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=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,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 8837CC4363D for ; Fri, 2 Oct 2020 07:17:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E7612072E for ; Fri, 2 Oct 2020 07:17:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601623029; bh=VKNPJL2bzFQr7IJTImeYEGk60ykcZAwXa6OGA3vrbfc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=lXRBEu1AUfHrnDhpK2qFe2w0umijKAzlVjUSeRz5E/qzzQiU34OPq2PR1r31pRvVK gTWXqd+DLvNsnbKxkOjCz+Vo0CYLeR23y7CHvSTR2G+LzDNI4ctz5Nlq0Ccf1SowcG 4Aj77JSQ+NGtN46mNDE9tbHGPoxBbhAYi0fNaOHk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726351AbgJBHRI (ORCPT ); Fri, 2 Oct 2020 03:17:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:57854 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbgJBHRI (ORCPT ); Fri, 2 Oct 2020 03:17:08 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DF5FF206B2; Fri, 2 Oct 2020 07:17:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601623027; bh=VKNPJL2bzFQr7IJTImeYEGk60ykcZAwXa6OGA3vrbfc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fHVwk1WBgCO5yj+pxZbKc1aPpUuioNEi4A07Nehen5d0kGzPu6f8GJW2Mdjg7isBt al3Sc1SPhW60rklF4P07uOxwULmV6nYkmI6hHo3koAvM8nhymgE5DkEI6jPQ73hQrv eKyZLqz0uRyKErzBPTcfieFqlmTW0DTMD0ooqwYU= Date: Fri, 2 Oct 2020 16:17:03 +0900 From: Masami Hiramatsu To: Tom Zanussi Cc: rostedt@goodmis.org, axelrasmussen@google.com, mhiramat@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] tracing: Add support for dynamic strings to synthetic events Message-Id: <20201002161703.3961a96e84314fe31157f308@kernel.org> In-Reply-To: <86c164d6476fd1fa9595ec79634b15c25f59e5b0.1601490263.git.zanussi@kernel.org> References: <86c164d6476fd1fa9595ec79634b15c25f59e5b0.1601490263.git.zanussi@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; 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-kernel@vger.kernel.org Hi Tom, On Wed, 30 Sep 2020 13:40:52 -0500 Tom Zanussi wrote: > Currently, sythetic events only support static string fields such as: > > # echo 'test_latency u64 lat; char somename[32]' > /sys/kernel/debug/tracing/synthetic_events > > Which is fine, but wastes a lot of space in the event. > > It also prevents the most commonly-defined strings in the existing > trace events e.g. those defined using __string(), from being passed to > synthetic events via the trace() action. > > With this change, synthetic events with dynamic fields can be defined: > > # echo 'test_latency u64 lat; char somename[]' > /sys/kernel/debug/tracing/synthetic_events Could you add a testcase (and update existing one) of ftracetest for this new feature too? > > And the trace() action can be used to generate events using either > dynamic or static strings: > > # echo 'hist:keys=name:lat=common_timestamp.usecs-$ts0:onmatch(sys.event).test_latency($lat,name)' > /sys/kernel/debug/tracing/events > > The synthetic event dynamic strings are implemented in the same way as > the existing __data_loc strings and appear as such in the format file. > > Signed-off-by: Tom Zanussi > --- > Documentation/trace/events.rst | 15 +- > Documentation/trace/histogram.rst | 18 +++ > kernel/trace/synth_event_gen_test.c | 18 ++- > kernel/trace/trace_events_hist.c | 9 ++ > kernel/trace/trace_events_synth.c | 239 ++++++++++++++++++++++++---- > kernel/trace/trace_synth.h | 4 + And you might also need to update tracefs/README so that user can check whether the kernel supports dynamic string or not. Thank you, -- Masami Hiramatsu