Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting

[Thomas Gleixner]

peterz@xxxxxxxxxxxxx writes:
> On Wed, Aug 05, 2020 at 02:56:49PM +0100, Valentin Schneider wrote:
>
>> I've been tempted to say the test case is a bit bogus, but am not familiar
>> enough with the RT throttling details to stand that ground. That said, from
>> both looking at the execution and the stress-ng source code, it seems to
>> unconditionally spawn 32 FIFO-50 tasks (there's even an option to make
>> these FIFO-99!!!), which is quite a crowd on monoCPU systems.
>
> Oh, so it's a case of: we do stupid without tuning and the system falls
> over. I can live with that.

It's not a question of whether you can live with that behaviour for a
particular silly test case.

The same happens with a single RT runaway task with enough interrupt
load on a UP machine. Just validated that. And that has nothing to do
with a silly test case. Sporadic runaways due to a bug in a once per
week code path simply can happen and having the safety net working
depending on a config option selected or not is just wrong.

Thanks,

        tglx