netdev - Re: [RFC PATCH 2/2] tcp: Early SYN limit and SYN cookie handling to mitigate SYN floods

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Date:	Wed, 30 May 2012 10:24:48 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hans Schillstrom <hans.schillstrom@...csson.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Jesper Dangaard Brouer <jbrouer@...hat.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Christoph Paasch <christoph.paasch@...ouvain.be>,
	"David S. Miller" <davem@...emloft.net>,
	Martin Topholm <mph@...h.dk>, Florian Westphal <fw@...len.de>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [RFC PATCH 2/2] tcp: Early SYN limit and SYN cookie handling
 to mitigate SYN floods

On Wed, 2012-05-30 at 10:03 +0200, Hans Schillstrom wrote:

> We have this option running right now, and it gave slightly higher values.
> The upside is only one core is running at 100% load.
> 
> To be able to process more SYN an attempt was made to spread them with RPS to 
> 2 other cores gave 60% more SYN:s per sec
> i.e. syn filter in NIC sending all irq:s to one core gave ~ 52k syn. pkts/sec
> adding RPS and sending syn to two other core:s gave ~80k  syn. pkts/sec
> Adding more cores than two didn't help that much.

When you say 52.000 pkt/s, is that for fully established sockets, or
SYNFLOOD ?

19.23 us to handle _one_ SYN message seems pretty wrong to me, if there
is no contention on listener socket.



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