From mboxrd@z Thu Jan 1 00:00:00 1970 From: Darren Hart Subject: Re: [RFC patch] introduce sys_membarrier(): process-wide memory barrier (v9) Date: Wed, 24 Feb 2010 09:29:46 -0800 Message-ID: <4B85620A.7000901@us.ibm.com> References: <20100212224606.GA30280@Krystal> <4B82CF1A.3010501@nortel.com> <20100222212321.GA2573@Krystal> <20100224091052.GY9738@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from e37.co.us.ibm.com ([32.97.110.158]:37720 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757273Ab0BXRaN (ORCPT ); Wed, 24 Feb 2010 12:30:13 -0500 In-Reply-To: <20100224091052.GY9738@laptop> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Nick Piggin Cc: Mathieu Desnoyers , Chris Friesen , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, KOSAKI Motohiro , Steven Rostedt , "Paul E. McKenney" , Nicholas Miell , Linus Torvalds , mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com Nick Piggin wrote: > When writing multiprocessor scalable software, threads should often be > avoided. They share so much state that it is easy to run into > scalability issues in the kernel. So yes it would be really nice to > have userspace RCU available in a process-shared mode. A bit off topic, but I'm interested in what you feel some of these scalability issues are. Is it mostly bouncing this shared context from one CPU to the next and the related cache effects, or is there something more you are referring to? -- Darren Hart IBM Linux Technology Center Real-Time Linux Team