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From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
To: Ben Laurie <benl@freebsd.org>
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Date: Tue, 02 Oct 2012 19:22:40 +0200
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	=?utf-8?Q?rav=22's?= message of "Tue, 02 Oct 2012 15:07:03 +0200")
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Cc: Jonathan Anderson <jonathan.anderson@cl.cam.ac.uk>,
	Pawel Jakub Dawidek <pjd@freebsd.org>,
	John Baldwin <jhb@freebsd.org>, freebsd-security@freebsd.org,
	RW <rwmaillists@googlemail.com>,
	Mariusz Gromada <mariusz.gromada@gmail.com>
Subject: Re: Collecting entropy from device_attach() times.
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Dag-Erling Sm=C3=B8rgrav <des@des.no> writes:
> http://people.freebsd.org/~des/attachtimes-text.txz

1) There is a bug in the program - I made a couple of changes which I
   didn't like but didn't fully revert.  The (argc !=3D 0) in main()
   should actually be (argc =3D=3D 0).

2) I modified the program to create a histogram of the lower bits and
   looked at that in gnuplot.  It was immediately obvious that the
   distribution is extremely non-uniform.  I suspect that this is - at
   least in part - due to the weird way get_cyclecount() computes the
   value it returns.  We should either rewrite it to return something
   sensible or nuke it and use binuptime() instead.

I uploaded a new tarball with the improved program and the histogram:

  http://people.freebsd.org/~des/attachtimes-total.txz

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no