Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030245AbVLSEXE (ORCPT ); Sun, 18 Dec 2005 23:23:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030248AbVLSEXE (ORCPT ); Sun, 18 Dec 2005 23:23:04 -0500 Received: from mx2.suse.de ([195.135.220.15]:10442 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S1030245AbVLSEXC (ORCPT ); Sun, 18 Dec 2005 23:23:02 -0500 Date: Mon, 19 Dec 2005 05:22:48 +0100 From: Andi Kleen To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Arjan van de Ven , Steven Rostedt , Alan Cox , Christoph Hellwig , Andi Kleen , David Howells , Alexander Viro , Oleg Nesterov Subject: Re: [patch 00/15] Generic Mutex Subsystem Message-ID: <20051219042248.GG23384@wotan.suse.de> References: <20051219013415.GA27658@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051219013415.GA27658@elte.hu> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1429 Lines: 29 > $ ./test-mutex V 16 10 $ ./test-mutex V 16 10 > 8 CPUs, running 16 tasks. 8 CPUs, running 16 tasks. > checking VFS performance. checking VFS performance. > avg loops/sec: 34713 avg loops/sec: 84153 > CPU utilization: 63% CPU utilization: 22% > > i.e. in this workload, the mutex based kernel was 2.4 times faster > than the semaphore based kernel, _and_ it also had 2.8 times less CPU > utilization. (In terms of 'ops per CPU cycle', the semaphore kernel > performed 551 ops/sec per 1% of CPU time used, while the mutex kernel > performed 3825 ops/sec per 1% of CPU time used - it was 6.9 times > more efficient.) Do you have an idea where this big difference comes from? It doesn't look it's from the fast path which is essentially the same. Do the mutexes have that much better scheduling behaviour than semaphores? It is a bit hard to believe. I would perhaps understand your numbers if you used adaptive mutexes or similar that spin for a bit, but just for pure sleeping locks it seems weird. After all the scheduler should work in the same way for both. -Andi - 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/