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 2D9D2C83F2C for ; Tue, 5 Sep 2023 16:45:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229882AbjIEQp3 (ORCPT ); Tue, 5 Sep 2023 12:45:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353610AbjIEQ2s (ORCPT ); Tue, 5 Sep 2023 12:28:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA2F42D54; Tue, 5 Sep 2023 09:18:51 -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 08A3160A71; Tue, 5 Sep 2023 16:17:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9B81C433C7; Tue, 5 Sep 2023 16:17:25 +0000 (UTC) Date: Tue, 5 Sep 2023 12:17:44 -0400 From: Steven Rostedt To: Zheng Yejian Cc: , , , Subject: Re: [PATCH] tracing: Fix unexpected ring buffer expand by instance Message-ID: <20230905121744.538b92cc@gandalf.local.home> In-Reply-To: <20230905121714.3229131-1-zhengyejian1@huawei.com> References: <20230905121714.3229131-1-zhengyejian1@huawei.com> 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-kernel@vger.kernel.org On Tue, 5 Sep 2023 20:17:14 +0800 Zheng Yejian wrote: > The ring buffer of global_trace is set to the minimum size in > order to save memory on boot up and then it will be expand when > some trace feature enabled. > > However currently operations under an instance can also cause > global_trace ring buffer being expanded, and the expanded memory > would be wasted if global_trace then not being used. > > See following case, we enable 'sched_switch' event in instance 'A', then > ring buffer of global_trace is unexpectedly expanded to be 1410KB, also > the '(expanded: 1408)' from 'buffer_size_kb' of instance is confusing. > > # cd /sys/kernel/tracing > # mkdir instances/A > # cat buffer_size_kb > 7 (expanded: 1408) > # cat instances/A/buffer_size_kb > 1410 (expanded: 1408) > # echo sched:sched_switch > instances/A/set_event > # cat buffer_size_kb > 1410 > # cat instances/A/buffer_size_kb > 1410 > > To fix it, we can: > - Make 'ring_buffer_expanded' as a member of 'struct trace_array'; > - Make 'ring_buffer_expanded' of instance is defaultly true, > global_trace is defaultly false; > - In order not to expose 'global_trace' outside of file > 'kernel/trace/trace.c', introduce trace_set_ring_buffer_expanded() > to set 'ring_buffer_expanded' as 'true'; > - Pass the expected trace_array to tracing_update_buffers(). > > Signed-off-by: Zheng Yejian > --- > kernel/trace/trace.c | 46 ++++++++++++++++++++----------------- > kernel/trace/trace.h | 9 ++++++-- > kernel/trace/trace_events.c | 22 ++++++++++-------- > 3 files changed, 44 insertions(+), 33 deletions(-) > Looks good, but as the merge window is still open, it will need to wait till it is closed to be reviewed. Thanks, -- Steve