netdev - Re: [PATCH net-next-2.6] ipv4: more compliant RFC 3168 support

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Date:	Mon, 16 May 2011 23:38:38 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hagen Paul Pfeifer <hagen@...u.net>
Cc:	Stefanos Harhalakis <v13@....gr>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next-2.6] ipv4: more compliant RFC 3168 support

Le lundi 16 mai 2011 à 23:33 +0200, Hagen Paul Pfeifer a écrit :
> * Eric Dumazet | 2011-05-15 18:01:50 [+0200]:
> 
> >Problem of this version is that common frames in the Internet (NOT_ECT
> >or ECT_X or ECT_X) will take the longest path to come to "return 0;"
> >
> >a switch() version is fast because gcc emits a table based jump
> 
> Sure? Is the table access not an dCache miss? E.g.
> 
> 4003dc: ff 24 fd 58 06 40 00  jmpq   *0x400658(,%rdi,8)
> 
> Not sure if jump table access is superior these days ...
> 

Check v2 of patch, it is fine, small, fast ;)

By the way, you dont want to know how many cpu cycles we spend in IP
defrag functions... Really its insane.



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