From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754712AbaE1PRl (ORCPT ); Wed, 28 May 2014 11:17:41 -0400 Received: from casper.infradead.org ([85.118.1.10]:43320 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754058AbaE1PRj (ORCPT ); Wed, 28 May 2014 11:17:39 -0400 Date: Wed, 28 May 2014 17:17:30 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: Vincent Guittot , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "linux@arm.linux.org.uk" , "linux-arm-kernel@lists.infradead.org" , "preeti@linux.vnet.ibm.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , "linaro-kernel@lists.linaro.org" , "daniel.lezcano@linaro.org" Subject: Re: [PATCH v2 08/11] sched: get CPU's activity statistic Message-ID: <20140528151730.GW11096@twins.programming.kicks-ass.net> References: <1400860385-14555-1-git-send-email-vincent.guittot@linaro.org> <1400860385-14555-9-git-send-email-vincent.guittot@linaro.org> <20140528121001.GI19967@e103034-lin> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="EzoGi9kFQAnUjl0a" Content-Disposition: inline In-Reply-To: <20140528121001.GI19967@e103034-lin> 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 --EzoGi9kFQAnUjl0a Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, May 28, 2014 at 01:10:01PM +0100, Morten Rasmussen wrote: > The basic problem is that worst case: sum starting from 0 and period > already at LOAD_AVG_MAX =3D 47742, it takes LOAD_AVG_MAX_N =3D 345 periods > (ms) for sum to reach 47742.=20 But it takes only 4 periods (4*32ms) to get ~94% of the way there,=20 So our half-time is 32 * 1024 ms, now look at \Sum_i=3D1,4 1/(2^i) =3D 0.9375. So 4 periods (4*32*1024=3D131072 ms) gets us ~94% of the way there. Now, granted, 4 periods of 32-ish ms is still very long, but nowhere near as horrid as the full convergence. --EzoGi9kFQAnUjl0a Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJThf4KAAoJEHZH4aRLwOS6920P/3Mo61XO0U0+Yp4uw5kGaWAp GVUQZY/Eio38+gIM8E8a6QNmBJET6QXMWwRvQTe2rZljRhnWeb+wzDzcyyFF2DzA fI8dJd8iD6x+ZGtVsIiDQcgdft6fSiiZdSEvYmSuH9SJL1NqRljYeJsg2X6X5ATT ZNRCnzlwN+ynyepJ8VUMzW265aUYlPB/iSuUqOqsVWInVAOxJv2bih7LyHRL/nvc BgFtKNHZKDGQoUbCvVKpIoube+EKrpY78ILK0spKFIzGLD/7Wm+uR30fupm/jvUT 3UL+DOhv6M1Qi7ftCaahbN9ew/CXZkCRZ2++z0/KdC3Zzo5mkVnH9Ue0ieNrmHTX +ajxJEanjLyf2+ixh+D94OfYsjwuRYkwGVXPbdWoZm392VJzem0M1C0G3yhynr3G r/av3Jaf0viXKBQJ1l2kTL+DOLRI2iuG9yyCfqYXjGKhEw2FuIYnSvsNksfQ7jnA WAyHx9+D/0xlwwVAeelsV7rVdOKtgvmj3vDaVV7jF/SeI6kjGhecKfVC4TTT5ZKb UgqCEukVmm74K6Wl3bdOo1K/wZqecQhiS9nU1sx/7/H7OsKHK8AtQorW1NbpBXgP gvHP1pIpR8yybm2Jx87n0I+evWAy0Zz+EjRKl1+ahvE1HfPRoxfYqOiH4p9SL1Cy 9JkYhNIbIyztfTszt1Ac =tD/y -----END PGP SIGNATURE----- --EzoGi9kFQAnUjl0a--