linux-kernel - Re: [GIT PULL tip/genirq] Please pull from lost-spurious-irq

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Date:	Tue, 3 Aug 2010 13:43:46 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Tejun Heo <teheo@...e.de>
cc:	lkml <linux-kernel@...r.kernel.org>, Jeff Garzik <jeff@...zik.org>,
	Greg KH <gregkh@...e.de>
Subject: Re: [GIT PULL tip/genirq] Please pull from lost-spurious-irq

Tejun,

On Tue, 3 Aug 2010, Tejun Heo wrote:
> I agree that timer multiplexing is a rather ugly thing and it would be
> great to remove it.  You're right that it doesn't make whole lot of
> difference whether the timer is global or local if it's low frequency
> and in fast paths expect/unexpect would be able to just test its list
> entry and set/clear currently expecting status without messing with
> the global timer or lock.  Then, we can have a single low freq timer
> for expect/unexpect and the other for actual polling.

And the third one for watch, right ? That would give us separate timer
functions which each serve a particular purpose.

When you go for it, can you please simplify all the heuristics? 

spurious poll: 

 One fixed poll interval is enough. The retry logic can be made
 simple, just set it back to interrupt delivery once per minute and
 limit the storm to 10.

watch:

 Get rid of the interrupt context work and do all the work in the
 timer. Use a fixed interval and either keep it forever or remove it.

expect:

 Use a slow fixed interval and just do the expect/unexpect fast
 marking. A nice thing would be to have a counter of expect calls so
 we can switch off the timer when there is no activity within 10
 seconds.

> How does that sound to you?

Way better. :)

Thanks,

	tglx
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