Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754721AbZFKROr (ORCPT ); Thu, 11 Jun 2009 13:14:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753011AbZFKROj (ORCPT ); Thu, 11 Jun 2009 13:14:39 -0400 Received: from mail-ew0-f210.google.com ([209.85.219.210]:56023 "EHLO mail-ew0-f210.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752143AbZFKROi (ORCPT ); Thu, 11 Jun 2009 13:14:38 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=iaakkaUwPQHeNaRHYlKXL+Ki2rmz4Z+FGDq057Uzf/lj8ajrhWhd/qEMmLqNifmgUa d4K4wFJsNrpul01wYDbevVZ8ymPDfaE2pkn2qmQ7OPeEhlfQKvIeFK4VSbXcD77sBu4B BwZG6kJz78+rDWYNu1r38sv8B2MPJMnTN5x9g= Date: Thu, 11 Jun 2009 19:14:36 +0200 From: Frederic Weisbecker To: Theodore Tso , Christoph Hellwig , Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org, Andrew Morton , Minchan Kim , Mel Gorman , Rik van Riel , Pekka Enberg , Peter Zijlstra , Mathieu Desnoyers , Lai Jiangshan , Zhaolei , KOSAKI Motohiro , Jason Baron , Jiaying Zhang , Tom Zanussi , Xiao Guangrong Subject: Re: [PATCH 00/11] [GIT PULL] more updates for the tag format Message-ID: <20090611171434.GA6011@nowhere> References: <20090610054206.510574695@goodmis.org> <20090610092644.GA20889@elte.hu> <20090610130127.GA6647@mit.edu> <20090610160303.GA10240@mit.edu> <20090611130318.GB14220@infradead.org> <20090611154751.GD9275@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090611154751.GD9275@mit.edu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2637 Lines: 53 On Thu, Jun 11, 2009 at 11:47:51AM -0400, Theodore Tso wrote: > On Thu, Jun 11, 2009 at 09:03:18AM -0400, Christoph Hellwig wrote: > > On Wed, Jun 10, 2009 at 12:03:03PM -0400, Theodore Tso wrote: > > > Yes, another approach for handling this case would be to take my > > > "jbd2_dev_to_name" function and support it as a first-class tagged > > > type; after all, I'm sure ext4 won't be the only place that would like > > > to take a dev_t and print the device name. So this could certainly be > > > fixed by adding some kind of "" sort of tagged name. > > > > We should absolutely agree on one way to represent block device for > > tracers. At this point xfs, gfs2 and the block tracer all use > > major/minor. I agree that having a name would be nicer for text output, > > but I really want to keep the dev_t for the binary output. We should > > also make sure we agree on a field name so that filtering will work > > the same for all block-related tracers (especially important if we want > > to trace something from the filesystem down to the block layer). > > And I want to keep the dev_t as what stored in the ring buffer for > space reasons; but the text name is far more convient in terms of > being human-readable, *especially* given there are some crazy people > out there wanting to make major/minor numbers be completely random. > The problem with that is that a log trace file might not be useful > after a reboot, unless someone had enough foresight to save the device > mappings which were in effect at the that the trace was taken. > > So if we store the dev_t in the ring buffer, and have a way of > translating the dev_t into a human-friendly name at printk happen, I > think that meets both of our goals. That would imply that filtering > would be using a device number, which would certainly be more > efficient than doing a string compare. > > - Ted For the filters, we could enter the text name which would be internally converted into a dev_t, there should be no problem. Also the raw dev_t can be stored and then human-friendly printed on print time. Both seem about trivial to add. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/