linux-kernel - Re: [patch 1/2] infrastructure to debug (dynamic) objects

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Message-Id: <1204411377.6240.13.camel@lappy>
Date:	Sat, 01 Mar 2008 23:42:57 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Greg KH <greg@...ah.com>
Subject: Re: [patch 1/2] infrastructure to debug (dynamic) objects


On Sat, 2008-03-01 at 12:44 +0100, Thomas Gleixner wrote:
> On Sat, 1 Mar 2008, Andrew Morton wrote:

> > > +
> > > +#define ODEBUG_HASH_SIZE	4096
> > 
> > power-of-2 is said to be a very poor size for a hash table.
> 
> The hash is not a randomized hash as one would expect. It's purely
> generated from the object address to simplify the lookup during the
> free check. So the power of 2 size is a good thing :) /me adds
> comment.

Power of two buckets work when used along with a golden ratio based hash
map - as done by linux/hash.h.

Power of two hash maps otoh suck royally.

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