Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758531AbYG3Wju (ORCPT ); Wed, 30 Jul 2008 18:39:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753461AbYG3Wjm (ORCPT ); Wed, 30 Jul 2008 18:39:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:54614 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753425AbYG3Wjm (ORCPT ); Wed, 30 Jul 2008 18:39:42 -0400 Date: Wed, 30 Jul 2008 15:35:58 -0700 (PDT) From: Linus Torvalds To: Pekka Enberg cc: Matt Mackall , Christoph Lameter , Ingo Molnar , Hugh Dickins , Andi Kleen , Peter Zijlstra , Linux Kernel Mailing List , vegard.nossum@gmail.com, hannes@saeurebad.de Subject: Re: [RFC PATCH] greatly reduce SLOB external fragmentation In-Reply-To: <84144f020807301522r7fb97bfehe0fcdceef10477b9@mail.gmail.com> Message-ID: References: <1199906151.6245.57.camel@cinder.waste.org> <1199919548.6245.74.camel@cinder.waste.org> <84144f020807301522r7fb97bfehe0fcdceef10477b9@mail.gmail.com> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1463 Lines: 34 On Thu, 31 Jul 2008, Pekka Enberg wrote: > > Oh, I didn't suggest this for merging. Just thought you'd be > interested to know that best-fit doesn't really do that much better > than what we have in the tree now. (Well, I was kinda hoping you'd > tell me why my implementation is wrong and you were right all along.) Heh. Most allocators tend to work pretty well under normal load, and the real fragmentation problems all tend to happen under special patterns. The one in glibc, for example, sucks donkey dick when using threading, but is apparently ok otherwise. I wouldn't actually expect most "normal" kernel use to show any really bad patterns on any normal loads. Google for worst-case first-fit fragmentation (or 'next-fit' for that matter) to see some stuff. Of course, it is scary only if you can trigger it in practice (perhaps with certains games on packet size, or creating/removing files with pathname size patterns ec). [ Of course, google probably mostly returns hits from all those ACM portals etc. I wonder why google does that - they're almost totally useless search results. Sad. If somebody knows how to turn those ACM pay-portals off in google, pls let me know ] Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/