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From:   Stephan Mueller <smueller@chronox.de>
To:     Torsten Duwe <duwe@lst.de>
Cc:     Willy Tarreau <w@1wt.eu>, "Theodore Y. Ts'o" <tytso@mit.edu>,
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        Matthew Garrett <mjg59@srcf.ucam.org>,
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        Lennart Poettering <mzxreary@0pointer.de>,
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        Randy Dunlap <rdunlap@infradead.org>,
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        Eric Biggers <ebiggers@kernel.org>,
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        Petr Tesarik <ptesarik@suse.cz>
Subject: Re: [PATCH v36 00/13] /dev/random - a new approach
Date:   Tue, 10 Nov 2020 11:22:14 +0100
Message-ID: <34318060.ATrlOLLGV9@tauon.chronox.de>
In-Reply-To: <3073852.aeNJFYEL58@positron.chronox.de>
References: <20200921075857.4424-1-nstange@suse.de> <20201016172619.GA18410@lst.de> <3073852.aeNJFYEL58@positron.chronox.de>
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Am Montag, 19. Oktober 2020, 21:28:50 CET schrieb Stephan M=FCller:

Hi,
>=20
> * Performance
>=20
>  - Faster by up to 75% in the critical code path of the interrupt handler
>    depending on data collection size configurable at kernel compile time -
>    the default is about equal in performance with existing /dev/random as
>    outlined in [2] section 4.2.

By streamlining the implementation a bit, the LRNG interrupt handler now=20
operates about 130% faster than the existing /dev/random (average of 97 cyc=
les=20
of the existing /dev/random code vs. an average of 42 cycles of the LRNG).=
=20
This fast operation is the default now due to patch [2]. The conceptual dat=
a=20
handling outlined in [3] section 2.2 remains unchanged.

Even the addition of health tests applied to the noise source data would st=
ill=20
result in a faster interrupt handling code (average of 97 cycles of the=20
existing /dev/random code vs on average 78 cycles of the LRNG).

[1] https://github.com/smuellerDD/lrng/commit/
10b74b242950371273e38df78060e258d9d3ea40

[2] https://github.com/smuellerDD/lrng/commit/
383b087653c21cf20984f5508befa57e96f685ba

[3] https://chronox.de/lrng/doc/lrng.pdf

Ciao
Stephan