From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752308AbcFNP7E (ORCPT ); Tue, 14 Jun 2016 11:59:04 -0400 Received: from merlin.infradead.org ([205.233.59.134]:36502 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbcFNP7C (ORCPT ); Tue, 14 Jun 2016 11:59:02 -0400 Date: Tue, 14 Jun 2016 17:58:42 +0200 From: Peter Zijlstra To: Frederic Weisbecker Cc: LKML , Ingo Molnar , Mike Galbraith , Thomas Gleixner Subject: Re: [PATCH 2/3] sched: Unloop sched avg decaying Message-ID: <20160614155842.GJ30921@twins.programming.kicks-ass.net> References: <1465918082-27005-1-git-send-email-fweisbec@gmail.com> <1465918082-27005-3-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1465918082-27005-3-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 14, 2016 at 05:28:01PM +0200, Frederic Weisbecker wrote: > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 385c947..0c0578a 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -666,17 +666,17 @@ bool sched_can_stop_tick(struct rq *rq) > void sched_avg_update(struct rq *rq) > { > s64 period = sched_avg_period(); > + s64 delta; > + u64 rem; > + int pending; > > + delta = (s64)(rq_clock(rq) - rq->age_stamp); > + if (delta <= period) > + return; > + > + pending = div64_u64_rem(delta, period, &rem); > + rq->age_stamp += delta - rem; > + rq->rt_avg >>= pending; > } Blergh, and now do the profile on machine that doesn't have major transistor count dedicated to divisions. Why not add the division to the nohz exit path only?