netdev - Re: [PATCH 3/4] llc: use a device based hash table to speed up multicast delivery

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Message-ID: <4B184F4C.3060407@gmail.com>
Date:	Fri, 04 Dec 2009 00:52:44 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Octavian Purdila <opurdila@...acom.com>
CC:	netdev@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH 3/4] llc: use a device based hash table to speed up multicast
 delivery

Octavian Purdila a écrit :
> 
> Yes, that is probably not appropriate for upstream. What would be a good 
> value?
> 

A small one to begin (say 64).

> Since at this point we are using UP ports contention is not really an issue 
> for us. I've extrapolated this (lock per hash bucket) based on how locking is 
> done in other places, like UDP. 

Yes but you know we want to remove those locks per UDP hash bucket, since we dont
really need them anymore. ;)


If you remember, we had in the past one rwlock for the whole UDP table.

Then this was converted to one spinlock per hash slot (128 slots) + RCU lookups for unicast RX

Then we dynamically sized udp table at boot (up to 65536 slots)

multicast optimization (holding lock for small duration + double hashing)

bind optimization (thanks to double hashing)

To be done :

1) multicast RX can be done without taking any lock, and RCU lookups
2) zap all locks and use one lock, or a small array of hashed spinlocks


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