From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753309Ab2CLRza (ORCPT ); Mon, 12 Mar 2012 13:55:30 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:50458 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499Ab2CLRz3 (ORCPT ); Mon, 12 Mar 2012 13:55:29 -0400 Date: Mon, 12 Mar 2012 10:54:32 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Lai Jiangshan , Lai Jiangshan , 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 Subject: Re: [RFC PATCH 5/6] implement per-cpu&per-domain state machine call_srcu() Message-ID: <20120312175432.GF2471@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com 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> <1331048093.11248.317.camel@twins> <20120308195825.GC2412@linux.vnet.ibm.com> <1331374193.18960.13.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1331374193.18960.13.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12031217-6148-0000-0000-0000042FF7E5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 10, 2012 at 11:09:53AM +0100, Peter Zijlstra wrote: > On Thu, 2012-03-08 at 11:58 -0800, Paul E. McKenney wrote: > > > > But I guess I should ask... Peter, what do you expect the maximum > > call_srcu() rate to be in your use cases? If tens of thousands are > > possible, some adjustments will be needed. > > The one call-site I currently have is linked to vma lifetimes, so yeah, > I guess that that can be lots. So the worst case would be if several processes with lots of VMAs were to exit at about the same time? If so, my guess is that call_srcu() needs to handle several thousand callbacks showing up within a few tens of microseconds. Is that a reasonable assumption, or am I missing an order of magnitude or two in either direction? Thanx, Paul