From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755269AbZESNJE (ORCPT ); Tue, 19 May 2009 09:09:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754207AbZESNI4 (ORCPT ); Tue, 19 May 2009 09:08:56 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:45630 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754079AbZESNI4 (ORCPT ); Tue, 19 May 2009 09:08:56 -0400 Date: Tue, 19 May 2009 09:08:41 -0400 From: Christoph Hellwig To: Jeff Moyer Cc: Li Zefan , 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() Message-ID: <20090519130841.GA3801@infradead.org> References: <4A0BB813.9080807@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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.