linux-kernel - Re: [RFC v0] Use swait in completion

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Date:	Tue, 8 Mar 2016 19:07:16 +0100
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Daniel Wagner <wagi@...om.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-rt-users@...r.kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC v0] Use swait in completion

On 03/08/2016 06:52 PM, Sebastian Andrzej Siewior wrote:
> However I don't think if your DEFER flag solution is all that bad. I
> have also the block-mq in -RT using swait and they perform wakes with
> irqs-off. Not in -RT but mainline. So me might need something to make it
> work properly. But if we defer the wakeup they might come at us and
> complain about the latency…

I intended to extend the test code to measure the latency diff as well.
Just to get a feeling how bad it is. At least with a lot of waiters on
the completion the current measurement indicate an improvement. I guess
with real workload the things look quite different.

cheers,
daniel