Am 10.07.2015 um 11:46 schrieb Gilles Chanteperdrix:
On Fri, Jul 10, 2015 at 11:34:59AM +0200, Johann Obermayr wrote:
Am 09.07.2015 um 17:51 schrieb Gilles Chanteperdrix:
On Thu, Jul 09, 2015 at 05:43:03PM +0200, Johann Obermayr wrote:
Am 09.07.2015 um 16:19 schrieb Gilles Chanteperdrix:
On Thu, Jul 09, 2015 at 02:15:55PM +0200, Johann Obermayr wrote:
Hello,
we have follow situation
u64 lrtdrv_time_of_irq_ns ;
void worker_task()
{
while(1)
{
rtdm_task_sleep_abs(lrtdrv_time_of_irq_ns + 950000ull,
RTDM_TIMERMODE_ABSOLUTE);
do_something();
}
}
_kernel_rtdm_irq_handler()
{
lrtdrv_time_of_irq_ns = rtdm_clock_read_monotonic();
}
the _kernel_irq_callback() is called every 1ms.
we will , that the worker_task begin 50us before next irq
But sometime, the worker task start ~50us after irq. Why ?
Best way to know, enable the I-pipe tracer, setup sufficient back
trace points, and when the wrong wake up happens, trigger an I-pipe
trace.
i will enable i-pipe tracer.
found out, that
rtdm_task_sleep_abs(xxx, RTDM_TIMERMODE_ABSOLUTE);
u64 calc = rtdm_clock_read_monotonic();
sometime the diff between xxx & calc is biger than 61000ns.
This is called "kernel task scheduling latency". It can be measured by
the latency -t 1 test.
Ok, i will test it with this test.
Here a simple list of measure from rtdm_task_sleep_abs(xxx) calc =
rtdm_clock_read_monotonic
Yeah, latency -t 1 does that too. Only much better.
Result a) only latency -t 1
RTT| 00:00:01 (in-kernel periodic task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat
best|--lat worst
RTD| -2.618| -2.481| -2.384| 0| 0| -2.618| -2.384
RTD| -2.506| -2.477| -2.301| 0| 0| -2.618| -2.301
RTD| -2.590| -2.479| -2.192| 0| 0| -2.618| -2.192
RTD| -2.517| -2.489| -2.324| 0| 0| -2.618| -2.192
RTD| -2.612| -2.490| -2.335| 0| 0| -2.618| -2.192
RTD| -2.723| -2.490| -2.300| 0| 0| -2.723| -2.192
RTD| -2.521| -2.491| -2.332| 0| 0| -2.723| -2.192
RTD| -2.624| -2.492| -2.346| 0| 0| -2.723| -2.192
RTD| -2.520| -2.490| -2.341| 0| 0| -2.723| -2.192
RTD| -2.584| -2.490| -2.353| 0| 0| -2.723| -2.192
RTD| -2.521| -2.487| -2.333| 0| 0| -2.723| -2.192
RTD| -2.521| -2.490| -2.329| 0| 0| -2.723| -2.192
RTD| -2.519| -2.488| -1.946| 0| 0| -2.723| -1.946
RTD| -2.521| -2.490| -2.353| 0| 0| -2.723| -1.946
RTD| -2.605| -2.490| -2.343| 0| 0| -2.723| -1.946
RTD| -2.521| -2.490| -2.328| 0| 0| -2.723| -1.946
RTD| -2.568| -2.489| -2.337| 0| 0| -2.723| -1.946
RTD| -2.520| -2.490| -2.329| 0| 0| -2.723| -1.946
RTD| -2.553| -2.491| -2.337| 0| 0| -2.723| -1.946
RTD| -2.521| -2.491| -2.325| 0| 0| -2.723| -1.946
RTD| -2.521| -2.490| -2.341| 0| 0| -2.723| -1.946
Result b) with our application, that copy with a releaxed task from/to a
SRAM on a PCI Card.
RTT| 00:00:01 (in-kernel periodic task, 100 us period, priority 99)
RTH|---lat min|---lat avg|----lat max|-overrun|---msw|---lat best|--lat
worst
RTD| -2.680| -1.537| 716.496| 38| 0| -2.680| 716.496
RTD| -2.680| -1.414| 691.232| 81| 0| -2.680| 716.496
RTD| -3.051| -0.877| 739.939| 120| 0| -3.051| 739.939
RTD| -2.662| -1.422| 738.747| 160| 0| -3.051| 739.939
RTD| -2.713| -1.637| 726.880| 191| 0| -3.051| 739.939
RTD| -2.656| -1.044| 675.880| 218| 0| -3.051| 739.939
RTD| -2.655| -1.269| 753.354| 251| 0| -3.051| 753.354
RTD| -2.661| -1.344| 633.684| 301| 0| -3.051| 753.354
RTD| -2.663| -1.626| 698.008| 333| 0| -3.051| 753.354
RTD| -2.662| -0.579| 751.352| 379| 0| -3.051| 753.354
RTD| -2.669| -1.455| 733.275| 410| 0| -3.051| 753.354
RTD| -2.758| -1.670| 629.569| 434| 0| -3.051| 753.354
RTD| -2.760| -1.686| 690.451| 445| 0| -3.051| 753.354
RTD| -2.668| -1.032| 753.099| 483| 0| -3.051| 753.354
RTD| -2.661| -1.476| 735.519| 518| 0| -3.051| 753.354
RTD| -2.660| -1.647| 725.828| 552| 0| -3.051| 753.354
RTD| -2.661| -1.236| 250.879| 556| 0| -3.051| 753.354
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