From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Cristian Rodríguez" <cristian@rodriguez.im>,
"Florian Weimer" <fweimer@redhat.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
Wilco Dijkstra <Wilco.Dijkstra@arm.com>,
GNU C Library <libc-alpha@sourceware.org>,
"Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: Re: [PATCH 2/2] Add single-threaded fast path to rand()
Date: Thu, 21 Mar 2024 15:07:37 +0000 [thread overview]
Message-ID: <ZfxNOZSS9V52mlt8@arm.com> (raw)
In-Reply-To: <8cf180c9-f7e9-4a32-86a4-a5780131ec87@efficios.com>
The 03/21/2024 10:35, Mathieu Desnoyers wrote:
> On 2024-03-21 09:33, Cristian Rodríguez wrote:
> > Afaik the other path that hasn't been tried is rseq no ? could the
> > kernel provide a random state this way that it is cleared on the right
> > conditions..
>
> Letting rseq know about userspace random state would add a lot of coupling
> between kernel and userspace. I wonder if we can achieve the speed up you
> are looking for using existing rseq/membarrier features.
>
> At the last GNU Cauldron, I created a biased locking prototype for Florian
> based on rseq:
...
i think rand() should be a 2 line function, without any
locking, since it is *not* required to be thread-safe nor
crypto quality.
but i guess for glibc it's safer to keep the current
implementation just with single-thread checks.
either way, it is not the best candidate for rseq
optimizations, as that complexity is not justified, to
speed up code with undefined behaviour..
next prev parent reply other threads:[~2024-03-21 15:08 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-18 15:20 Wilco Dijkstra
2024-03-18 19:24 ` Cristian Rodríguez
2024-03-19 15:44 ` Wilco Dijkstra
2024-03-20 12:31 ` Adhemerval Zanella Netto
2024-03-20 14:18 ` Cristian Rodríguez
2024-03-20 14:27 ` Adhemerval Zanella Netto
2024-03-21 7:39 ` Florian Weimer
2024-03-21 13:33 ` Cristian Rodríguez
2024-03-21 14:35 ` Mathieu Desnoyers
2024-03-21 15:07 ` Szabolcs Nagy [this message]
2024-03-21 15:18 ` Wilco Dijkstra
2024-03-21 15:53 ` Adhemerval Zanella Netto
2024-03-22 14:27 ` Zack Weinberg
2024-03-22 14:46 ` Adhemerval Zanella Netto
2024-03-22 15:30 ` Zack Weinberg
2024-03-22 18:05 ` Adhemerval Zanella Netto
2024-03-22 19:47 ` Mathieu Desnoyers
2024-03-22 22:54 ` Cristian Rodríguez
2024-03-23 14:01 ` Zack Weinberg
2024-03-23 15:23 ` Mathieu Desnoyers
2024-03-25 14:09 ` Mathieu Desnoyers
2024-03-25 17:52 ` Adhemerval Zanella Netto
2024-03-24 0:59 ` Cristian Rodríguez
2024-03-25 6:44 ` Florian Weimer
2024-03-20 14:28 ` Wilco Dijkstra
2024-03-20 14:40 ` Xi Ruoyao
-- strict thread matches above, loose matches on Subject: below --
2023-11-28 17:37 Wilco Dijkstra
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