linux-kernel - Re: [PATCH, RFC 0/3] Improvements to the tracing documentation

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Message-ID: <20090413234741.GI817@elte.hu>
Date:	Tue, 14 Apr 2009 01:47:41 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Theodore Tso <tytso@....edu>, Steven Rostedt <rostedt@...dmis.org>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH, RFC 0/3] Improvements to the tracing documentation


* Theodore Tso <tytso@....edu> wrote:

> On Tue, Apr 14, 2009 at 12:55:42AM +0200, Ingo Molnar wrote:
> > 
> > It could be worked around right now by converting it to an 
> > integer but i think what we want is native support for kdev_t, 
> > together with all the usual convenience forms of specifying it: 
> > sda1 should work the same way as 8:1 or 0801. Even /dev/sda1 
> > should be recognized in a filter expression.
> 
> Yeah, I could just drop in the integer now, and and just have 
> TP_printk() display "(8, 2)" instead of "sda2".  It's really a 
> question of how far we want to take pretty-printing and parsing 
> for ftrace, I suppose.

We try to do it as far as daily use in /debug/tracing/ dictates. 
Interacting with the kernel on such a direct channel is really 
intuitive and useful in debugging and development sessions IMHO.

Raw binary records would encode it in an efficient and 
well-specified manner, so information density is not hurt by 
pretty-printing.

> But if we are going to have end-users use it, having real 
> pretty-printed names would be a good thing, IMHO.  Especially if 
> major/minor numbers start becoming completely random beasts, as 
> some have proposed.  (I think it's a terrible idea, but I'm 
> clearly not politically correct.  :-)

Sounds like a terrible idea to me too. If more space is needed then 
perhaps dynamically allocate the _new_ bits needed - but leave the 
well-established spaces alone. Making everything random looking is 
just asking for all sorts of trouble IMO. Making the system harder 
to understand at a glance, on such a fundamental level, seems silly.

	Ingo
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