From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757667AbZCYHZ3 (ORCPT ); Wed, 25 Mar 2009 03:25:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752531AbZCYHZV (ORCPT ); Wed, 25 Mar 2009 03:25:21 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:56401 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751474AbZCYHZU (ORCPT ); Wed, 25 Mar 2009 03:25:20 -0400 Message-ID: <49C9DC75.9080301@cn.fujitsu.com> Date: Wed, 25 Mar 2009 15:25:41 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Jens Axboe CC: Ingo Molnar , Arnaldo Carvalho de Melo , Frederic Weisbecker , Steven Rostedt , LKML Subject: Re: [RFC][PATCH] blktrace: fix original blktrace References: <49C99BD2.9090503@cn.fujitsu.com> <20090325070726.GD27476@kernel.dk> In-Reply-To: <20090325070726.GD27476@kernel.dk> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe wrote: > On Wed, Mar 25 2009, Li Zefan wrote: >> I'm wondering what we are going to do with the original blktrace which >> is using relay and is used via ioctl. >> >> The problem is currently it's totally broken. You can use ftrace to see >> the output of blktrace, but user-space blktrace is unusable. >> >> With this patch, both ioctl and ftrace can be used, but of course you >> can't use both of them at the same time. > > Even if ftrace was as fast as storing huge amounts of data as blktrace, > it's still of utmost importance that nothing is broken there. There are agreed > people actually USING this tracing to do real work, it's not a > playground. > and we are using blktrace to test the cgroup-based io controller > I appreciate the efforts to unify and improve our tracing, but we must > not be breaking blktrace along the way. Otherwise the whole thing goes this patch fixes it. it's broken by "blktrace: add ftrace plugin" (c71a896154119f4ca9e89d6078f5f63ad60ef199) @@ -131,13 +162,14 @@ static void __blk_add_trace() - if (unlikely(bt->trace_state != Blktrace_running)) + if (unlikely(bt->trace_state != Blktrace_running || !blk_tracer_enabled)) return; > back to block/blktrace.c, period. >