From: Chris Metcalf <cmetcalf@mellanox.com>
To: Peter Zijlstra <peterz@infradead.org>, Wanpeng Li <kernellwp@gmail.com>
Cc: Rik van Riel <riel@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Christoph Lameter <cl@linux.com>, Ingo Molnar <mingo@kernel.org>,
Luiz Capitulino <lcapitulino@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Viresh Kumar <viresh.kumar@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] nohz_full: Make sched_should_stop_tick() more conservative
Date: Mon, 25 Apr 2016 17:30:23 -0400 [thread overview]
Message-ID: <571E8C6F.8010701@mellanox.com> (raw)
In-Reply-To: <20160421160315.GK24771@twins.programming.kicks-ass.net>
On 4/21/2016 12:03 PM, Peter Zijlstra wrote:
> On Thu, Apr 21, 2016 at 04:42:13PM +0200, Peter Zijlstra wrote:
>
>> So I think that is indeed the right thing here. But looking at this
>> function I think there's more problems with it.
>>
>> It seems to assume that if there's FIFO tasks, those will run. This is
>> incorrect. The FIFO task can have a lower prio than an RR task, in which
>> case the RR task will run.
>>
>> So the whole fifo_nr_running test seems misplaced, it should go after
>> the rr_nr_running tests. That is, only if !rr_nr_running, can we use
>> fifo_nr_running like this.
> A little something like so perhaps; can anybody test?
Tested-by: Chris Metcalf <cmetcalf@mellanox.com>
To be clear, I only tested that it fixed my original bug, where we weren't
kicking a remote cpu when we should have been; I have not tested that
it works properly in the presence of RR or FIFO scheduled tasks.
But this or something like it should definitely go into 4.6 before it's done.
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
next prev parent reply other threads:[~2016-04-25 21:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 19:42 [PATCH] nohz_full: Make sched_should_stop_tick() more conservative Chris Metcalf
2016-04-04 19:12 ` Rik van Riel
2016-04-04 19:23 ` Peter Zijlstra
2016-04-18 2:00 ` Wanpeng Li
2016-04-21 14:42 ` Peter Zijlstra
2016-04-21 16:03 ` Peter Zijlstra
2016-04-25 21:30 ` Chris Metcalf [this message]
2016-04-28 10:24 ` [tip:sched/urgent] nohz/full, sched/rt: Fix missed tick-reenabling bug in sched_can_stop_tick() tip-bot for Peter Zijlstra
2016-04-28 13:30 ` Frederic Weisbecker
2016-04-04 19:31 ` [PATCH] nohz_full: Make sched_should_stop_tick() more conservative Chris Metcalf
2016-04-04 19:36 ` Rik van Riel
2016-04-05 0:27 ` Chris Metcalf
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