Re: [PATCH v6] random: defer fast pool mixing to worker

[Jason A. Donenfeld]

On 2/13/22, Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
> Hey Sebastian,
>
> On Fri, Feb 11, 2022 at 6:26 PM Sebastian Andrzej Siewior
> <bigeasy@xxxxxxxxxxxxx> wrote:
>> Sure. I can do the CPU-HP notifier later one once we are done with
>> everything. I acked the v7, don't see a road block.
>
> I've been running this over the weekend and performance is generally okay.
>
> # perf top --symbols $(objdump -t
> /usr/src/linux/drivers/char/random.o|fgrep 'F .text'|awk '{print
> $6}'|tr '\n' ,) -F max -g
>
> One thing I noticed though was that add_interrupt_randomness spends
> most of its time on:
>
>     lock   xadd   %eax,0x38(%rbp)
>
> So, as expected, those atomics really need to go. Indeed we might be
> best off with the CPU hotplug notifier for setting the count back to
> zero.
>
> Do you want to prepare a patch for this? Or should I take a stab at it?

FYI, I was overwhelmed with a compulsion to try doing it myself and
posted that here
https://lore.kernel.org/lkml/20220213215343.11652-1-Jason@xxxxxxxxx/
which is now pending your review.