Re: crypto: caam from tasklet to threadirq

On Tue, 20 Sep 2016, Russell King - ARM Linux wrote:

which corresponds to an 8% slowdown for the threaded IRQ case.  So,
tasklets are indeed faster than threaded IRQs.

Fair enough.

I've tried to perf it, but...
 ....

So, sorry, I'm not going to bother trying to get any further with this.
If the job was not made harder stupid hardware design and kernel
politics, then I might be more inclined to do deeper investigation, but
right now I'm finding that I'm not interested in trying to jump through
these stupid hoops.

I'd be very interested in a sched_switch + irq + softirq trace which does
not involve PMU hardware for both irqthreads and tasklets, but I can
understand if you can't be bothered to gather it.

Vs. the PMU interrupt thing. What's the politics about that? Do you have
any pointers?
 

I think I've proven from the above that this patch needs to be reverted
due to the performance regression, and that there _is_ most definitely
a deterimental effect of switching from tasklets to threaded IRQs.

I agree that the revert should happen, but I'd rather see a bit more
information why this regression happens with the switch from tasklets to
threaded irqs.

Thanks,

	tglx