Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763307AbZAGWgx (ORCPT ); Wed, 7 Jan 2009 17:36:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932592AbZAGWdq (ORCPT ); Wed, 7 Jan 2009 17:33:46 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:59708 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932586AbZAGWdn (ORCPT ); Wed, 7 Jan 2009 17:33:43 -0500 Date: Wed, 7 Jan 2009 23:33:17 +0100 From: Ingo Molnar To: Gregory Haskins Cc: Andi Kleen , Matthew Wilcox , Linus Torvalds , Steven Rostedt , Peter Zijlstra , paulmck@linux.vnet.ibm.com, Chris Mason , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning Message-ID: <20090107223317.GB27629@elte.hu> References: <1231283778.11687.136.camel@twins> <1231329783.11687.287.camel@twins> <1231347442.11687.344.camel@twins> <20090107210923.GV2002@parisc-linux.org> <20090107213924.GP496@one.firstfloor.org> <49652C7C.3000909@novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49652C7C.3000909@novell.com> User-Agent: Mutt/1.5.18 (2008-05-17) 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: 655 Lines: 20 * Gregory Haskins wrote: > Can I ask a simple question in light of all this discussion? > > "Is get_task_struct() really that bad?" it dirties a cacheline and it also involves atomics. Also, it's a small design cleanliness issue to me: get_task_struct() impacts the lifetime of an object - and if a locking primitive has side-effects on object lifetimes that's never nice. 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/