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

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Date:	Mon, 03 May 2010 07:17:14 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	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

Le dimanche 02 mai 2010 à 20:50 -0700, Arjan van de Ven a écrit :

> we effectively do that. The thing is that C2 is so low cost normally
> that it's still worth it even at 20k wakeups...
> 
> this is where the bios tells us how "heavy" the states are....
> and 64 usec... is just not very much.

Maybe its low cost, (apparently, it is, since I can reach ~900.000 ipis
on my 16 cores machine) but multiply this by 16 or 32 or 64 cpus, and
clockevents_notify() cost appears to be a killer, all cpus compete on a
single lock.

Maybe this notifier could use RCU ?


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