Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262044AbVCTIBj (ORCPT ); Sun, 20 Mar 2005 03:01:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261433AbVCTIBi (ORCPT ); Sun, 20 Mar 2005 03:01:38 -0500 Received: from smtpout.mac.com ([17.250.248.88]:40925 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S262044AbVCTIBb (ORCPT ); Sun, 20 Mar 2005 03:01:31 -0500 In-Reply-To: <20050319163128.GB28958@elte.hu> References: <20050318160229.GC25485@elte.hu> <20050319163128.GB28958@elte.hu> Mime-Version: 1.0 (Apple Message framework v619.2) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <24e1c77a699dcab771a0280df69d44eb@mac.com> Content-Transfer-Encoding: 7bit Cc: Herbert Xu , rusty@au1.ibm.com, bhuey@lnxw.com, gh@us.ibm.com, tgall@us.ibm.com, jim.houston@comcast.net, linux-kernel@vger.kernel.org, torvalds@osdl.org, akpm@osdl.org, paulmck@us.ibm.com, manfred@colorfullife.com, shemminger@osdl.org, dipankar@in.ibm.com From: Kyle Moffett Subject: Re: Real-Time Preemption and RCU Date: Sun, 20 Mar 2005 03:01:11 -0500 To: Ingo Molnar X-Mailer: Apple Mail (2.619.2) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1145 Lines: 31 On Mar 19, 2005, at 11:31, Ingo Molnar wrote: >> What about allowing only as many concurrent readers as there are CPUs? > > since a reader may be preempted by a higher prio task, there is no > linear relationship between CPU utilization and the number of readers > allowed. You could easily end up having all the nr_cpus readers > preempted on one CPU. It gets pretty messy One solution I can think of, although it bloats memory usage for many-way boxen, is to just have a table in the rwlock with one entry per cpu. Each CPU would get one concurrent reader, others would need to sleep Cheers, Kyle Moffett -----BEGIN GEEK CODE BLOCK----- Version: 3.12 GCM/CS/IT/U d- s++: a18 C++++>$ UB/L/X/*++++(+)>$ P+++(++++)>$ L++++(+++) E W++(+) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+ PGP+++ t+(+++) 5 X R? tv-(--) b++++(++) DI+ D+ G e->++++$ h!*()>++$ r !y?(-) ------END GEEK CODE BLOCK------ - 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/