linux-kernel - Re: [PATCH 1/2] hw_random: core updates to allow more efficient drivers

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Message-ID: <4B139E3D.1020905@collabora.co.uk>
Date:	Mon, 30 Nov 2009 10:28:13 +0000
From:	Ian Molton <ian.molton@...labora.co.uk>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] hw_random: core updates to allow more efficient drivers

Rusty Russell wrote:

> And might as well just #defube RNG_BUFFSIZE SMP_CACHE_BYTES (or use
> SMP_CACHE_BYTES here and sizeof() elsewhere).

This can lead to a rather small (4 byte) buffer on some systems, however
I don't know if in practice a tiny buffer or a big one would be better
for performance on those machines. I guess if its a problem someone can
patch the code to allocate a minimum of (say) 16 bytes in future...

so changed :)

>>> +		if (!data_avail) {
>>> +			bytes_read = rng_get_data(current_rng, rng_buffer,
>>> +				RNG_BUFFSIZE, !(filp->f_flags & O_NONBLOCK));
>> No need to pass rng_buffer to the helper as there's only one with global
>> scope.
> 
> Naah, I like the separation; it matches the rest of the kernel and means we
> can get funky with buffer management in 10 years time when we rewrite this
> again.

Tweaked to use sizeof().
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