netdev - Re: [PATCH net-next 2/2] net: use reciprocal_divide instead of reimplementing it

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Message-ID: <1378216954.7360.25.camel@edumazet-glaptop>
Date:	Tue, 03 Sep 2013 07:02:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] net: use reciprocal_divide instead of
 reimplementing it

On Tue, 2013-09-03 at 12:26 +0200, Daniel Borkmann wrote:
> Replace these places with reciprocal_divide() inline function instead of
> reimplementing it each time, thus it will become easier to read. We do not
> need to explicitly include its header as it's pulled in from linux/net.h
> anyway.

Sure, (((u64) hash * qcount) >> 32) happens to be
reciprocal_divide(hash, qcount) but the result depends on hash being
well distributed in [0 .. ~0U] space.

So 'reciprocal' and 'divide' do not accurately describe this exact
operation.

I suggest making the thing more descriptive.

(And discussed on lkml btw)


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