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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 A9660C388F7 for ; Tue, 10 Nov 2020 12:22:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58FE3206B6 for ; Tue, 10 Nov 2020 12:22:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="2A+m1iHA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730441AbgKJMWn (ORCPT ); Tue, 10 Nov 2020 07:22:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40646 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726861AbgKJMWm (ORCPT ); Tue, 10 Nov 2020 07:22:42 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1943C0613CF for ; Tue, 10 Nov 2020 04:22:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3/1Uid5NXV02fVcliXKfyabT8T10rQnq7Svabpzfx6E=; b=2A+m1iHAGoU/HdwXwcZvWhxWWB zBiXeNqBCfidAPG4wb63pWEAew0Euxzpf95/s5gQsQTIXoO/xsTN6a7Nhxq4Ez0speEvRt+Oa6LI3 haNxoh8Vpu9nos/F6X88HLocpfqNRE6cu+f963lqiC6+F4uPu4EARml6MtTkTrAFcBNsMBdKrvGX+ XeJ2vybnjj5kax2+tdrpZFKcDlTVDGOS08ogV6OUal2kUfre5zvmdDCV0vE6pd7qaesEqrrV3VLwS hVRUbI2w41KR1tixNhice0ZmQHw0U0tOdZXEnIvfTsH/xiDomNs3yJVlWsZghoMsJEPf+H9dg76m0 Sz+g9Wig==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kcSfR-0004R9-Ov; Tue, 10 Nov 2020 12:22:34 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 85EFB30705A; Tue, 10 Nov 2020 13:22:32 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7744C2C29A9E4; Tue, 10 Nov 2020 13:22:32 +0100 (CET) Date: Tue, 10 Nov 2020 13:22:32 +0100 From: Peter Zijlstra To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , lkml , Ingo Molnar , Mark Rutland , Namhyung Kim , Alexander Shishkin , Michael Petlan , Song Liu , Ian Rogers , Stephane Eranian , Alexey Budankov , Andi Kleen , Adrian Hunter Subject: Re: [PATCH 03/24] perf: Add build id data in mmap2 event Message-ID: <20201110122232.GH2594@hirez.programming.kicks-ass.net> References: <20201109215415.400153-1-jolsa@kernel.org> <20201109215415.400153-4-jolsa@kernel.org> <20201110080716.GU2594@hirez.programming.kicks-ass.net> <20201110115426.GA348806@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201110115426.GA348806@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 10, 2020 at 08:54:26AM -0300, Arnaldo Carvalho de Melo wrote: > Em Tue, Nov 10, 2020 at 09:07:16AM +0100, Peter Zijlstra escreveu: > > On Mon, Nov 09, 2020 at 10:53:54PM +0100, Jiri Olsa wrote: > > > Adding support to carry build id data in mmap2 event. > > > > > > The build id data replaces maj/min/ino/ino_generation > > > fields, whichc are also used to identify map's binary, > > > so it's ok to replace them with build id data: > > > > > > union { > > > struct { > > > u32 maj; > > > u32 min; > > > u64 ino; > > > u64 ino_generation; > > > }; > > > struct { > > > u8 build_id[20]; > > > u8 build_id_size; > > > > What's the purpose of a size field for a fixed size array? Also, I'd > > flip the order of these fields, first have the size and then the array. > > There can be different types of build-ids, with different sizes, > flipping the order of the fields is indeed sensible, as we could then > support even larger build_ids if the need arises :) 3 whole bytes.. whooo!