Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755321Ab0LAV1q (ORCPT ); Wed, 1 Dec 2010 16:27:46 -0500 Received: from mail-qw0-f46.google.com ([209.85.216.46]:43104 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752545Ab0LAV1p (ORCPT ); Wed, 1 Dec 2010 16:27:45 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=M4cimjANcLVrsFgWa3ekNO1xCT7ViyutCwi+NBAvIZVdOWhKtbKseHtZ/H3kA842fH YjsHVqKe9RUp0PPWgCEvEEl+AkT9k8rMwXroNo7hShpACGBg54V48ke/KALiqt7XD/MV oJlb+qlWU01qByfz1XuvF7k6e08AVGKqW+cB4= Date: Wed, 1 Dec 2010 16:27:38 -0500 From: tmhikaru@gmail.com To: Peter Zijlstra Cc: tmhikaru@gmail.com, Damien Wyart , Venkatesh Pallipadi , Chase Douglas , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, Kyle McMartin Subject: Re: High CPU load when machine is idle (related to PROBLEM: Unusually high load average when idle in 2.6.35, 2.6.35.1 and later) Message-ID: <20101201212738.GA16944@roll> References: <1289390424.2191.98.camel@laptop> <20101114051406.GA2050@roll> <20101125133106.GA12914@brouette> <1290693807.2145.36.camel@laptop> <1290888920.32004.1.camel@laptop> <20101128114027.GA2745@brouette> <1291030726.32004.4.camel@laptop> <20101129194041.GA8280@roll> <1291071677.32004.527.camel@laptop> <1291129145.32004.874.camel@laptop> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gKMricLos+KVdGMg" Content-Disposition: inline In-Reply-To: <1291129145.32004.874.camel@laptop> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2689 Lines: 68 --gKMricLos+KVdGMg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 30, 2010 at 03:59:05PM +0100, Peter Zijlstra wrote: > On Tue, 2010-11-30 at 00:01 +0100, Peter Zijlstra wrote: > >=20 > > Ok, that's good testing.. so its still not quite the same as NO_HZ=3Dn, > > how about this one? > >=20 > > (it seems to drop down to 0.00 if I wait a few minutes with top -d5) >=20 > OK, so here's a less crufty patch that gets the same result on my > machine, load drops down to 0.00 after a while. >=20 > It seems a bit slower to reach 0.00, but that could be because I > actually changed the load computation for NO_HZ=3Dn as well, I added a > rounding factor in calc_load(), we no longer truncate the division. >=20 > If people want to compare, simply remove the third line from > calc_load(): load +=3D 1UL << (FSHIFT - 1), to restore the old behaviour. For some bizzare reason, this version has a small but noticable amount of jitter and never really seems to hit 0.00 on my machine, tends to jump around at low values between 0.03 to 0.08 on a routine basis: 16:20:42 up 16:31, 4 users, load average: 0.00, 0.01, 0.05 the jitter seems to have no visible reason for it happening; with no networking, disk access or a process waking up and demanding attention from the cpu, it goes back up. Mind this is obviously NOT as horrible as it was originally, but I'd like to find out why it's acting so differently. I'm going to try this variant again with that line you were talking about disabled and see if it reacts differently. I get the feeling if it's the rounding factor - since you say that was changed for BOTH nohz=3Dy and n, t= hat it's not really a problem in the first place, and likely is very low load that wasn't being accurately reported before. Tim McGrath --gKMricLos+KVdGMg Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEVAwUBTPa9ypEncCrqzVruAQJ8Bgf/U6Bdx+PfSNpNJRpqUTdLpCAcztNksJUl 3Acaz3QqsSWp7njtJ5khQPslpQBXG1sMqr1z7AXub+6Xc/PFC5465bcNcMFkR0tn ZHmO8oYB7uUozGZ9GduEHb6P/V+t4+khQeug1LBtVQeR6CIBUeyr0flGx0ZiHX6M ggmHrnr13vaxyujKhqKO+IWrSHJDiXUQfK+HNHh9zoRD6uIbMlTCYLkDBghDJ1Lq 30g/EofLMTNzYATjO+2HFGBV3bsRUOBsom0TivjFAdL4QnRk8/QewuqQfkQIldFU cVqUhvqeCYKiOvd0EJoIwPWqTyF8G8M9K0NPrf/vBLTpDCjziTiw1g== =X/+o -----END PGP SIGNATURE----- --gKMricLos+KVdGMg-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/