netdev - Re: [PATCH v6] net: batch skb dequeueing from softnet input_pkt

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Date:	Mon, 3 May 2010 17:52:04 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, hadi@...erus.ca,
	xiaosuo@...il.com, therbert@...gle.com, shemminger@...tta.com,
	netdev@...r.kernel.org, lenb@...nel.org
Subject: Re: [PATCH v6] net: batch skb dequeueing from softnet
	input_pkt_queue

> so the hard problem is that on going idle, the local timers need to be
> funneled to the external HPET. Afaik right now we use one channel of
> the hpet, with the result that we have one global lock for this.
> 
> HPETs have more than one channel (2 or 3 historically, newer chipsets
> iirc have a few more), so in principle we can split this lock at least
> a little bit... if we can get to one hpet channel per level 3 cache
> domain we'd already make huge progress in terms of cost of the
> contention....

I suggested the same thing a few emails up @) (great minds think 
alike etc.etc. @) . 

I'm not sure how difficult it would be to implement though.

Potential issues:

Some user applications use the hpet channels directly through
the character device interface so there would be a potential
compatibility issue (but maybe that should be just moved
to be emulated with a hrtimer ?)

And if multiple broadcast controllers are elected this might
make it harder to become idle.

-Andi
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