Re: rt20 scheduling latency testcase and failure data

[Ingo Molnar]

* Darren Hart <dvhltc@xxxxxxxxxx> 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/