From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Josh Cartwright <joshc@ni.com>
Cc: Daniel Wagner <wagi@monom.org>,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Daniel Wagner <daniel.wagner@bmw-carit.de>
Subject: Re: [RFC v0] Use swait in completion
Date: Wed, 9 Mar 2016 13:24:23 +0100 [thread overview]
Message-ID: <20160309122423.GD10517@linutronix.de> (raw)
In-Reply-To: <20160308182656.GA27081@jcartwri.amer.corp.natinst.com>
* Josh Cartwright | 2016-03-08 12:26:56 [-0600]:
>Is it really just about latency? Does this deferral not lead to an
>inversion in the case where the single woken task isn't the highest
>priority waiter on the completion (and doesn't run due to a
>middle-priority thing spinning)?
This would be case, yes. Not only with deferral. Say you have two
waters: 1st one is MID-prio and the second is HI-prio. Currently after
the wakeup of the MID-prio waiter you get preempted. Waking all of them
at once would put the second waiter first on the CPU.
Samething without the deferral flag.
>In order for this to work, it seems like the chosen waiter would need to
>inherit the highest priority of all waiters (which AFAICT isn't
>happening).
sorting the waiters by priority? This will be fun. This is only done for
the rtmutex waiters.
> Josh
Sebastian
next prev parent reply other threads:[~2016-03-09 12:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 15:59 [RFC v0] Use swait in completion Daniel Wagner
2016-03-08 15:59 ` [RFC v0] sched/completion: convert completions to use simple wait queues Daniel Wagner
2016-03-08 17:52 ` [RFC v0] Use swait in completion Sebastian Andrzej Siewior
2016-03-08 18:07 ` Daniel Wagner
2016-03-08 18:26 ` Josh Cartwright
2016-03-09 12:24 ` Sebastian Andrzej Siewior [this message]
2016-03-28 18:57 ` Steven Rostedt
2016-03-31 6:14 ` Daniel Wagner
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