topic Task switch time in m52259 and MQX 3.8 in ColdFire/68K Microcontrollers and Processors

Task switch time in m52259 and MQX 3.8

same — Wed, 03 Oct 2012 14:15:13 GMT

Hi,

I have a m52259 board and MQX 3.8 on it.

I want to know how long is the context switch time between tasks.

I have multiple small tasks, and every task at end of its code will make another task ready and make itself suspended. But I strongly need to know the context switch time.

is there anyone know it?

Thanks everybody

Re: Task switch time in m52259 and MQX 3.8

TomE — Thu, 04 Oct 2012 03:25:04 GMT

Measure it.

I always set up a spare 16 or 32 bit hardware timer running at 1MHz. On the MCF5329 I'm using, that's one of the DMA Timers. Then any code can read "the current time in microseconds" either side of a function, event or task. It can print it, store it in a variable (for inspection in the debugger), accumulate, log or whatever you want to do.

Of course the simplest thing is to turn a LED on that is connected to a hardware pin at point "A" in your code and turn it off at point "B". You then measure the time with an oscilloscope. Make sure to measure the overhead of turning the LED on and off, as on some hardware ports it can be surprisingly slow. I've worked on a non-Freescale CPU that took 200 or more CPU clocks to write to a GPIO pin!

Tom

Re: Task switch time in m52259 and MQX 3.8

same — Thu, 04 Oct 2012 05:35:05 GMT

I found it here: https://community.freescale.com/message/107966#107966

thanks DavidS

System Parameters

Context Switch

4.30us

413.12us 1MHz

Service Interrupt and return to task

1.51us

145.40us 1MHz

System Timer/Tick Overhead

2.52us

242.40us 1MHz

Task Management

Create Task

51.02us

4.90ms 1MHz

Delete Task

174.00us

16.70ms 1MHz

Block Task

4.30us

413.12us 1MHz

Ready Task

3.73us

358.32us 1MHz

Yield Task

6.73us

646.32us 1MHz

Task Queues

Suspend Task

16.78us

1.61ms 1MHz

Suspend Task Context Switch

7.91us

758.96us 1MHz

Resume Task

6.19us

594.32us 1MHz

Resume Task Context Switch

10.48us

1.01ms 1MHz