linux-kernel - Re: [PATCH] tracing/lockdep: turn lock->name into an array

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Message-ID: <20090414102754.GH3558@elte.hu>
Date:	Tue, 14 Apr 2009 12:27:54 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Zhaolei <zhaolei@...fujitsu.com>,
	Tom Zanussi <tzanussi@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/lockdep: turn lock->name into an array


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, 2009-04-14 at 00:42 +0200, Frederic Weisbecker wrote:
> > > +#define LOCK_NAME_SIZE       25
> > 
> > 
> > 
> > This constant may look a bit weird.
> > I just started with the assumption that a full lock name
> > will rarely exceed this length.
> > 
> > If you agree with it, I will expand the conversion of lockdep
> > TRACE_FORMAT to TRACE_EVENTS with the same assumption.
> > So that we will be able to use filters with locks events.
> 
> I really really hate this.
> 
> if you pick a size on the top end so that all lock->name's fit in, 
> you're wasting heaps of space, if you pick a median length, 
> everything will get truncated.
> 
> If you're going to do a copy, just do the print into the buffer by 
> using _FORMAT and be done with it.

what i suggested was a variable length field. That solves the size 
issue. The ring-buffer supports variable size records anyway.

	Ingo
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