jun 2020 14:56:11 +0430 (+0430) Received: from mail.ut.ac.ir (mail.ut.ac.ir [194.225.0.10]) by mail.ut.ac.ir (Postfix) with ESMTP id C164A1DB317; Tue, 16 Jun 2020 14:56:10 +0430 (+0430) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 16 Jun 2020 14:56:10 +0430 From: ahmadkhorrami To: Steven Rostedt Cc: Linux-trace Users , Arnaldo Carvalho de Melo , linux-perf-users@vger.kernel.org Subject: Re: Perf Script Erroneous User Stack Trace In-Reply-To: <20200615163145.458bd878@oasis.local.home> References: <816cb5f558cd0e528812dff2168ef4ca@ut.ac.ir> <20200615163145.458bd878@oasis.local.home> Message-ID: <02a29da538c753793f663d86e7496207@ut.ac.ir> X-Sender: ahmadkhorrami@ut.ac.ir User-Agent: Roundcube Webmail/1.3.6 Sender: linux-trace-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-users@vger.kernel.org Hi, Thanks, Steven! It was full of patches. Therefore, I thought posting questions might not be OK. I will post my further questions, there. Regards. On 2020-06-16 01:01, Steven Rostedt wrote: > On Sun, 14 Jun 2020 18:13:21 +0430 > ahmadkhorrami wrote: > >> Hi, >> >> I used the following command to sample backtraces for a simple >> "ffmpeg" >> benchmark: >> sudo perf record -d --call-graph dwarf,65528 -c 1000000 -e >> mem_load_uops_retired.l3_miss:u ffmpeg -i >> /media/ahmad/DATA/Videos/video.mp4 -threads 1 -vf spp out.mp4 >> >> As can be seen PEBS is not used, the stack size is set to the maximum >> and the sampling period is quite large. I also limited the thread >> count, >> but this is the first portion of "perf script --no-demangle" output: >> ffmpeg 11750 6670.061261: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeab68844 x264_pixel_avg_w16_avx2+0x4 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> >> ffmpeg 11750 6670.274835: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeab68844 x264_pixel_avg_w16_avx2+0x4 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> >> ffmpeg 11750 6670.496159: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeab8ef89 x264_pixel_sad_x4_16x16_avx2+0x49 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> >> ffmpeg 11750 6670.852598: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeaac97b3 pixel_memset+0x293 (inlined) >> 7fffeaac97b3 plane_expand_border+0x293 (inlined) >> 7fffeaac97b3 x264_frame_expand_border_filtered+0x293 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab463bc x264_fdec_filter_row+0x69c >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab49523 x264_slice_write+0x1873 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab85285 x264_stack_align+0x15 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab45bdb x264_slices_write+0xfb >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 5555561e3d87 [unknown] ([heap]) >> >> ffmpeg 11750 6671.110007: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeab6cdde x264_frame_init_lowres_core_avx2+0x8e >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> >> ffmpeg 11750 6671.463562: 1000000 mem_load_uops_retired.l3_miss:u: >> 0 5080021 N/A|SNP N/A|TLB N/A|LCK N/A >> 7fffeaabf806 x264_macroblock_load_pic_pointers+0x886 (inlined) >> 7fffeaabf806 x264_macroblock_cache_load+0x886 (inlined) >> 7fffeaabf806 x264_macroblock_cache_load_progressive+0x886 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab49204 x264_slice_write+0x1554 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab85285 x264_stack_align+0x15 >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 7fffeab45bdb x264_slices_write+0xfb >> (/usr/lib/x86_64-linux-gnu/libx264.so.152) >> 1c [unknown] ([unknown]) >> >> None of the backtraces are correct. Because none of them begin with >> "__start" or "__GI___clone". I also used "LBR", instead. But it has >> more >> size constraints and, therefore, not suitable. The important thing to >> note is that the problem occurs only with user space events (and for >> all >> events that I checked). I do not think that the problem is with >> DebugInfo. Because I manually used "perf_event_open()" system call >> (without using "Perf") and the problem was still there (with raw >> callstack IPs). >> >> Therefore, I assumed that the problem is inside the kernel. Precisely, >> it should be where the userspace callchain is extracted or dumped. I >> looked for the latter (i.e., the callchain dump implementation) and it >> seemed to be here: >> https://github.com/torvalds/linux/blob/master/kernel/events/core.c#L6786 >> >> But I could not (or, equivalently, did not know how to) view the user >> callchain instruction pointers. >> Am I on the right track? Does anybody know the kernel mechanism for >> extracting userspace callchains? >> >> Please accept my apology for my frequent questions. I tried to get >> around the problem, myself, but it has taken more than three complete >> days and I'm stuck! >> I really appreciate any suggestions. > > No problem, but please note that perf questions are more likely to be > answered via: linux-perf-users@vger.kernel.org and not > linux-trace-users. As linux-trace-users are more for ftrace and not > perf. > > -- Steve