netdev - Re: [PATCH RFC]: soreuseport: Bind multiple sockets to same port

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Date:	Mon, 19 Apr 2010 19:16:58 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH RFC]: soreuseport: Bind multiple sockets to same port

Le lundi 19 avril 2010 à 08:38 -0700, Tom Herbert a écrit :

> Calling it a nightmare be be a little strong.  It is true that this
> could create long chains that need to be walked, but this might be
> done with good cache locality of the structures.  In any case, the
> lock contention seems to overshadow the cost of this; we were able to
> increase max number of DNS queries/sec by about 60% (I will try to
> publish some numbers this week).
> 

I have no doubt this patch increases performances, but I think its not a
long term solution. We can do better ;)


> >
> I agree that CPU awareness is desirable, but I'm really hesitant to
> resort to pinning; this can become pretty tangled on a shared server
> running a bunch of different applications-- would be nice if the
> kernel can just figure out the right thing to do :-)
> 

OK I can understand this, but please use an array of sockets bound to
same tuple, so that lookup stay constant, regardless of number of
sockets. UDP fast path is a sensible area for financial applications.

Once anchor is found in normal udp hashtable, the choice of a random
target in its array is O(1) too (you could use skb->rxhash if not null)

Hmm, maybe we even could use same mechanism for multicast, since we
currently perform a very expensive loop.



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