From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
Eric Biggers <ebiggers@google.com>, Theodore Ts'o <tytso@mit.edu>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] random: vary jitter iterations based on cycle counter speed
Date: Wed, 13 Jul 2022 16:40:17 +0200 [thread overview]
Message-ID: <Ys7ZURKkoHw8Bp+q@zx2c4.com> (raw)
In-Reply-To: <eb74e1b8-af7e-21e8-658f-af6c7975264e@arm.com>
Hi Vladimir,
On Wed, Jul 13, 2022 at 03:31:05PM +0100, Vladimir Murzin wrote:
> I've just seen on the platform with slow(ish) timer that it is now considered
> as a source of entropy with samples_per_bit set to 27 (5.19-rc6 has MAX_SAMPLES_PER_BIT
> set to 32). Because of that I see significant delays and I'm trying to understand what
> could be wrong with my setup.
>
> I observe one credit_init_bits(1) call (via entropy_timer()) per ~970 schedule() calls.
> Is that somewhat expected? Does it make sense at all?
How slow are we talking? Seconds? Minutes? Is it too slow? It's possible
that MAX_SAMPLES_PER_BIT=32 is a bit high as a threshold and I should
reduce that a bit.
Also, out of curiosity, why is your timer so slow?
Jason
next prev parent reply other threads:[~2022-07-13 14:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-22 13:20 [PATCH] random: vary jitter iterations based on cycle counter speed Jason A. Donenfeld
2022-07-13 14:31 ` Vladimir Murzin
2022-07-13 14:40 ` Jason A. Donenfeld [this message]
2022-07-13 14:52 ` Vladimir Murzin
2022-07-13 14:53 ` Jason A. Donenfeld
2022-07-13 15:11 ` [PATCH] random: cap jitter samples per bit to factor of HZ Jason A. Donenfeld
2022-07-13 15:52 ` Vladimir Murzin
2022-07-13 16:21 ` Jason A. Donenfeld
2022-07-16 17:45 ` Linus Torvalds
2022-07-16 18:09 ` Jason A. Donenfeld
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Ys7ZURKkoHw8Bp+q@zx2c4.com \
--to=jason@zx2c4.com \
--cc=ebiggers@google.com \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=tytso@mit.edu \
--cc=vladimir.murzin@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox