From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261347AbVA1A4K (ORCPT ); Thu, 27 Jan 2005 19:56:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261343AbVA1A4J (ORCPT ); Thu, 27 Jan 2005 19:56:09 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:56291 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S261347AbVA1Axs (ORCPT ); Thu, 27 Jan 2005 19:53:48 -0500 Date: Thu, 27 Jan 2005 16:53:30 -0800 From: Paul Jackson To: Linus Torvalds Cc: mingo@elte.hu, pwil3058@bigpond.net.au, akpm@osdl.org, linux-kernel@vger.kernel.org Subject: Re: [patch, 2.6.10-rc2] sched: fix ->nr_uninterruptible handling bugs Message-Id: <20050127165330.6f388054.pj@sgi.com> In-Reply-To: References: <20041116113209.GA1890@elte.hu> <419A7D09.4080001@bigpond.net.au> <20041116232827.GA842@elte.hu> Organization: SGI X-Mailer: Sylpheed version 0.9.12 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org A long time ago, Linus wrote: > An atomic op is pretty much as expensive as a spinlock/unlock pair on x86. > Not _quite_, but it's pretty close. Are both read and modify atomic ops relatively expensive on some CPUs, or is it just modify atomic ops? (Ignoring for this question the possibility that a mix of read and modify ops could heat up a cache line on multiprocessor systems, and focusing for the moment just on the CPU internals ...) -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.650.933.1373, 1.925.600.0401