lkml.org 
[lkml]   [1999]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: arca-vm-26
I wrote:
> I don't think the source has to be _that_ good, so a linear feedback
> shift register should do. You can periodically mix in entropy from the
> random device into the LFSR value to keep it "fairly" random. (Say,
> whenever entropy enters the randomness pool),

I've changed my mind. For a VMA skiplist, I would try a polynomial
congruential generator similar to the kind used by BSD random(), as that
can also be extremely fast, and is pretty good.

Benjamin Saller Bender wrote:
> Can you imagine the VM or the network layer blocking to wait for
> the entorpy pool to refill though. The better the random() the better the
> spread on the tree, it becomes more important as N grows.

The LFSR suggestion doesn't involve any blocking. An LFSR, which is
very fast, provides random bits though they are not particularly good.
A skip list only needs bits, which suits an LFSR. New entropy is used
to stir the LFSR value to keep it fair -- to avoid identifiable long
term patterms. That is only done when new entropy arrives, not when a
random bit is required.

-- Jamie

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:49    [W:0.253 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site