From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752418AbeENWVm (ORCPT ); Mon, 14 May 2018 18:21:42 -0400 Received: from mail-pl0-f51.google.com ([209.85.160.51]:45401 "EHLO mail-pl0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752136AbeENWVj (ORCPT ); Mon, 14 May 2018 18:21:39 -0400 X-Google-Smtp-Source: AB8JxZqpTqaobxe+nziCerRfnJ20YSoRk4WVxQcj/clQFMzqMMWuR6ZKqB5gTcTS59aNboMF4EePFg== Date: Tue, 15 May 2018 08:21:20 +1000 From: Nicholas Piggin To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel.opensrc@gmail.com, torvalds@linux-foundation.org, npiggin@gmail.com Subject: Re: [PATCH tip/core/rcu 0/21] Contention reduction for v4.18 Message-ID: <20180515082120.1dbc32b5@roar.ozlabs.ibm.com> In-Reply-To: <20180514160907.GX26088@linux.vnet.ibm.com> References: <20180423030258.GA23370@linux.vnet.ibm.com> <20180514164233.7c7bff00@roar.ozlabs.ibm.com> <20180514160907.GX26088@linux.vnet.ibm.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 14 May 2018 09:09:07 -0700 "Paul E. McKenney" wrote: > On Mon, May 14, 2018 at 04:42:33PM +1000, Nicholas Piggin wrote: > > On Sun, 22 Apr 2018 20:02:58 -0700 > > "Paul E. McKenney" wrote: > > > > > Hello! > > > > > > This series reduces lock contention on the root rcu_node > > > structure, and is also the first precursor to TBD changes to > > > consolidate the three RCU flavors (RCU-bh, RCU-preempt, and > > > RCU-sched) into one. > > > > Hi Paul, > > > > I've been running your rcu/dev branch and haven't noticed any > > problems yet. The irqsoff latency improvement is a little hard to > > measure because the scheduler, but I've tried turning balancing > > parameters right down and I'm yet to see any sign of RCU in traces > > (down to about 100us on a 176 CPU machine), so that's great. > > Good to hear!!! Yep, as in, various other latencies are down to 100us, and still no sign of RCU, so RCU must be sitting somewhere below that. > > (Not that RCU was ever the worst contributor to latency as I said, > > just that I noticed those couple of traces where it showed up.) > > > > Thanks very much for the fast response, sorry I've taken a while to > > test. > > Would you be willing to give me a Tested-by on that series of patches? Yes of course, for your rcu/dev series Tested-by: Nicholas Piggin Let me know if you make any other changes you'd like me to test before merge. Thanks, Nick