Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753346Ab1BWEVA (ORCPT ); Tue, 22 Feb 2011 23:21:00 -0500 Received: from mailout-de.gmx.net ([213.165.64.22]:36766 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752215Ab1BWEU7 (ORCPT ); Tue, 22 Feb 2011 23:20:59 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX19RBL8O3KdRqN3gcT8L3R2LfL2OVmrlAjf0D5V7qg 2tXugsnS+dtIe2 Subject: Re: [PATCH 1/2] sched: allow SCHED_BATCH to preempt SCHED_IDLE tasks From: Mike Galbraith To: Darren Hart Cc: Linux Kernel Mailing List , Peter Zijlstra , Ingo Molnar , richard.purdie@linuxfoundation.org In-Reply-To: <1298408674-3130-2-git-send-email-dvhart@linux.intel.com> References: <1298408674-3130-1-git-send-email-dvhart@linux.intel.com> <1298408674-3130-2-git-send-email-dvhart@linux.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 23 Feb 2011 05:20:54 +0100 Message-ID: <1298434854.7856.24.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.30.1.2 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1635 Lines: 46 On Tue, 2011-02-22 at 13:04 -0800, Darren Hart wrote: > Perform the test for SCHED_IDLE before testing for SCHED_BATCH (and ensure idle > tasks don't preempt idle tasks) so the non-interactive, but still important, > SCHED_BATCH tasks will run in favor of the very low priority SCHED_IDLE tasks. Yeah, that could be construed as a fairness fix for light SCHED_BATCH vs a heavy SCHED_IDLE. It should lower latencies for both when mixed. Acked-by: Mike Galbraith Nit below. > Signed-off-by: Darren Hart > CC: Peter Zijlstra > CC: Ingo Molnar > CC: Richard Purdie > --- > kernel/sched_fair.c | 12 +++++++----- > 1 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 0c26e2d..ff04bbd 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1857,16 +1857,18 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ > if (test_tsk_need_resched(curr)) > return; > > + /* Idle tasks are by definition preempted by non-idle tasks. */ > + if (unlikely(curr->policy == SCHED_IDLE) && > + likely(p->policy != SCHED_IDLE)) > + goto preempt; > + if (unlikely(curr->policy == SCHED_IDLE && p->policy != curr->policy)) goto preempt; Looks better to me. -Mike -- 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/