From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757281AbcATSoV (ORCPT ); Wed, 20 Jan 2016 13:44:21 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:56713 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752687AbcATSoT (ORCPT ); Wed, 20 Jan 2016 13:44:19 -0500 Date: Wed, 20 Jan 2016 19:44:14 +0100 From: Peter Zijlstra To: Nicolas Pitre Cc: Daniel Lezcano , tglx@linutronix.de, rafael@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, vincent.guittot@linaro.org Subject: Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period Message-ID: <20160120184414.GQ6357@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 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 20, 2016 at 12:46:48PM -0500, Nicolas Pitre wrote: > > +struct stats { > > + u64 sum; /* sum of values */ > > + u32 values[STATS_NR_VALUES]; /* array of values */ > > + unsigned char w_ptr; /* current window pointer */ > > Why did you change this from an unsigned int? > > This won't provide any memory space saving given that the structure has > to be padded up to the next 64-bit boundary. Not to mention that loading bytes is more expensive on many archs compared to full words. Also, its not a pointer, its an index. So: unsigned int w_idx;