Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754650AbXLVTag (ORCPT ); Sat, 22 Dec 2007 14:30:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752841AbXLVTa3 (ORCPT ); Sat, 22 Dec 2007 14:30:29 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:36989 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785AbXLVTa2 (ORCPT ); Sat, 22 Dec 2007 14:30:28 -0500 Date: Sat, 22 Dec 2007 20:29:57 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Andi Kleen , Christoph Lameter , Peter Zijlstra , Steven Rostedt , LKML , Andrew Morton , Christoph Hellwig , "Rafael J. Wysocki" Subject: Re: Major regression on hackbench with SLUB (more numbers) Message-ID: <20071222192957.GA6646@elte.hu> References: <1198275391.30889.3.camel@lappy> <1198275453.30889.4.camel@lappy> <20071221225413.GA26189@elte.hu> <20071222100326.GF26157@elte.hu> <20071222190933.GA2958@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071222190933.GA2958@elte.hu> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2479 Lines: 60 * Ingo Molnar wrote: > I'd also not rely on the fact that only a few people are complaining. > Most people, even 2.6.24-rc early adopters, still use SLAB because > early adopters typically use their .23 .config and do a 'make > oldconfig' - which picks up SLAB. So SLUB use will become more > widespread only once 2.6.24 is out and is packaged in distros. Distros > will likely pick SLUB if there's no performance worries and if it's > the default. Fedora rawhide already uses SLUB. here's some silly statistics about allocator coverage on lkml, based on configs reported to lkml in the past 4 months: $ for N in SLAB SLUB SLOB; do printf "%s: " $N; grep ^CONFIG_$N=y linux-kernel | wc -l; done SLAB: 70 SLUB: 77 SLOB: 4 so SLUB and SLAB is utilized about equally amongst people who reported configs to lkml. But people who use SLUB enabled it intentionally - and they are thus much less likely to complain about this choice of them. Reporting: "I just enabled SLUB instead of SLAB, and hey guys, it does not have SLABinfo" has a foolish ring to it, doesnt it? I'd rather ask carefully, like this person did: http://kerneltrap.org/mailarchive/linux-kernel/2007/10/12/335765 This is one of the reasons why i think the whole SLAB->SLUB renaming was bad - we should have done SLAB2 or SLAB^2 instead, so that people expect _at least as good_ behavior (performance, features, etc.) from SLUB as from SLAB. Instead of "something different". anyway ... i think we still generally suck _alot_ at providing near-transparent kernel upgrades to users. (kernel upgrades are still a pain and risk, and often just due to poor developer choices on our side.) It's nowhere near as bad as the 2.4->2.6 transition was (in fact it shouldnt even be mentioned in the same sentence), and it's getting better gradually, but i think we should just by default be 10 times more careful about these things - whenever it is borderline technically sane to do so. We induce enough unintentional breakage of user-space, we shouldnt compound it with intentional breakages. The kernel community still has _a lot_ of user and distro trust to win back. So being seen as over-cautious wont harm. Ingo -- 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/