From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755897AbZETIhy (ORCPT ); Wed, 20 May 2009 04:37:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754525AbZETIhr (ORCPT ); Wed, 20 May 2009 04:37:47 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:62216 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754246AbZETIhq (ORCPT ); Wed, 20 May 2009 04:37:46 -0400 Message-ID: <4A13C19E.3000303@cn.fujitsu.com> Date: Wed, 20 May 2009 16:38:54 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Christoph Hellwig CC: Jeff Moyer , Ingo Molnar , Jens Axboe , Steven Rostedt , Frederic Weisbecker , Tom Zanussi , "Theodore Ts'o" , Steven Whitehouse , KOSAKI Motohiro , LKML Subject: Re: [RFC][PATCH] convert block trace points to TRACE_EVENT() References: <4A0BB813.9080807@cn.fujitsu.com> <20090519130841.GA3801@infradead.org> In-Reply-To: <20090519130841.GA3801@infradead.org> 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 Christoph Hellwig wrote: > On Tue, May 19, 2009 at 08:59:29AM -0400, Jeff Moyer wrote: >> I'm not sure I'm comfortable with this. Having had to diagnose >> performance problems using blktrace, I find the dev_t information for >> plugs and unplugs especially interesting. Maybe we can still figure >> this out given the context in the trace, though. Can you comment on >> that? > > The problem is that right now we still allow request queues shared by > multiple gendisks, so we can't get at the gendisk. The blktrace ioctl > interface gets around that by doing the setup with an ioctl on the > block device node and storing the dev_t at that point. > > But I don't think we actually have any drivers left sharing a queue > that way, and I'd love to get rid of that for various reasons. > It will be great if this can be done. >> from the single letter output to the verbose strings? Am I just being a >> curmudgeon? >> >> I have one further question, which will expose my ignorance on this >> implementation. Would the proposed patch change the information >> available to the blktrace utility, > > That's the output from /sys/kernel/debug/tracing/trace when the > block events are enabled. The blktrace utility should continue to > work without changes, although it could be ported to use the ftrace > binary ring buffer directly in the future. > Yes, this patch doesn't affect ioctl-based blktrace or ftrace-plugin blktrace at all. To use blktracer: # echo 1 > /sys/block/sda/trace/enable # echo blk > /debug/tracing/current_tracer # cat /debug/tracing/trace_pipe To use block trace events: # echo 'block:*' > /debug/tracing/set_event # cat /trace_pipe You can mixed-use blktracer and trace events, to see how they differ in the output.