From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756501AbaEPIEj (ORCPT ); Fri, 16 May 2014 04:04:39 -0400 Received: from casper.infradead.org ([85.118.1.10]:37108 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756226AbaEPIEa (ORCPT ); Fri, 16 May 2014 04:04:30 -0400 Date: Fri, 16 May 2014 10:04:24 +0200 From: Peter Zijlstra To: Ben Segall Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched: fix exec_start/task_hot on migrated tasks Message-ID: <20140516080424.GM11096@twins.programming.kicks-ass.net> References: <20140515225920.7179.13924.stgit@sword-of-the-dawn.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="w5nY8nmEklXMR7Cj" Content-Disposition: inline In-Reply-To: <20140515225920.7179.13924.stgit@sword-of-the-dawn.mtv.corp.google.com> 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 --w5nY8nmEklXMR7Cj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, May 15, 2014 at 03:59:20PM -0700, Ben Segall wrote: > task_hot checks exec_start on any runnable task, but if it has been > migrated since the it last ran, then exec_start is a clock_task from > another cpu. If the old cpu's clock_task was sufficiently far ahead of > this cpu's then the task will not be considered for another migration > until it has run. Instead reset exec_start whenever a task is migrated, > since it is presumably no longer hot anyway. >=20 > Signed-off-by: Ben Segall > --- > kernel/sched/fair.c | 3 +++ > 1 file changed, 3 insertions(+) >=20 > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 28ccf50..9f8dfeb 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4544,6 +4544,9 @@ migrate_task_rq_fair(struct task_struct *p, int nex= t_cpu) > atomic_long_add(se->avg.load_avg_contrib, > &cfs_rq->removed_load); > } > + > + /* We have migrated, no longer consider this task hot */ > + se.exec_start =3D 0; > } 0 isn't strictly the right thing to do here, since the clock can wrap, but being wrong every ~585 years isn't too big an issue for this. Thanks! --w5nY8nmEklXMR7Cj Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTdcaIAAoJEHZH4aRLwOS6Qt8P/2N6ObfDOgw0rcsARKeID+kM YDFX5W4ymgj33lvFF7cgNnfDPFgwt/IH7t0qMkYjywYmUfr9pizF5cC6p5IcnNZ+ 85xvtntzv0Ck9KtpOCIU2y7lHugYc8x/qbEe2gWNIHNoJ30OMLRihL6AaEkhu/wM P/iDk1YmQ9YYk/3chIuEqCLWjpFCI/2W82PdwBmB8PUDs2frSAjFGCN41yCIlW1s qaJcSnya5RXR1M3DsTawtaVlXOIJg+1Dof3RnO6/o7iw6ZmeWEvLrsQLArCx2gI+ aOszgtf7nHYRuKSkNQiSE7LEWQB4bhtix7YHEs8fDHeYx/Dg46bHxKu0gAOJyCtP fjYQjLCGbhJ1O/qyftaaMHwPFBjEyS6D6CwqWtBDbYaP17SP9X4bCrxxqVo63CwI 8ku0aejv1s7BOM/lm9qyFwpr4g8mdw6D8DJMliAZY2o7bwXa83tjfeo0/y9TWjf5 At3uuoIKocNurr/pYK38oi1FZCFCRSw9aMFhTo6T27hkIu9um54cOELcOlSlygGp RaZfNiZGW7w49SZJtLGYht6c/P3r+FJvDHq5/BZZWDx6wS8YePWL7fRhpOGyvvk5 V2unC7dsNFQRIJlkvEBN6F9WblItLZbhd4xIvCrp672Gg0C6nolCwf+4cKhlFXCX Nx+pufgKyMfNU0TZ7esy =iSl6 -----END PGP SIGNATURE----- --w5nY8nmEklXMR7Cj--