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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 4ED19C11F64 for ; Thu, 1 Jul 2021 13:34:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 239E86141D for ; Thu, 1 Jul 2021 13:34:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230372AbhGANgn (ORCPT ); Thu, 1 Jul 2021 09:36:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229753AbhGANgn (ORCPT ); Thu, 1 Jul 2021 09:36:43 -0400 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7868C061762 for ; Thu, 1 Jul 2021 06:34:11 -0700 (PDT) Received: by mail-pg1-x531.google.com with SMTP id e20so6156864pgg.0 for ; Thu, 01 Jul 2021 06:34:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=SnACoHGHKKSUmroSwFVGCmNRDhzoxlH9nVuiVepkb1o=; b=zCKVemtDZL3ehp7PWxjcfKDxDN51pmQ2ck1pts0xLqfsFeTIRas88OmbvMIzA4dFvo M8C2rBowwV3bq02pJRqrx6XT6BjR29xCvuV7POzUMI64aKMRWLZ+0Zq3ucUE2jumf6iy S1rBKYMUWmMh68QFry//g+ZREkHkE1VYaIXTNCg2D4LXneXuiYJExU7IVu5QXgDJGeqa xccvbodoy4FwRziHM0OglEbzyC9lFbIW1M8fV1Yjwhn/Mjk3aSY8bxsyTzx33X/h3z57 AM/7uqC+nxvidyVV7fcMPb0xf5Oek8z+h27/YJPhcxOXeaX1PUr5tXsxCm5NUlkwx1b+ 7Lfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=SnACoHGHKKSUmroSwFVGCmNRDhzoxlH9nVuiVepkb1o=; b=Va5FoaJ5aRdRBcz8Xar0g/oCnJ4wekHQclpFgbfmfN7B4Zxx+QT2opWNBbli4dz8Qu r2gMhYE61A7yhXbFMOn6xTPx+Ku/umP/znfsZUwrQ5Prl9c7v9MFPyjw8HGvGSf/Xt56 imFIANzvoIQeqTzLU1of3lmKHEPvIyuRuXLhQ0DIslztfypDkP9i6tIGpabAmH3ndp8E vvk3HTOcq4WVyDP/FbvVhugoJ4pqszFR/Hlpjl9TGxUE5KeLGlGilQ2Hk1K3pgr8LZJs +e6YqRrelYmVqN7BlKQF7XOG+fa259m3Rt3GYwkA6Ry3AqzHGPk6aGLZpDPcbJYaJSio y1Ew== X-Gm-Message-State: AOAM532P72cK5U8xwHrZ779sEdJz3j0Jb3wYnooAz/gaaPGAHlyO5qex zkPjaTMdqFwtCw5lvKWOwPB3Bg== X-Google-Smtp-Source: ABdhPJykFDVO5eAJi3DVkcgV0nKVtx9Poi5lkDhj2P0Tz4JkhKgYevSdgvCDB7Pae/1N5b7+cy/IBw== X-Received: by 2002:a62:4e96:0:b029:305:a36c:fc6 with SMTP id c144-20020a624e960000b0290305a36c0fc6mr35402pfb.70.1625146451190; Thu, 01 Jul 2021 06:34:11 -0700 (PDT) Received: from leoy-ThinkPad-X240s ([103.207.71.35]) by smtp.gmail.com with ESMTPSA id gl17sm10080799pjb.13.2021.07.01.06.34.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Jul 2021 06:34:10 -0700 (PDT) Date: Thu, 1 Jul 2021 21:34:04 +0800 From: Leo Yan To: James Clark Cc: acme@kernel.org, mathieu.poirier@linaro.org, coresight@lists.linaro.org, al.grant@arm.com, branislav.rankov@arm.com, denik@chromium.org, suzuki.poulose@arm.com, anshuman.khandual@arm.com, Mike Leach , John Garry , Will Deacon , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf cs-etm: Delay decode of non-timeless data until cs_etm__flush_events() Message-ID: <20210701133404.GB91264@leoy-ThinkPad-X240s> References: <20210609130421.13934-1-james.clark@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210609130421.13934-1-james.clark@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On Wed, Jun 09, 2021 at 04:04:20PM +0300, James Clark wrote: > Currently, timeless mode starts the decode on PERF_RECORD_EXIT, and > non-timeless mode starts decoding on the fist PERF_RECORD_AUX record. > > This can cause the "data has no samples!" error if the first > PERF_RECORD_AUX record comes before the first (or any relevant) > PERF_RECORD_MMAP2 record because the mmaps are required by the decoder > to access the binary data. > > This change pushes the start of non-timeless decoding to the very end of > parsing the file. The PERF_RECORD_EXIT event can't be used because it > might not exist in system-wide or snapshot modes. > > I have not been able to find the exact cause for the events to be > intermittently in the wrong order in the basic scenario: > > perf record -e cs_etm/@tmc_etr0/u top > > But it can be made to happen every time with the --delay option. This is > because "enable_on_exec" is disabled, which causes tracing to start > before the process to be launched is exec'd. For example: > > perf record -e cs_etm/@tmc_etr0/u --delay=1 top > perf report -D | grep 'AUX\|MAP' > > 0 16714475632740 0x520 [0x40]: PERF_RECORD_AUX offset: 0 size: 0x30 flags: 0 [] > 0 16714476494960 0x5d0 [0x40]: PERF_RECORD_AUX offset: 0x30 size: 0x30 flags: 0 [] > 0 16714478208900 0x660 [0x40]: PERF_RECORD_AUX offset: 0x60 size: 0x30 flags: 0 [] > 4294967295 16714478293340 0x700 [0x70]: PERF_RECORD_MMAP2 8712/8712: [0x557a460000(0x54000) @ 0 00:17 5329258 0]: r-xp /usr/bin/top > 4294967295 16714478353020 0x770 [0x88]: PERF_RECORD_MMAP2 8712/8712: [0x7f86f72000(0x34000) @ 0 00:17 5214354 0]: r-xp /usr/lib/aarch64-linux-gnu/ld-2.31.so > > Another scenario in which decoding from the first aux record fails is a > workload that forks. Although the aux record comes after 'bash', it > comes before 'top', which is what we are interested in. For example: > > perf record -e cs_etm/@tmc_etr0/u -- bash -c top > perf report -D | grep 'AUX\|MAP' > > 4294967295 16853946421300 0x510 [0x70]: PERF_RECORD_MMAP2 8723/8723: [0x558f280000(0x142000) @ 0 00:17 5213953 0]: r-xp /usr/bin/bash > 4294967295 16853946543560 0x580 [0x88]: PERF_RECORD_MMAP2 8723/8723: [0x7fbba6e000(0x34000) @ 0 00:17 5214354 0]: r-xp /usr/lib/aarch64-linux-gnu/ld-2.31.so > 4294967295 16853946628420 0x608 [0x68]: PERF_RECORD_MMAP2 8723/8723: [0x7fbba9e000(0x1000) @ 0 00:00 0 0]: r-xp [vdso] > 0 16853947067300 0x690 [0x40]: PERF_RECORD_AUX offset: 0 size: 0x3a60 flags: 0 [] > ... > 0 16853966602580 0x1758 [0x40]: PERF_RECORD_AUX offset: 0xc2470 size: 0x30 flags: 0 [] > 4294967295 16853967119860 0x1818 [0x70]: PERF_RECORD_MMAP2 8723/8723: [0x5559e70000(0x54000) @ 0 00:17 5329258 0]: r-xp /usr/bin/top > 4294967295 16853967181620 0x1888 [0x88]: PERF_RECORD_MMAP2 8723/8723: [0x7f9ed06000(0x34000) @ 0 00:17 5214354 0]: r-xp /usr/lib/aarch64-linux-gnu/ld-2.31.so > 4294967295 16853967237180 0x1910 [0x68]: PERF_RECORD_MMAP2 8723/8723: [0x7f9ed36000(0x1000) @ 0 00:00 0 0]: r-xp [vdso] > > A third scenario is when the majority of time is spent in a shared > library that is not loaded at startup. For example a dynamically loaded > plugin. > > Testing > ======= > > Testing was done by checking if any samples that are present in the > old output are missing from the new output. Timestamps must be > stripped out with awk because now they are set to the last AUX sample, > rather than the first: > > ./perf script $4 | awk '!($4="")' > new.script > ./perf-default script $4 | awk '!($4="")' > default.script > comm -13 <(sort -u new.script) <(sort -u default.script) > > Testing showed that the new output is a superset of the old. When lines > appear in the comm output, it is not because they are missing but > because [unknown] is now resolved to sensible locations. For example > last putp branch here now resolves to libtinfo, so it's not missing > from the output, but is actually improved: > > Old: > top 305 [001] 1 branches:uH: 402830 _init+0x30 (/usr/bin/top.procps) => 404a1c [unknown] (/usr/bin/top.procps) > top 305 [001] 1 branches:uH: 404a20 [unknown] (/usr/bin/top.procps) => 402970 putp@plt+0x0 (/usr/bin/top.procps) > top 305 [001] 1 branches:uH: 40297c putp@plt+0xc (/usr/bin/top.procps) => 0 [unknown] ([unknown]) > New: > top 305 [001] 1 branches:uH: 402830 _init+0x30 (/usr/bin/top.procps) => 404a1c [unknown] (/usr/bin/top.procps) > top 305 [001] 1 branches:uH: 404a20 [unknown] (/usr/bin/top.procps) => 402970 putp@plt+0x0 (/usr/bin/top.procps) > top 305 [001] 1 branches:uH: 40297c putp@plt+0xc (/usr/bin/top.procps) => 7f8ab39208 putp+0x0 (/lib/libtinfo.so.5.9) > > In the following two modes, decoding now works and the "data has no > samples!" error is not displayed any more: > > perf record -e cs_etm/@tmc_etr0/u -- bash -c top > perf record -e cs_etm/@tmc_etr0/u --delay=1 top > > In snapshot mode, there is also an improvement to decoding. Previously > samples for the 'kill' process that was used to send SIGUSR2 were > completely missing, because the process hadn't started yet. But now > there are additional samples present: > > perf record -e cs_etm/@tmc_etr0/u --snapshot -a > perf script > > stress 19380 [003] 161627.938153: 1000000 instructions:uH: aaaabb612fb4 [unknown] (/usr/bin/stress) > kill 19644 [000] 161627.938153: 1000000 instructions:uH: ffffae0ef210 [unknown] (/lib/aarch64-linux-gnu/ld-2.27.so) > stress 19380 [003] 161627.938153: 1000000 instructions:uH: ffff9e754d40 random_r+0x20 (/lib/aarch64-linux-gnu/libc-2.27.so) > > Also tested was the round trip of 'perf inject' followed by 'perf > report' which has the same differences and improvements. > > Signed-off-by: James Clark Excellent work, James! I learned several things from it :) I went through the testing cases one by one, have verified all elaborated cases (but I don't verify injection cases): Reviewed-by: Leo Yan Tested-by: Leo Yan