netdev - Re: [PATCH net-next 1/2] net: introduce generic net_random

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Date:	Tue, 03 Sep 2013 05:41:57 -0700
From:	Joe Perches <joe@...ches.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH net-next 1/2] net: introduce generic net_random_N helper

On Tue, 2013-09-03 at 14:26 +0200, Daniel Borkmann wrote:
> On 09/03/2013 02:15 PM, Joe Perches wrote:
> > I think #define net_random() prandom_u32()
> > should be removed eventually as well.
> 
> Why? Assume there could be different PRNGs in future that have different properties
> (e.g. speed vs. period, etc). Then, changing net_random() to something else is way
> easier and less error-prone than searching through the whole subtree of net and
> replacing every occurrence of prandom_u32().

Maybe.  There are already instances of prandom_u32
in the net tree.  I don't find value in the indirection.

Akinobu Mita once posted a s/net_random/prandom_u32/
patch: https://lkml.org/lkml/2012/12/23/140

> > If gcc doesn't already do this optimization,
> > perhaps there are also some use of
> > 	net_random() % non_const
> > that could be optimized a bit using this API.
> 
> I agree with you, needs to be evaluated on a case by case basis for future work.

__builtin_constant_p is useful.


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