Re: Raspberry Pi 5 and PREEMPT_RT (6.13.0-rc3)

[Tim Sander <tim@krieglstein.org>]

Hi

Just my 2 ct.

Am Mittwoch, 8. Januar 2025, 10:48:56 CET schrieb Florian Paul Schmidt:
> Hi!
> 
> On 1/7/2025 3:39 PM, Sebastian Andrzej Siewior wrote:
> > On 2024-12-20 14:18:43 [+0100], Florian Paul Schmidt wrote:
> [...]
> 
> > The backtrace appears long but everything up to folios_put_refs()
> > appears preemtible. Then there is the interrupt handler. This looks
> > okay.
> 
> That was my impression as well. Nothing really surprising (at least for
> my limited knowledge in these matters.)
> 
> > Based on this trace, I don't see a section which disables preemption/
> > interrupts and be the reason for the interrupt happening.
> > 
> > One thing that could delay your doing are small caches.
> > Then there is looking within the system: An inaccurate/ low resolution
> > clocksource and/ or timer device.
It could also be the TLB infrastructure. I found that these events can also be 
very time consuming, probably combined with memory contention?
I think this might be traced with performance counters but i never looked into 
this further than musing about the possibility.

Best regards
Tim