From: "Theodore Ts'o" <tytso@mit.edu>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Stephan Mueller <smueller@chronox.de>,
LKML <linux-kernel@vger.kernel.org>,
dave.taht@bufferbloat.net
Subject: Re: [PATCH] /dev/random: Insufficient of entropy on many architectures
Date: Tue, 10 Sep 2013 17:14:54 -0400 [thread overview]
Message-ID: <20130910211454.GJ29237@thunk.org> (raw)
In-Reply-To: <CAMuHMdXcXGpgE5ArcjNU-RgAr52qB8ih_b48jwR=+OqK4RDhFA@mail.gmail.com>
On Tue, Sep 10, 2013 at 10:48:00PM +0200, Geert Uytterhoeven wrote:
>
> So the first importance for random_get_fast_cycles() is that it needs to
> be fast. What's most important next: number of bits or high-frequency?
High-frequency. For example MIPS has a register which is bumped at
every clock tick, modulo the number of lines in the TLB. That's what
we're probably going to end up using for MIPS, on the assumption that
the time between interrupts is not likely going to be related to the
number of lines in the TLB. :-)
Something like jiffies has lots of bits, but since it's updated at a
much slower rate, it's not as useful if we are trying to measure
uncertainity based on the interrupt time. (Worse yet, depending on
how the architecture handles the clock, there mgiht be a very high
correlation between when the jiffies counter gets incremented and the
timer interrupt....)
And yes, we will need to make sure this gets well documented in the
sources when we introduce random_get_fast_cycles()....
Cheers,
- Ted
next prev parent reply other threads:[~2013-09-10 21:15 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 11:31 [PATCH] /dev/random: Insufficient of entropy on many architectures Stephan Mueller
2013-09-10 11:46 ` Geert Uytterhoeven
2013-09-10 15:04 ` Theodore Ts'o
2013-09-10 16:54 ` Stephan Mueller
2013-09-10 18:25 ` Theodore Ts'o
2013-09-10 19:15 ` Stephan Mueller
2013-10-10 6:50 ` Pavel Machek
2013-10-14 21:13 ` Theodore Ts'o
2013-09-10 20:48 ` Geert Uytterhoeven
2013-09-10 21:14 ` Theodore Ts'o [this message]
2013-09-11 6:49 ` Stephan Mueller
2013-09-12 11:59 ` Geert Uytterhoeven
2013-09-12 12:08 ` Stephan Mueller
2013-09-12 12:15 ` Geert Uytterhoeven
2013-09-12 12:35 ` Stephan Mueller
2013-09-12 12:47 ` Geert Uytterhoeven
2013-09-12 12:57 ` Stephan Mueller
2013-09-12 21:18 ` Jörn Engel
2013-09-13 11:33 ` Thorsten Glaser
2013-09-12 14:25 ` Theodore Ts'o
2013-09-10 19:38 ` John Stultz
2013-09-10 19:44 ` John Stultz
2013-09-10 19:47 ` Stephan Mueller
2013-09-10 20:35 ` John Stultz
2013-09-10 20:38 ` Theodore Ts'o
2013-09-10 20:46 ` John Stultz
2013-09-10 21:10 ` Theodore Ts'o
2013-09-10 22:08 ` John Stultz
2013-09-10 22:33 ` Theodore Ts'o
2013-09-11 0:31 ` John Stultz
2013-09-11 0:50 ` Theodore Ts'o
2013-09-11 1:14 ` John Stultz
2013-09-12 20:46 ` H. Peter Anvin
2013-09-12 21:07 ` Jörn Engel
2013-09-12 23:31 ` Theodore Ts'o
2013-09-12 23:35 ` Jörn Engel
2013-09-13 0:00 ` Jörn Engel
2013-09-16 15:40 ` [PATCH,RFC] random: make fast_mix() honor its name Jörn Engel
2013-09-21 21:25 ` Theodore Ts'o
2013-09-21 21:41 ` Theodore Ts'o
2013-09-22 3:05 ` Theodore Ts'o
2013-09-22 21:01 ` Jörg-Volker Peetz
2013-09-22 21:27 ` Theodore Ts'o
2013-09-22 20:53 ` Jörn Engel
2013-09-22 23:36 ` Theodore Ts'o
2013-09-23 0:16 ` Jörn Engel
2013-09-23 2:43 ` Theodore Ts'o
2013-09-23 15:02 ` Jörn Engel
2013-09-23 7:39 ` Jörg-Volker Peetz
2013-09-22 20:31 ` Jörn Engel
2013-09-22 20:14 ` Jörn Engel
2013-09-12 21:31 ` [PATCH] /dev/random: Insufficient of entropy on many architectures Jörn Engel
2013-09-13 5:36 ` Stephan Mueller
2013-09-13 11:54 ` Thorsten Glaser
2013-09-13 19:29 ` Theodore Ts'o
2013-09-13 15:26 ` Jörn Engel
2013-09-13 18:59 ` Theodore Ts'o
2013-09-15 11:12 ` Stephan Mueller
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