From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758761AbYCAWn2 (ORCPT ); Sat, 1 Mar 2008 17:43:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754589AbYCAWnS (ORCPT ); Sat, 1 Mar 2008 17:43:18 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:43663 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754833AbYCAWnS (ORCPT ); Sat, 1 Mar 2008 17:43:18 -0500 Subject: Re: [patch 1/2] infrastructure to debug (dynamic) objects From: Peter Zijlstra To: Thomas Gleixner Cc: Andrew Morton , LKML , Ingo Molnar , Greg KH In-Reply-To: References: <20080301100019.640027768@linutronix.de> <20080301100325.593267564@linutronix.de> <20080301025134.d9c74110.akpm@linux-foundation.org> Content-Type: text/plain Date: Sat, 01 Mar 2008 23:42:57 +0100 Message-Id: <1204411377.6240.13.camel@lappy> Mime-Version: 1.0 X-Mailer: Evolution 2.21.90 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.