Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752818AbbH0QuF (ORCPT ); Thu, 27 Aug 2015 12:50:05 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:34325 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751635AbbH0QuD (ORCPT ); Thu, 27 Aug 2015 12:50:03 -0400 Message-ID: <1440694201.32300.72.camel@j-VirtualBox> Subject: Re: [PATCH v2] sched: fix nohz.next_balance update From: Jason Low To: Vincent Guittot Cc: Peter Zijlstra , Ingo Molnar , linux-kernel , Preeti U Murthy , Linaro Kernel Mailman List , jason.low2@hp.com Date: Thu, 27 Aug 2015 09:50:01 -0700 In-Reply-To: References: <1438595750-20455-1-git-send-email-vincent.guittot@linaro.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1430 Lines: 29 On Thu, 2015-08-27 at 13:21 +0200, Vincent Guittot wrote: > Hi, > > On 3 August 2015 at 11:55, Vincent Guittot wrote: > > Since commit d4573c3e1c99 ("sched: Improve load balancing in the presence > > of idle CPUs"), the ILB CPU starts with the idle load balancing of other > > idle CPUs and finishes with itself in order to speed up the spread of tasks > > in all idle CPUs. > > > > The this_rq->next_balance is still used in nohz_idle_balance as an > > intermediate step to gather the shortest next balance before updating > > nohz.next_balance. But the former has not been updated yet and is likely to > > be set with the current jiffies. As a result, the nohz.next_balance will be > > set with current jiffies instead of the real next balance date. This > > generates spurious kicks of nohz ilde balance. > > > > nohz_idle_balance must set the nohz.next_balance without taking into > > account this_rq->next_balance which is not updated yet. Then, this_rq will > > update nohz.next_update with its next_balance once updated and if necessary. > > > > Signed-off-by: Vincent Guittot Acked-by: Jason Low -- 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/