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Date:	Tue, 20 Feb 2007 14:45:35 +0300
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	akepner@....com, linux@...izon.com, davem@...emloft.net,
	netdev@...r.kernel.org, bcrl@...ck.org
Subject: Re: Extensible hashing and RCU

On Tue, Feb 20, 2007 at 12:34:59PM +0100, Eric Dumazet (dada1@...mosbay.com) wrote:
> > Getting into account that network stack with NAPI schedules several
> > packets to be queued into socket and all that happens without any
> > infuence from userspace, trie/tree wins again in that regard that
> > majority of the tree will be in the cache already.
> 
> Nope, you receive 100 packets for 100 different flows. Only the code may be in 
> cache (minus for the first packet), and the very top of the tree...
> 
> Forget cache. Forget it.

First packet populates half of the top of the tree/trie to get to the
bottom - another one goes to completely different location, but it still
need to go through some of the just populated entries - it is a
tree/trie nature - probability of a hit decreases two times in each
level (for binary tree, for trie is is very different) until first 'miss', 
but it is still non zero.

But generally I afgree that talking about caches can only be valid when
all other issues are resolved completely. So, we need a patch.

-- 
	Evgeniy Polyakov
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