Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751193AbWH1Qnl (ORCPT ); Mon, 28 Aug 2006 12:43:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751200AbWH1Qnl (ORCPT ); Mon, 28 Aug 2006 12:43:41 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:36757 "EHLO e6.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1751193AbWH1Qnk (ORCPT ); Mon, 28 Aug 2006 12:43:40 -0400 Date: Mon, 28 Aug 2006 22:13:45 +0530 From: Dipankar Sarma To: Arjan van de Ven Cc: Paul E McKenney , Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/4] RCU: various merge candidates Message-ID: <20060828164345.GH3325@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20060828160845.GB3325@in.ibm.com> <1156781748.3034.212.camel@laptopd505.fenrus.org> <20060828162904.GG3325@in.ibm.com> <1156782789.3034.216.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1156782789.3034.216.camel@laptopd505.fenrus.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1347 Lines: 36 On Mon, Aug 28, 2006 at 06:33:09PM +0200, Arjan van de Ven wrote: > On Mon, 2006-08-28 at 21:59 +0530, Dipankar Sarma wrote: > > On Mon, Aug 28, 2006 at 06:15:48PM +0200, Arjan van de Ven wrote: > > > On Mon, 2006-08-28 at 21:38 +0530, Dipankar Sarma wrote: > > Hi Arjan, > > > > See this for a background - http://lwn.net/Articles/129511/ > > > > Primarily, rcupreempt allows read-side critical sections to > > be preempted unline classic RCU currently in mainline. It is > > also a bit more aggressive in terms of grace periods by counting > > the number of readers as opposed to periodic checks in classic > > RCU. > > > > hi, > > thanks for the explenation, this for sure explains one half of the > equation; the other half is ... "why do we not always want this"? It comes with read-side overheads for keeping track of critical sections and we need to carefully check its impact on performance over a more wide variety of workload before deciding to switch the default. See table 2 of page 10 in this paper - http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf Thanks Dipankar - 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/