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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 1E57DC2BA83 for ; Wed, 12 Feb 2020 13:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D940C2082F for ; Wed, 12 Feb 2020 13:31:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cTKJfozo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727692AbgBLNbd (ORCPT ); Wed, 12 Feb 2020 08:31:33 -0500 Received: from mail-qv1-f66.google.com ([209.85.219.66]:42875 "EHLO mail-qv1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725887AbgBLNbd (ORCPT ); Wed, 12 Feb 2020 08:31:33 -0500 Received: by mail-qv1-f66.google.com with SMTP id dc14so890112qvb.9; Wed, 12 Feb 2020 05:31:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=myZUd9/EmvSZIipj4aycXbLr16w30buYk0xA+FZcMZU=; b=cTKJfozoaBYtXHn0s+YZrxbQ5Q62gzDLv9rd50YJ0haP8AcvNBIUZ69Ck4GUzesGfz sqEVGTkAMMoKN+sVP+yOiF3WjE+ttFF5VWIimqt0qNo+sJF7glJZcQlAuhtDUUywFhMf 1D5Md8cAOE2iCOnq75X47ajgDrxxbt9DLSXwrVzW8wCJtZwuHH8wBNta6imu1UnWupRw UPSwtvYyDdFJdzGi+ljhloCjVmI3PvKKRsTYR/Hj52/hQQZmj9b2tZ7F7JaPJR/9TxYy 1xaHywEvVCWUeqMW1/aj0udI92kfP8NTdabgLyTc+LyHQrIPbIZQdaD1s9lp1y6WeAjO qCTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=myZUd9/EmvSZIipj4aycXbLr16w30buYk0xA+FZcMZU=; b=G7W2TJNbhQ5+m5pSnZ8AQ6nnBUVrQ2BsRTvr8UGkvoPQzcRfPRPt2XrJDJGb3Oj+nM AIUpRHS4cK1/jMGnasmFEY/vS/Z0g/lpe+ey+IqT6C9moMkjpOm8owDHf7vPi7F+vm4I UQoOcUAdmDG4dJI5azm2VxZZKh/wIjvPnkQ1CY/RtPVgvv4OBn0/jw90iOw9GZIy5gLw hGUx/VWg95fTyPFXImN+J7Kwrr6uP/q5bX2l9x1ipfHVX0WsCSbygPJ28W59SSmGrNvo vBKb62clv9Q47EtAIWwYM/jbSfNKhGz4Nvnnaf5/zYqbS7yggaKIgyprnrJQsZRAW1qR +46A== X-Gm-Message-State: APjAAAVxPRZCcXXBUdOm/3C7WEm1HkRrNiJPtW8XR6tCeP8rCRJ6tgs6 jNI8WcMF5L/lz7wcxkixPc4= X-Google-Smtp-Source: APXvYqzpkZnamk4UBoQA1UDxWfKB08dA8uiLqvcrWLWGIIuI2v01Q/QkJB6psL0bbS6jrec2cfK/mg== X-Received: by 2002:a0c:edc3:: with SMTP id i3mr7257890qvr.29.1581514292041; Wed, 12 Feb 2020 05:31:32 -0800 (PST) Received: from quaco.ghostprotocols.net ([179.97.37.151]) by smtp.gmail.com with ESMTPSA id t16sm170213qkg.96.2020.02.12.05.31.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2020 05:31:27 -0800 (PST) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 9E60740A7D; Wed, 12 Feb 2020 10:31:25 -0300 (-03) Date: Wed, 12 Feb 2020 10:31:25 -0300 To: Jiri Olsa Cc: =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Netdev , bpf , Andrii Nakryiko , Yonghong Song , Song Liu , Martin KaFai Lau , Jakub Kicinski , David Miller , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , John Fastabend , Jesper Dangaard Brouer Subject: Re: [PATCH 00/14] bpf: Add trampoline and dispatcher to /proc/kallsyms Message-ID: <20200212133125.GA22501@kernel.org> References: <20200208154209.1797988-1-jolsa@kernel.org> <20200210161751.GC28110@krava> <20200211193223.GI3416@kernel.org> <20200212111346.GF183981@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200212111346.GF183981@krava> X-Url: http://acmel.wordpress.com Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Wed, Feb 12, 2020 at 12:13:46PM +0100, Jiri Olsa escreveu: > On Tue, Feb 11, 2020 at 04:32:23PM -0300, Arnaldo Carvalho de Melo wrote: > > Historically vmlinux was preferred because it contains function sizes, > > but with all these out of the blue symbols, we need to prefer starting > > with /proc/kallsyms and, as we do now, continue getting updates via > > PERF_RECORD_KSYMBOL. > > Humm, but then trampolines don't generate that, right? Or does it? If it > > doesn't, then we will know about just the trampolines in place when the > > record/top session starts, reparsing /proc/kallsyms periodically seems > > excessive? > I plan to extend the KSYMBOL interface to contain trampolines/dispatcher > data, That seems like the sensible, without looking too much at all the details, to do, yes. > plus we could do some inteligent fallback to /proc/kallsyms in case > vmlinux won't have anything At this point what would be the good reason to prefer vmlinux instead of going straight to using /proc/kallsyms? We have support for taking a snapshot of it at 'perf top' start, i.e. right at the point we need to resolve a kernel symbol, then we get PERF_RECORD_KSYMBOL for things that gets in place after that. And as well we save it to the build-id cache so that later, at 'perf report/script' time we can resolve kernel symbols, etc. vmlinux is just what is in there right before boot, after that, for quite some time, _lots_ of stuff happens :-) - Arnaldo