From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756282AbXGHHvv (ORCPT ); Sun, 8 Jul 2007 03:51:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752760AbXGHHvm (ORCPT ); Sun, 8 Jul 2007 03:51:42 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40912 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752629AbXGHHvl (ORCPT ); Sun, 8 Jul 2007 03:51:41 -0400 Date: Sun, 8 Jul 2007 09:51:19 +0200 From: Ingo Molnar To: Christoph Lameter Cc: linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org, suresh.b.siddha@intel.com, corey.d.gough@intel.com, Pekka Enberg , akpm@linux-foundation.org, Matt Mackall Subject: Re: [patch 09/10] Remove the SLOB allocator for 2.6.23 Message-ID: <20070708075119.GA16631@elte.hu> References: <20070708034952.022985379@sgi.com> <20070708035018.074510057@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070708035018.074510057@sgi.com> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org (added Matt to the Cc: list) * Christoph Lameter wrote: > Maintenance of slab allocators becomes a problem as new features for > allocators are developed. The SLOB allocator in particular has been > lagging behind in many ways in the past: > > - Had no support for SLAB_DESTROY_BY_RCU for years (but no one > noticed) > > - Still has no support for slab reclaim counters. This may currently > not be necessary if one would restrict the supported configurations > for functionality relying on these. But even that has not been done. > > The only current advantage over SLUB in terms of memory savings is > through SLOBs kmalloc layout that is not power of two based like SLAB > and SLUB which allows to eliminate some memory waste. > > Through that SLOB has still a slight memory advantage over SLUB of > ~350k in for a standard server configuration. It is likely that the > savings are is smaller for real embedded configurations that have less > functionality. actually, one real advantage of the SLOB is that it is a minimal, really simple allocator. Its text and data size is so small as well. here's the size comparison: text data bss dec hex filename 10788 837 16 11641 2d79 mm/slab.o 6205 4207 124 10536 2928 mm/slub.o 1640 44 4 1688 698 mm/slob.o slab/slub have roughly the same footprint, but slob is 10% of that size. Would be a waste to throw this away. A year ago the -rt kernel defaulted to the SLOB for a few releases, and barring some initial scalability issues (which were solved in -rt) it worked pretty well on generic PCs, so i dont buy the 'it doesnt work' argument either. Ingo