From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757453Ab1FPQwH (ORCPT ); Thu, 16 Jun 2011 12:52:07 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:45573 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753831Ab1FPQwE (ORCPT ); Thu, 16 Jun 2011 12:52:04 -0400 X-Authority-Analysis: v=1.1 cv=5asQ6euaRPJxDdFxwvXsn6JDb7fmFbz8qWDLMfa45gU= c=1 sm=0 a=LNPuZ-ntsc0A:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=pGLkceISAAAA:8 a=r-BWzVmcDX1c6V8RMDMA:9 a=0LQOZpJ_b5C0SublwokA:7 a=PUjeQqilurYA:10 a=MSl-tDqOz04A:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Subject: Re: [PATCH] sched: find all lowest run-queues for RT task From: Steven Rostedt To: Hillf Danton Cc: LKML , Mike Galbraith , Yong Zhang , Peter Zijlstra , Ingo Molnar In-Reply-To: References: Content-Type: text/plain; charset="ISO-8859-15" Date: Thu, 16 Jun 2011 12:52:02 -0400 Message-ID: <1308243122.9218.143.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-06-03 at 22:11 +0800, Hillf Danton wrote: > When finding the lowest run-queue for a given RT task, as seen in cases such as > select_task_rq_rt() and find_lock_lowest_rq(), RQs with no RT tasks are also > eligible for both RR and FIFO RT tasks. > > Minor change is added, when initializing cpupri, to record non-RT RQs which are > upated automatically, due to the cool design and implementation of cpupri, when > RT RQs are set and unset. Then they could be included in the selected CPUs by > cpupri_find(). > > A call for cpupri_set() is also added when a RQ has no RT task to run. I just analyzed the code, and only the first part of the patch seems OK. > Signed-off-by: Hillf Danton > --- > kernel/sched_cpupri.c | 4 +++- > kernel/sched_rt.c | 4 ++++ > 2 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched_cpupri.c b/kernel/sched_cpupri.c > index 2722dc1..d4c0b46 100644 > --- a/kernel/sched_cpupri.c > +++ b/kernel/sched_cpupri.c > @@ -181,8 +181,10 @@ int cpupri_init(struct cpupri *cp) > goto cleanup; > } > > - for_each_possible_cpu(i) > + for_each_possible_cpu(i) { > cp->cpu_to_pri[i] = CPUPRI_INVALID; > + cpupri_set(cp, i, MAX_RT_PRIO); > + } This is OK, and I may add it. It's just an initialization, and because things like the migration thread run on all CPUs, the first time an RT task is run on a CPU and dequeued, it will have the cpupri_set() to MX_RT_PRIO anyway. But for clean up sake, it may be good to initialize it to a valid mask and not be ZERO. > return 0; > > cleanup: > diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c > index 88725c9..4dd6e45 100644 > --- a/kernel/sched_rt.c > +++ b/kernel/sched_rt.c > @@ -1158,6 +1158,10 @@ static struct task_struct > *pick_next_task_rt(struct rq *rq) > * lock again later if there is no need to push > */ > rq->post_schedule = has_pushable_tasks(rq); > + > + /* this CPU is no longer RT if no task picked to feed it */ > + if (! p) > + cpupri_set(&rq->rd->cpupri, rq->cpu, MAX_RT_PRIO); Now this is where things are not needed, because when we dequeue the last RT task, this is already done by the dequeue code. -- Steve > #endif > > return p;