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

[Thomas Gleixner]

Vladimir Oltean <olteanv@xxxxxxxxx> writes:
>>  1) When irq accounting is disabled, RT throttling kicks in as
>>     expected.
>> 
>>  2) With irq accounting the RT throttler does not kick in and the RCU
>>     stall/lockups happen.
>> 
>> Not much, but there is clearly interaction between irq time accounting
>> and scheduler accounting.
>> 
>> Can you please reduce /proc/sys/kernel/sched_rt_runtime_us in steps of
>> 50000? At least in theory, reduction should bring the throttling back.
>
> We already know from my original report that reducing
> sched_rt_runtime_us to 80% (800000) gives us a stable system.
> https://lkml.org/lkml/2020/6/4/1062

Oh. Somehow missed that. Btw, can you please use links in the form of:

    https://lore.kernel.org/r/$MSGID

lkml.org is spotty and having the message id allows to search in the
mail client as well.

> What is this telling us?

It seems that the fine grained irq time accounting affects the runtime
accounting in some way which I haven't figured out yet.

Thanks,

        tglx