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

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Date:	Tue, 21 Sep 2010 19:42:02 +0200
From:	"Andi Kleen" <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Jason Baron" <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, mathieu.desnoyers@...ymtl.ca, 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

>
> If all you need is exact matches -- as in this case -- hashes are
> generally faster than binary anyway.

Actually only if you have the whole thing in cache. The binary
search has a much nicer access pattern if it's cache cold.

And the footprint of directly accessing the section than having
separate large list and tables is also significantly more
compared to a compact table.

But I don't think the access speed really matters here. Toggling
trace points should be rare and is not a critical path
operation. What matters is runtime overhead and simplicity.

Right now on the simplicity front there is a problem.

-Andi

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