From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755560AbaGBRzN (ORCPT ); Wed, 2 Jul 2014 13:55:13 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:44748 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbaGBRzL (ORCPT ); Wed, 2 Jul 2014 13:55:11 -0400 Date: Wed, 2 Jul 2014 10:55:01 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, riel@redhat.com, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, sbw@mit.edu Subject: Re: [PATCH RFC tip/core/rcu] Parallelize and economize NOCB kthread wakeups Message-ID: <20140702175501.GW4603@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140627142038.GA22942@linux.vnet.ibm.com> <20140702123412.GD19379@twins.programming.kicks-ass.net> <20140702153915.GQ4603@linux.vnet.ibm.com> <20140702160412.GO19379@twins.programming.kicks-ass.net> <20140702170838.GS4603@linux.vnet.ibm.com> <20140702172600.GR19379@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140702172600.GR19379@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14070217-8236-0000-0000-0000038CE281 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 02, 2014 at 07:26:00PM +0200, Peter Zijlstra wrote: > On Wed, Jul 02, 2014 at 10:08:38AM -0700, Paul E. McKenney wrote: > > As were others, not that long ago. Today is the first hint that I got > > that you feel otherwise. But it does look like the softirq approach to > > callback processing needs to stick around for awhile longer. Nice to > > hear that softirq is now "sane and normal" again, I guess. ;-) > > Nah, softirqs are still totally annoying :-) Name me one thing that isn't annoying. ;-) > So I've lost detail again, but it seems to me that on all CPUs that are > actually getting ticks, waking tasks to process the RCU state is > entirely over doing it. Might as well keep processing their RCU state > from the tick as was previously done. And that is in fact the approach taken by my patch. For which I just kicked off testing, so expect an update later today. (And that -is- optimistic! A pessimistic viewpoint would hold that the patch would turn out to be so broken that it would take -weeks- to get a fix!) Thanx, Paul