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Date: Tue, 30 Sep 2008 16:01:12 -0400
From: "Frank Ch. Eigler" <fche@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Martin Bligh <mbligh@google.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org,
       prasad@linux.vnet.ibm.com,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, od@suse.com,
       Andrew Morton <akpm@linux-foundation.org>, hch@lst.de,
       David Wilder <dwilder@us.ibm.com>, Tom Zanussi <zanussi@comcast.net>
Subject: Re: [RFC PATCH] LTTng relay buffer allocation, read, write
Message-ID: <20080930200112.GD27822@redhat.com>
References: <20080929155004.GA11029@Krystal> <1222709445.23876.70.camel@twins.programming.kicks-ass.net> <20080929203124.GA23070@Krystal> <alpine.DEB.1.10.0809291643570.8145@gandalf.stny.rr.com> <33307c790809301022q2821ecc7iabf41eb513707e0c@mail.gmail.com> <33307c790809301023v1b0755fbsab1bbfa9bfaad58@mail.gmail.com> <20080930181436.GA19690@Krystal> <alpine.DEB.1.10.0809301421330.6224@gandalf.stny.rr.com> <20080930183531.GA20670@Krystal> <alpine.DEB.1.10.0809301541120.7993@gandalf.stny.rr.com>
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Hi -

On Tue, Sep 30, 2008 at 03:43:45PM -0400, Steven Rostedt wrote:
> [...]
> On Tue, 30 Sep 2008, Mathieu Desnoyers wrote:
> > 
> > You are actually using them to put redundant information that could be
> > encoded differently and thus save 4 bits per event records, more or less
> > what will be needed by most tracers (15 IDs, 1 reserved for an extended
> > ID field).
> 
> I really like the idea of keeping the tracer event ids out of the ring 
> buffer logic.

That's fine for a ring buffer that only ever contains data from one
event source.  How do you imagine multiplexing working, where one
wants to grep a single debugfs file that contains data from different
event sources?  Punt to another layer?

- FChE