Re: rt20 scheduling latency testcase and failure data

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* Darren Hart <[email protected]> wrote:

> yet to see a missed period with the version of the program.  While 
> getting to this point, I did see some things that concerned me:
> 
> sched_la-4856  3D... 4083us!: math_state_restore (device_not_available)
> sched_la-4856  3D... 16033us : smp_apic_timer_interrupt (4b3b98e8 0 0)
> 
> Am I reading that right?  12ms to complete math_state_restore()?  What 
> does "device_not_available" mean here?

no - the kernel returned to userspace after doing the 
math_state_restore, and the next thing you saw is the timer IRQ. The 
tracer traces function entries, but not function exits.

> Here are some other similar traces:
> 
> sched_la-5008  2D... 4104us!: math_state_restore (device_not_available)
> sched_la-5008  2.... 4992us > sys_clock_gettime (00000001 b7fc8378 0000007b)

same here: we returned to userspace after FPU restore, and the next 
thing was a sys_clock_gettime() syscall ~800 usecs later.

	Ingo
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