From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>
Subject: Re: [PATCH] bpf: call get_random_u32() for random integers
Date: Mon, 5 Dec 2022 23:47:44 +0100 [thread overview]
Message-ID: <Y451ENAK7BQQDJc/@zx2c4.com> (raw)
In-Reply-To: <730fd355-ad86-a8fa-6583-df23d39e0c23@iogearbox.net>
On Mon, Dec 05, 2022 at 11:21:51PM +0100, Daniel Borkmann wrote:
> On 12/5/22 7:15 PM, Jason A. Donenfeld wrote:
> > Since BPF's bpf_user_rnd_u32() was introduced, there have been three
> > significant developments in the RNG: 1) get_random_u32() returns the
> > same types of bytes as /dev/urandom, eliminating the distinction between
> > "kernel random bytes" and "userspace random bytes", 2) get_random_u32()
> > operates mostly locklessly over percpu state, 3) get_random_u32() has
> > become quite fast.
>
> Wrt "quite fast", do you have a comparison between the two? Asking as its
> often used in networking worst case on per packet basis (e.g. via XDP), would
> be useful to state concrete numbers for the two on a given machine.
Median of 25 cycles vs median of 38, on my Tiger Lake machine. So a
little slower, but too small of a difference to matter.
next prev parent reply other threads:[~2022-12-05 22:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 18:15 [PATCH] bpf: call get_random_u32() for random integers Jason A. Donenfeld
2022-12-05 22:21 ` Daniel Borkmann
2022-12-05 22:47 ` Jason A. Donenfeld [this message]
2022-12-06 12:50 ` Toke Høiland-Jørgensen
2022-12-06 12:59 ` Jason A. Donenfeld
2022-12-06 13:26 ` Toke Høiland-Jørgensen
2022-12-06 13:30 ` Jason A. Donenfeld
2022-12-06 13:53 ` Toke Høiland-Jørgensen
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