From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 3/4 RFC] RCU: preemptible RCU Date: Tue, 7 Aug 2007 22:32:56 -0700 Message-ID: <20070808053256.GA5024@linux.vnet.ibm.com> References: <20070807183946.GA32110@linux.vnet.ibm.com> <20070807184812.GC10068@linux.vnet.ibm.com> <1186514309.11797.171.camel@lappy> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, mingo@elte.hu, akpm@linux-foundation.org, dipankar@in.ibm.com, josht@linux.vnet.ibm.com, tytso@us.ibm.com, dvhltc@us.ibm.com, tglx@linutronix.de To: Peter Zijlstra Return-path: Received: from e4.ny.us.ibm.com ([32.97.182.144]:32868 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934869AbXHHFdD (ORCPT ); Wed, 8 Aug 2007 01:33:03 -0400 Content-Disposition: inline In-Reply-To: <1186514309.11797.171.camel@lappy> Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Tue, Aug 07, 2007 at 09:18:29PM +0200, Peter Zijlstra wrote: > On Tue, 2007-08-07 at 11:48 -0700, Paul E. McKenney wrote: > > This patch implements a new version of RCU which allows its read-side > > critical sections to be preempted. It uses a set of counter pairs > > to keep track of the read-side critical sections and flips them > > when all tasks exit read-side critical section. The details > > of this implementation can be found in this paper - > > > > http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf > > > > This patch was developed as a part of the -rt kernel development and > > meant to provide better latencies when read-side critical sections of > > RCU don't disable preemption. As a consequence of keeping track of RCU > > readers, the readers have a slight overhead (optimizations in the paper). > > This implementation co-exists with the "classic" RCU implementations > > and can be switched to at compiler. > > > > Also includes RCU tracing summarized in debugfs and RCU_SOFTIRQ for > > the preemptible variant of RCU. > > Whickedly complex but very cool stuff! > > Unfortunately I have nothing to contribute other than praise at the > complex yet elegant way you dodged the need for synchronisation. I am glad you like it! Heck, I may have to print this email out, frame it, and hang it on my cube wall. ;-) Thanx, Paul