From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756399AbaEIJMw (ORCPT ); Fri, 9 May 2014 05:12:52 -0400 Received: from casper.infradead.org ([85.118.1.10]:48135 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756373AbaEIJMs (ORCPT ); Fri, 9 May 2014 05:12:48 -0400 Date: Fri, 9 May 2014 11:12:45 +0200 From: Peter Zijlstra To: minyard@acm.org Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Corey Minyard Subject: Re: [PATCH] sched: Initialize rq->age_stamp on processor start Message-ID: <20140509091245.GN30445@twins.programming.kicks-ass.net> References: <20140508161337.GF30445@twins.programming.kicks-ass.net> <1399574859-11714-1-git-send-email-minyard@acm.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="FexDM9E/OpjgUmaq" Content-Disposition: inline In-Reply-To: <1399574859-11714-1-git-send-email-minyard@acm.org> 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 --FexDM9E/OpjgUmaq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, May 08, 2014 at 01:47:39PM -0500, minyard@acm.org wrote: > From: Corey Minyard >=20 > If the sched_clock time starts at a large value, the kernel will spin > in sched_avg_update for a long time while rq->age_stamp catches up > with rq->clock. >=20 > The comment in kernel/sched/clock.c says that there is no strict promise > that it starts at zero. So initialize rq->age_stamp when a cpu starts up > to avoid this. >=20 > I was seeing long delays on a simulator that didn't start the clock at > zero. This might also be an issue on reboots on processors that don't > re-initialize the timer to zero on reset, and when using kexec. >=20 > Signed-off-by: Corey Minyard Thanks --FexDM9E/OpjgUmaq Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTbJwNAAoJEHZH4aRLwOS642QP/RSRwLinBj7c6bxXYpZvQtO/ d9DvVxxjSXYFq7C3Dq80B09BrXUbWL4RKJxdK42YVqdBVfwSWYGw9spiRZ7+u777 7YR8SU8RAU2t//F32lT+DUlHMM4iYCpP5AgxI5j4TJIn4/o7eZ1McHc/4LTAHIQp 4wCwbvBclqmJNOpC3hzNfg+3CKYYPcnZiob/9my/oM9D10dVV88PGL557tayvB3A 887j73KncplvNRV6wdMM0p+lCwKEWYDMHD+PDDYOk98M/ybTAPnNEQkoxXZGk7Ny xVRO3alHbGEHkuSI65A6RAOmyHFHM8D5hJSD9xBXRWMpFcQc01aCOENfNAnbsI70 cSDcVu+d3wF5zQiZ5kHeuSafh4rCW6xJzRUhB9/Z4mSy2Ndeoa56A9g/ekzCXCWh 7+5De1LNtHP9krvGYmm/L6q3vqUmkbliEW7LlVKR/E85eA0wMcsi++rU4+GtlIWJ muJZbwBJ8pNEGkcoo5l/1HlGjtXwjRvLu/TfgZFD6KhqelgWUFuWwHxN+YfrK4c4 dlDaZ9fQtO6KIHbA14pNq1j4LpC+vVyWedUEeZJYP4pBZQ2PImwszv0/l2X/jl7+ 1a5tergvbAOeCC24L00jngTKrC2mT32i813650c49bbPUHIXj8gLtia2jRXMIElM d6GeUx+M7iq1MVrNoaMX =6E+m -----END PGP SIGNATURE----- --FexDM9E/OpjgUmaq--