linux-kernel - Re: [PATCH 03/10] jump label v11: base patch

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Message-ID: <1285082049.23122.1930.camel@gandalf.stny.rr.com>
Date:	Tue, 21 Sep 2010 11:14:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, mathieu.desnoyers@...ymtl.ca, hpa@...or.com,
	tglx@...utronix.de, roland@...hat.com, rth@...hat.com,
	mhiramat@...hat.com, fweisbec@...il.com, avi@...hat.com,
	davem@...emloft.net, vgoyal@...hat.com, sam@...nborg.org,
	tony@...eyournoodle.com
Subject: Re: [PATCH 03/10] jump label v11: base patch

On Tue, 2010-09-21 at 16:41 +0200, Andi Kleen wrote:
> >
> > So there are ~150 tracepoints, but this code is also being proposed for
> > use with 'dynamic debug' of which there are > 1000, and I'm hoping for
> > more users moving forward.
> 
> Even 1000 is fine to walk, but if it was sorted a binary search
> would be much faster anyways. That is then you would still
> need to search for each module, but that is a relatively small
> number (< 100)

xfs has > 100 tracepoints

> 
> > Also, I think the hash table deals nicely with modules.
> 
> Maybe but it's also a lot of code. And it seems to me
> that it is optimizing the wrong thing. Simpler is nicer.

I guess simplicity is in the eye of the beholder. I find hashes easier
to deal with than binary searching sorted lists. Every time you add a
tracepoint, you need to resort the list.

Hashes are much easier to deal with and scale nicely. I don't think
there's enough rational to switch this to a binary list.

-- Steve


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