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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 255FEC04A94 for ; Tue, 1 Aug 2023 14:33:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234610AbjHAOds (ORCPT ); Tue, 1 Aug 2023 10:33:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232198AbjHAOdq (ORCPT ); Tue, 1 Aug 2023 10:33:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D245AE5C; Tue, 1 Aug 2023 07:33:45 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5CE10615C9; Tue, 1 Aug 2023 14:33:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06F9AC433C8; Tue, 1 Aug 2023 14:33:42 +0000 (UTC) Date: Tue, 1 Aug 2023 10:33:40 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Ze Gao , Adrian Hunter , Alexander Shishkin , Arnaldo Carvalho de Melo , Ian Rogers , Ingo Molnar , Jiri Olsa , Mark Rutland , Masami Hiramatsu , Namhyung Kim , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-trace-devel@vger.kernel.org, Ze Gao Subject: Re: [RFC PATCH v3 4/6] sched, tracing: reorganize fields of switch event struct Message-ID: <20230801103340.5dfa7133@gandalf.local.home> In-Reply-To: <20230801114650.GE79828@hirez.programming.kicks-ass.net> References: <20230801090124.8050-1-zegao@tencent.com> <20230801090124.8050-5-zegao@tencent.com> <20230801114650.GE79828@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Tue, 1 Aug 2023 13:46:50 +0200 Peter Zijlstra wrote: > On Tue, Aug 01, 2023 at 05:01:22PM +0800, Ze Gao wrote: > > Report priorities in 'short' and prev_state in 'int' to save > > some buffer space. And also reorder the fields so that we take > > struct alignment into consideration to make the record compact. > > > > Suggested-by: Steven Rostedt (Google) > > I don't see a single line describing the effort you've done to audit > consumers of this tracepoint. > > *IF* you're wanting to break this tracepoint ABI, because seriously > that's what it is, then you get to invest the time and effort to audit > the users. The known major users that I am aware of is raesdaemon, powertop/latencytop, perf, trace-cmd and some bpf tools. The bpf tooling is known to update per kernel. The others all use libtraceevent that can handle this change. What other tools are there? There's Perfetto, but it also looks at tracefs to examine where the values are. There's LTTng, but I believe it uses the raw tracepoint directly and doesn't look at the layout of the ftrace/perf buffers. All other tooling I am slightly aware of uses libtracefs and libtraceveent, as I've been giving many talks on how to use those libraries. -- Steve