From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932827AbcAaCwa (ORCPT ); Sat, 30 Jan 2016 21:52:30 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:36174 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932570AbcAaCw2 (ORCPT ); Sat, 30 Jan 2016 21:52:28 -0500 Message-ID: <1454208745.3688.14.camel@gmail.com> Subject: Re: [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy From: Mike Galbraith To: Frederic Weisbecker Cc: Rik van Riel , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, luto@amacapital.net, Clark Williams Date: Sun, 31 Jan 2016 03:52:25 +0100 In-Reply-To: <20160130203602.GA7856@lerouge> References: <1454106180-20918-1-git-send-email-riel@redhat.com> <1454106180-20918-3-git-send-email-riel@redhat.com> <56ABEB10.5060307@redhat.com> <20160130142037.GA32581@lerouge> <1454176385.3797.23.camel@gmail.com> <20160130203602.GA7856@lerouge> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2016-01-30 at 21:36 +0100, Frederic Weisbecker wrote: > On Sat, Jan 30, 2016 at 06:53:05PM +0100, Mike Galbraith wrote: > > On Sat, 2016-01-30 at 15:20 +0100, Frederic Weisbecker wrote: > > > On Fri, Jan 29, 2016 at 05:43:28PM -0500, Rik van Riel wrote: > > > > > > Run times for the microbenchmark: > > > > > > > > 4.4 3.8 seconds > > > > 4.5-rc1 3.7 seconds > > > > 4.5-rc1 + first patch 3.3 seconds > > > > 4.5-rc1 + both patches 2.3 seconds > > > > > > Very nice improvement! > > > > Tasty indeed. > > > > When nohz_full CPUs are not isolated, ie are being used as generic > > CPUs, get_nohz_timer_target() is a problem with things like tbench. > > So by isolated CPU you mean those part of isolcpus= boot option, > right? Yes, isolated in the scheduler sense, either via isolcpus= or cpusets. If the CPU is part of a scheduler domain, it is by definition part of the generic work crew. > > tbench 8 with Rik's patches applied: > > nohz_full=empty > > Throughput 3204.69 MB/sec 1.000 > > nohz_full=1-3,5-7 > > Throughput 1354.99 MB/sec .422 1.000 > > nohz_full=1-3,5-7 + club below > > Throughput 2762.22 MB/sec .861 2.038 > > > > With Rik's patches and a club, tbench becomes nearly acceptable. > > --- > > include/linux/tick.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > --- a/include/linux/tick.h > > +++ b/include/linux/tick.h > > @@ -184,7 +184,7 @@ static inline const struct cpumask *hous > > static inline bool is_housekeeping_cpu(int cpu) > > { > > #ifdef CONFIG_NO_HZ_FULL > > - if (tick_nohz_full_enabled()) > > + if (tick_nohz_full_enabled() && runqueue_is_isolated(cpu)) > > return cpumask_test_cpu(cpu, housekeeping_mask); > > This makes me confused. How forcing timers to CPUs in isolcpus is making > better results? It doesn't, it's shutting get_nohz_timer_target() down for those nohz_full CPUs that are NOT currently isolated, are thus generic CPUs with the capability to _become_ elite solo artists on demand. -Mike