From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030919Ab2CFPf2 (ORCPT ); Tue, 6 Mar 2012 10:35:28 -0500 Received: from merlin.infradead.org ([205.233.59.134]:41756 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030792Ab2CFPf1 convert rfc822-to-8bit (ORCPT ); Tue, 6 Mar 2012 10:35:27 -0500 Message-ID: <1331048093.11248.317.camel@twins> Subject: Re: [RFC PATCH 5/6] implement per-cpu&per-domain state machine call_srcu() From: Peter Zijlstra To: Lai Jiangshan Cc: Lai Jiangshan , "Paul E. McKenney" , linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, tj@kernel.org Date: Tue, 06 Mar 2012 16:34:53 +0100 In-Reply-To: References: <1331023359-6987-1-git-send-email-laijs@cn.fujitsu.com> <1331027858-7648-1-git-send-email-laijs@cn.fujitsu.com> <1331027858-7648-5-git-send-email-laijs@cn.fujitsu.com> <1331032571.11248.277.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-03-06 at 23:12 +0800, Lai Jiangshan wrote: > On Tue, Mar 6, 2012 at 7:16 PM, Peter Zijlstra wrote: > > On Tue, 2012-03-06 at 17:57 +0800, Lai Jiangshan wrote: > >> srcu_head is bigger, it is worth, it provides more ability and simplify > >> the srcu code. > > > > Dubious claim.. memory footprint of various data structures is deemed > > important. rcu_head is 16 bytes, srcu_head is 32 bytes. I think it would > > be real nice not to have two different callback structures and not grow > > them as large. > > CC: tj@kernel.org > It could be better if workqueue also supports 2*sizeof(long) work callbacks. That's going to be very painful if at all possible. > I prefer ability/functionality a little more, it eases the caller's pain. > preemptible callbacks also eases the pressure of the whole system. > But I'm also ok if we limit the srcu-callbacks in softirq. You don't have to use softirq, you could run a complete list from a single worklet. Just keep the single linked rcu_head list and enqueue a static (per-cpu) worker to process the entire list.