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

[Jason A. Donenfeld]

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?

Jason