netdev - Re: [PATCH 1/4]: net: Allow RX queue selection to seed TX queue hashing.

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Date:	Wed, 28 Jan 2009 12:22:31 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 1/4]: net: Allow RX queue selection to seed TX queue
 hashing.

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Wed, 28 Jan 2009 19:53:58 +1100

> So can you think of a scenario where we really need this added
> protection?

No matter what you think about the randomness aspect, our
divide avoidance technique being used here will still
get in the way of the situations you seem to be concerned
about.

We do the jhash et al. magic in order to be able to use a
multiply to get the modulus.  So the function computing from
RX to TX queue numbers will never be straightforward.

And since we do need to do the jhash to make that multiply
trick work, the randomness comes essentially for free and
does not make the RX to TX queue relationship any more or
less straightforward.
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