TMS320C6657: OS kernel: Task_sleep and resolution of nticks

tam tran

Part Number: TMS320C6657
Other Parts Discussed in Thread: SYSBIOS

Hi TI

Can you please help:

1. I have problem to understand the OS kernel interface using the Task_sleep.

More exactly: to understand the "nticks" in relation to the "system clock" mentioned in the description of the kernel interface.

I'm using the keystone C6657 DSP with 1GHz as input clock . What is the "system clock" in this case?

If I would like to have a Task_sleep of, let's say, 1ms: what is the correct value of "nticks"

2. Another question: for the context of task switch's how many clock cycles (or micro sec.) do SYSBIOS take to do a task switch between 2 tasks ?

Can you please help to clarify these problems.

Attached: TI's implementation of Task_sleep(UInt32 nticks)

Tam Tran

******************* SYSBIOS intf. ********************

Void Task_sleep(UInt32 nticks);

ARGUMENTS

nticks — number of system clock ticks to sleep

DETAILS

Task_sleep changes the current task's mode from Mode_RUNNING to Mode_BLOCKED, and delays its execution for nticks increments of the system clock. The actual time delayed can be up to 1 system clock tick less than nticks due to granularity in system timekeeping and the time elapsed per tick is determined by Clock_tickPeriod.

After the specified period of time has elapsed, the task reverts to the Mode_READY mode and is scheduled for execution.

A task switch always occurs when calling Task_sleep if nticks > 0.

CONSTRAINTS

Task_sleep cannot be called from a Swi or Hwi, or within a disable / restore block.

Task_sleep cannot be called from the program's main() function.

Task_sleep should not be called from within an Idle function. Doing so prevents analysis tools from gathering run-time information.

nticks cannot be BIOS_WAIT_FOREVER.

over 3 years ago

0 Shankari G over 3 years ago

TI__Mastermind 25535 points

Tam tran,

Your understanding on the "Task_sleep" is correct.

-----

For example, If we pass "1" as a parameter to the Task_sleep function, it "will delay the execution of the current task by 1 ms".

Task_sleep(1); ---> It will block the current Running task for 1 ms..and allow the main task to run...

For Task_sleep ( 2 ) --> It will block the current Running task for 2 ms..and allow the main task to run...

----

nticks means the number of ticks.

For example, -----Time tick----- calculation for DSP running 1 GHz...

Total no of CPU cycles = cycles or ticks

DSP core frequency = 1000 MHz ---- that is --> 1 GHz

Time = 1 / Freq ( General formula )

= 1 / 1000 MHz ( DSP core frequency )

= 0.001 us ( Micro seconds)

1000000000 cycles = 1 sec

( Please note, cycles and ticks are one and the same)

AND hence, 1000000000 ticks per second

------------------

If you are looking for the exact time stamp,

1. you can use utilReadTime32() before and after the code

2. subtract the two values.

3. Convert the cycles/ticks into time like below:

1000000000 cycles = 1 sec

=>32149501 cycles = 0.032 sec

Regards

Shankari G

0 tam tran over 3 years ago in reply to Shankari G

Intellectual 600 points

Many thanks for you support Shankari

Can you please answer my 2. question as well:

2. Another question: for the context of task switch's how many clock cycles (or micro sec.) in average do SYSBIOS take to do a task switch between 2 tasks ?

Tam Tran

+1 Shankari G over 3 years ago in reply to tam tran

TI__Mastermind 25535 points

Tam tran,

Second question was also answered.

We have to calculate that --- > clock cycles that the SYSBIOS take during the task switch....

Use utilReadTime32() and calculate the clock cycles, during the task switch.

----

For cycle time, I use the following methods.

================

This will make use of the clock ticks/cycles of DSP core running at 1000 MHz and it will be precise...

Here you go.....

=================

Code snippet:

//Shankari-Start-Declaration for time ticks

#include "C:\ti\pdk_keystone2_3_01_04_07\packages\ti\csl\csl_tsc.h"

//<ti/csl/csl_tsc.h>

extern uint32_t utilReadTime32();

//Shankari-End-Declaration for time ticks

......

/*Throughput calculation initialization */

unsigned int StartTime = 0;
unsigned int EndTime = 0;
unsigned int Total_cycle_ticks = 0;

/*Throughput calculation initialization Ends */

.......

//Usage

StartTime = utilReadTime32(); // ----------------------- Start time

// Please insert your code here ------------

sauConnDmPktTest(tf, pat,
100, /* Number of packets per connection */
512, /* initial payload length */
0, /* payload llength increment step */
SAU_PAYLOAD_INC8 /* payload pattern */
);

EndTime = utilReadTime32(); // -------------------------- End time

Total_cycle_ticks = EndTime-StartTime; // -------------------Subtract End time and start time ---- you will get the clock cycles ----- convert into seconds...

System_printf("StartTime = %d \n", StartTime);
System_printf("EndTime = %d \n", EndTime);

System_printf("Total_cycle_ticks = %d \n", Total_cycle_ticks);

// System_printf(" sauConnDmPktTest 2048 PacketSize, 100 packets -Total_cycle_ticks = %d \n", Total_cycle_ticks);

------------------

Time tick calculation , you can use according to the number of Total_cycle_ticks, you get......

Total no of CPU cycles = cycles

DSP core frequency = 1000 MHz

Time = 1 / Freq ( General formula )

= 1 / 1000 MHz ( DSP core frequency )

= 0.001 us ( Micro seconds)

1000000000 cycles = 1 sec

=>32149501 cycles = 0.032 sec

---------------------------

Regards

Shankari G

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TMS320C6657: OS kernel: Task_sleep and resolution of nticks