From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period Date: Wed, 20 Jan 2016 20:40:06 +0100 Message-ID: <20160120194006.GW6357@twins.programming.kicks-ass.net> References: <1453305636-22156-1-git-send-email-daniel.lezcano@linaro.org> <1453305636-22156-3-git-send-email-daniel.lezcano@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bombadil.infradead.org ([198.137.202.9]:60498 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751194AbcATTkK (ORCPT ); Wed, 20 Jan 2016 14:40:10 -0500 Content-Disposition: inline In-Reply-To: <1453305636-22156-3-git-send-email-daniel.lezcano@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Daniel Lezcano Cc: tglx@linutronix.de, rafael@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, nicolas.pitre@linaro.org, vincent.guittot@linaro.org On Wed, Jan 20, 2016 at 05:00:33PM +0100, Daniel Lezcano wrote: > +static inline u32 stats_mean(struct stats *s) > +{ > + /* > + * gcc is smart enough to convert to a bits shift when the > + * divisor is constant and multiple of 2^x. > + * > + * The number of values could have not reached STATS_NR_VALUES > + * yet, but we can consider it acceptable as the situation is > + * only at the beginning of the burst of irqs. > + */ > + return s->sum / STATS_NR_VALUES; > +} Note that ->sum is u64, so you're very prone to truncation.