Messages in this thread | | | Date | Thu, 18 May 2006 13:24:35 +0200 | From | Ingo Molnar <> | Subject | Re: rt20 scheduling latency testcase and failure data |
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* Darren Hart <dvhltc@us.ibm.com> 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.
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