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Date:   Fri, 14 Aug 2020 18:17:56 +0200
From:   Sedat Dilek <>
To:     Willy Tarreau <>
Cc:     George Spelvin <>, Amit Klein <>,
        Eric Dumazet <>,
        "Jason A. Donenfeld" <>,
        Andy Lutomirski <>,
        Kees Cook <>,
        Thomas Gleixner <>,
        Peter Zijlstra <>,
        Linus Torvalds <>,
Subject: Re: [DRAFT PATCH] random32: make prandom_u32() output unpredictable

On Fri, Aug 14, 2020 at 6:05 PM Willy Tarreau <> wrote:
> On Fri, Aug 14, 2020 at 05:32:32PM +0200, Sedat Dilek wrote:
> > commit 94c7eb54c4b8e81618ec79f414fe1ca5767f9720
> > "random32: add a tracepoint for prandom_u32()"
> >
> > ...I gave Willy's patches a try and used the Linux Test Project (LTP)
> > for testing.
> Just FWIW today I could run several relevant tests with a 40 Gbps NIC
> at high connection rates and under SYN flood to stress SYN cookies.
> I couldn't post earlier due to a net outage but will post the results
> here. In short, what I'm seeing is very good. The only thing is that
> the noise collection as-is with the 4 longs takes a bit too much CPU
> (0.2% measured) but if keeping only one word we're back to tausworthe
> performance, while using siphash all along.
> The noise generation function is so small that we're wasting cycles
> calling it and renaming registers. I'll run one more test by inlining
> it and exporting the noise.
> So provided quite some cleanup now, I really think we're about to
> reach a solution which will satisfy everyone. More on this after I
> extract the results.

Great news!

Will you publish your new version in [1]?

- Sedat -


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