netdev - Re: [PATCH 3/3] chelsio: more receive cleanup

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Message-ID: <20061215172800.52713c89@freekitty>
Date:	Fri, 15 Dec 2006 17:28:00 -0800
From:	Stephen Hemminger <shemminger@...l.org>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	Jeff Garzik <jgarzik@...ox.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 3/3] chelsio: more receive cleanup

On Sat, 16 Dec 2006 01:26:04 +0100
Francois Romieu <romieu@...zoreil.com> wrote:

> Stephen Hemminger <shemminger@...l.org> :
> > Francois Romieu <romieu@...zoreil.com> wrote:
> [...]
> > Why, you can't predict copybreak on off
> 
> Plain gut feeling. I'd rather spend extra cycles on small packets (whose
> allocation is already optimized) and keep the normal packets less expensive
> on a 10Gb/s network card.
>

Likely/unlikely is an optimization that doesn't make a big difference and
I would rather the compiler choose unless it is something obvious like
an error path or external interrupt (like PHY).

There was some discussion on LKML, which I mostly forgot, that hinted that
on some architectures using likely/unlikely incorrectly could have a major
hit.


-- 
Stephen Hemminger <shemminger@...l.org>
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