Re: [RFC] frandom - fast random generator module

[Andreas Dilger]

On Oct 16, 2003  14:08 -0500, Matt Mackall wrote:
> On Thu, Oct 16, 2003 at 12:38:28PM -0600, Andreas Dilger wrote:
> > It was a 2-way SMP system.  We use the RNG a fair amount (enough to know
> > that 2 CPUs can race and return the same value from get_random_bytes() ;-)
> 
> Sure this is a race and not a birthday paradox? How recent is this?
> Possibly before locking was added to random.c?

This is with a 2.4 kernel, which AFAIK doesn't have any locking.

> > so we had to put a spinlock around our calls to that.  Even so, oprofile
> > showed extract_entropy() and SHATransform() near the top of CPU users.
> 
> Ok, the lock contention would be with add_entropy_words. I've got code
> that reduces calls to SHATransform for /dev/urandom, but it require
> addressing the starvation issues between /dev/random and /dev/urandom first.

But there isn't an in-kernel interface to "/dev/urandom" so that doesn't
help us.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/

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