Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262334AbVCPK0j (ORCPT ); Wed, 16 Mar 2005 05:26:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262335AbVCPK0i (ORCPT ); Wed, 16 Mar 2005 05:26:38 -0500 Received: from mx2.elte.hu ([157.181.151.9]:59030 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S262334AbVCPK0e (ORCPT ); Wed, 16 Mar 2005 05:26:34 -0500 Date: Wed, 16 Mar 2005 11:26:03 +0100 From: Ingo Molnar To: Steven Rostedt Cc: Andrew Morton , rlrevell@joe-job.com, linux-kernel@vger.kernel.org Subject: Re: [patch 0/3] j_state_lock, j_list_lock, remove-bitlocks Message-ID: <20050316102603.GA17847@elte.hu> References: <20050315120053.GA4686@elte.hu> <20050315133540.GB4686@elte.hu> <20050316085029.GA11414@elte.hu> <20050316011510.2a3bdfdb.akpm@osdl.org> <20050316095155.GA15080@elte.hu> <20050316020408.434cc620.akpm@osdl.org> <20050316101209.GA16893@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1428 Lines: 36 * Steven Rostedt wrote: > > > ooh, I'd rather not. I spent an intense three days removing all the > > > sleeping locks from ext3 (and three months debugging the result). > > > Ended up gaining 1000% on 16-way. > > > > > > Putting them back in will really hurt the SMP performance. > > > > ah. Yeah. Sniff. > > > > if we gain 1000% on a 16-way then there's something really wrong about > > semaphores (or scheduling) though. A semaphore is almost a spinlock, in > > the uncontended case - and even under contention we really (should) just > > spend the cycles that we'd spend spinning. There will be some > > intermediate contention level where semaphores hurt, but 1000% sounds > > truly excessive. > > > > Could it possibly be that in the process of removing all the sleeping > locks from ext3, that Andrew also removed a flaw in ext3 itself that > is responsible for the 1000% improvement? i think the chances for that are really remote. I think it must have been a workload ending up scheduling itself to death, while spinlocks force atomicity of execution and affinity. we should be able to see the same scenario with PREEMPT_RT on a 16-way :-) 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/