netdev - Re: [PATCH next-next-2.6] netdev: better dev_name

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Message-ID: <4AE64F72.6060802@gmail.com>
Date:	Tue, 27 Oct 2009 02:40:02 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
CC:	opurdila@...acom.com, krkumar2@...ibm.com, hagen@...u.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH next-next-2.6] netdev: better dev_name_hash

David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Mon, 26 Oct 2009 15:55:10 +0100
> 
>> But should we really care ?
> 
> The only thing I see consistently in this thread is that
> jhash performs consistently well and without any tweaking.
> 
> And without any assumptions about the characteristics of
> the device names.  I've seen everything from the traditional
> "eth%d" to things like "davem_is_a_prick%d" so you really cannot
> optimize for anything in particular.
> 
> Jenkins is ~50 cycles per round of 4 bytes last time I checked, give
> or take, and that was on crappy sparc. :-) So the execution cost is
> really not that bad, contrary to what I've seen claimed as an argument
> against using jhash here.
> 
> And if I-cache footprint is really an issue, we can have one
> out-of-line expansion of jhash somewhere under lib/ since we use jhash
> in so many places these days.

Well, since Stephen posted a generic patch on lkml, I suspect we'll take
the dcache hash anyway ?

But yes, last time I checked, jhash was pretty big, so an out-of-line
version is welcome :)
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