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=-7.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7F083C432C0 for ; Tue, 3 Dec 2019 10:22:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B0A620684 for ; Tue, 3 Dec 2019 10:22:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YCZj9NxZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726075AbfLCKWp (ORCPT ); Tue, 3 Dec 2019 05:22:45 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:47923 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725907AbfLCKWp (ORCPT ); Tue, 3 Dec 2019 05:22:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575368563; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vJnlkqQuX45vF9FHqxHeZsY8ZPt9Nh2gdIeo4L+JajI=; b=YCZj9NxZkFV66Dzclkbq23qIf2brrRn6k6rvfiJKMp6OQGfh0WEdS3hcxs6hyad2E28nkf bz68QGxQvZ2NimAm2WFUBWUGaSfLde4NSUKnxPhZjC9QKZ3wnUel1YPTB2rU6DVd5Wlum4 7IeZvky3YEDWoVitHjByBEvobzyvGEk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-415-HN7Q1R1HNFiQSSXPogrzGA-1; Tue, 03 Dec 2019 05:22:38 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EA1991005502; Tue, 3 Dec 2019 10:22:36 +0000 (UTC) Received: from krava (unknown [10.43.17.48]) by smtp.corp.redhat.com (Postfix) with SMTP id 223FD5C557; Tue, 3 Dec 2019 10:22:34 +0000 (UTC) Date: Tue, 3 Dec 2019 11:22:34 +0100 From: Jiri Olsa To: Ivan Babrou Cc: Arnaldo Carvalho de Melo , linux-kernel , linux-perf-users@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Alexander Shishkin , Namhyung Kim , kernel-team Subject: Re: perf is unable to read dward from go programs Message-ID: <20191203102234.GE17468@krava> References: <20191129134929.GA26903@krava> <20191129151436.GB26963@kernel.org> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: HN7Q1R1HNFiQSSXPogrzGA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 02, 2019 at 11:49:55AM -0800, Ivan Babrou wrote: > I've tried building with libdw with mixed results: >=20 > 1. I can see stacks from some Go programs that were invisible before (yay= !) >=20 > 2. Warnings like below still appear in great numbers for a system-wide > flamegraph: >=20 > BFD: Dwarf Error: found dwarf version '18345', this reader only > handles version 2, 3 and 4 information. >=20 > I'm not sure how to pinpoint this to a particular binary and would > appreciate some help with this. I'd need some way of reproducing this, could you please paste me command lines you used? >=20 > 3. It takes minutes to produce a flamegraph of a running system > whereas before it only took seconds. See this flamegraph of "perf > script" itself: >=20 > * https://gist.github.com/bobrik/a9c46cffe9daa5840abd137443d8bab0#file-fl= amegraph-perf-svg >=20 > Seems like there is no caching and debug info is getting reparsed > continuously for every stack. It's possible that it was not an issue > before, because we spent no time decompressing dwarf. possibly, if we have some clear reproducer we can hand it to the libdw guy that helped us develop this >=20 > 4. Pretty much all luajit frames stacks that were marked as unknown > before are now gone. >=20 > See before and after here: https://imgur.com/a/1LNfqAk >=20 > Before: >=20 > nginx-cache 94572 446642.722028: 10101010 cpu-clock: > 5607d8d56718 ngx_http_lua_shdict_lookup+0x48 (inlined) > 5607d8d5a09d ngx_http_lua_ffi_shdict_incr+0xcd > (/usr/local/nginx-cache/sbin/nginx-cache) > 560802fe58e4 [unknown] (/tmp/perf-94572.map) >=20 > After: >=20 > nginx-cache 94572 446543.008703: 10101010 cpu-clock: > 5607d8d56718 ngx_http_lua_shdict_lookup+0x48 (inlined) > 5607d8d59da7 ngx_http_lua_ffi_shdict_get+0x197 > (/usr/local/nginx-cache/sbin/nginx-cache) >=20 > The key is /tmp/perf-*.map frame at the bottom. I don't know if it's > expected, but we grew dependent on knowing this. >=20 > 5. Special [[stack]], [[heap]] and [anon] frames are also gone, and > you can see the following during "perf script" run: >=20 > open("[stack]", O_RDONLY) =3D -1 ENOENT (No such file or di= rectory) > open("[heap]", O_RDONLY) =3D -1 ENOENT (No such file or di= rectory) > open("//anon", O_RDONLY) =3D -1 ENOENT (No such file or di= rectory) strange, let's start with the reproducer and I'll check on this if I see it thanks, jirka