From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754565AbbGBCSv (ORCPT ); Wed, 1 Jul 2015 22:18:51 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:49996 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754493AbbGBCSn (ORCPT ); Wed, 1 Jul 2015 22:18:43 -0400 X-Helo: d03dlp01.boulder.ibm.com X-MailFrom: paulmck@linux.vnet.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Date: Wed, 1 Jul 2015 19:18:38 -0700 From: "Paul E. McKenney" To: Mike Galbraith Cc: josh@joshtriplett.org, Peter Zijlstra , linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging normal ones Message-ID: <20150702021838.GA3717@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150630221224.GQ3717@linux.vnet.ibm.com> <20150630234633.GA11450@cloud> <20150701100939.GR19282@twins.programming.kicks-ass.net> <20150701105511.GN18673@twins.programming.kicks-ass.net> <20150701140031.GB3717@linux.vnet.ibm.com> <20150701141710.GG25159@twins.programming.kicks-ass.net> <20150701161705.GK3717@linux.vnet.ibm.com> <1435799484.3482.15.camel@gmail.com> <20150702013426.GB19350@cloud> <1435802395.6887.20.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1435802395.6887.20.camel@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15070202-0025-0000-0000-0000104E3E3F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 02, 2015 at 03:59:55AM +0200, Mike Galbraith wrote: > On Wed, 2015-07-01 at 18:34 -0700, josh@joshtriplett.org wrote: > > On Thu, Jul 02, 2015 at 03:11:24AM +0200, Mike Galbraith wrote: > > > On Wed, 2015-07-01 at 09:17 -0700, Paul E. McKenney wrote: > > > > On Wed, Jul 01, 2015 at 04:17:10PM +0200, Peter Zijlstra wrote: > > > > > On Wed, Jul 01, 2015 at 07:00:31AM -0700, Paul E. McKenney wrote: > > > > > > > > > > > That is a bit extreme, Peter. > > > > > > > > > > Of course; but I'm really not seeing people taking due care with them > > > > > > > > ;-) > > > > > > > > > > Are a huge pile of them coming in this merge window or something? > > > > > > What raised your concerns on this issue? > > > > > > > > > > This is complete horse manure (breaking the nvidiot binary blob is a > > > > > good thing): > > > > > > > > > > 74b51ee152b6 ("ACPI / osl: speedup grace period in acpi_os_map_cleanup") > > > > > > > > Really??? > > > > > > > > I am not concerned about this one. After all, one of the first things > > > > that people do for OS-jitter-sensitive workloads is to get rid of > > > > binary blobs. > > > > > > I know two users who have no choice but to use the nvidia driver with > > > their realtime applications, as nouveau is not up to the task. > > > > Sounds like they have a relatively loose definition of "realtime", then. > > It would be better it they broke their beasts up into a bunch of small > synchronized boxen, but they use big boxen here and now, with realtime > rendering being a non-disposable portion of the load. Does their normal workload trigger the condition that results in the expedited grace period? If so, do they use NO_HZ_FULL? (I am guessing "no".) If not, is the resulting double-context-switch on their worker CPUs a real problem for them? (I am guessing "no" given that they have not complained, at least not that I know of.) Thanx, Paul