FIFO and Round Robin

[M_ttferrari]

Hi, I have a doubt about tasks in fifo and round robind mode.

The MQXUG says that FIFO and Round Robin mode can work together, so if you want to create a task in round robin mode, you need to set MQX_HAS_TIME_SLICE. Well, If I do it, how can I create a task to work in FIFO mode having MQX_HAS_TIME_SLICE setted?

I'm a bit confused...

Thank you

[PetrL]

Hi, FIFO and Round Robin can work together on one processor, they cannot both set for the one task.

Basically those tasks which have TIME_SLICE  flag setted are time sliced with other task on given priority.

The priority based sheduling is still working for all tasks - that means the higher prio task will be executed if needed.

PetrL

[M_ttferrari]

Hi PetrL

I know that, but I don't know how I tell to TASK_TEMPLATE that one task has time slice and another one has a FIFO schedule mode independly of priorities. Because when MQX_HAS_TIME_SLICE is setted, the last elements of TESK_TEMPLATE correspond to time slice of the task... then if you put 0 in this element, the scheduler will give a minimum task time when I want that this task work in FIFO mode not in Round Robin. Is this correct doesn't it?

Thanks.

Matt 

[JuroV]

Partially you are right. The scheduler works like this (steps):

1) Only ready queue with highest priority (queue of ready tasks with highest priorities) is considered to be run (ignore other= lower priority tasks)

2.1) Iif current task has time slice, then:

2.1.1) if current task's time slice has counted down, then reschedule to the next task - scheduling is DONE

2.2) Schedule the current task - scheduling is DONE

If the kernel was not compiled with MQX_HAS_TIME_SLICE, then remove point 2.1 Note that setting time slice 0 for a task having time slice flag set has no meaning...

[M_ttferrari]

Hi JuroV. 

I understand about how the scheduler handles the ready task. My question is, how do I declare a task to work in FIFO mode having MQX_HAS_TIME_SLICE setted?

Thanks for your anwers

[JuroV]

Just do not insert flag MQX_TIME_SLICE_TASK to the task template.

[M_ttferrari]

Thank you JuroV, Now the answer looks obvious but I didn't understand it

[JuroV · Accepted solution]

FIFO: First task in, First task out... Means that as you insert task to the queue, they are in the order processed (the time a task will run is INFINITE, or the task itself can give up CPU time). Every task is defaultly inserted in FIFO queue.

Round-Robin: The same as FIFO, but the time is NOT INFINITE: the time is restricted by NUMBER OF TICKS dedicated for the task. The task running in Round-Robin has MQX_TIME_SLICE_TASK flag set and also, number of ticks).

[jambriz]

Hi JuroV

I understand your response.

I have a question related with RR

I'm using MQX 3.7

In my main.c have

TASK_TEMPLATE_STRUCT MQX_template_list[] =
{
/* Task number, Entry point, Stack, Pri, String, Auto? */
{MAIN_TASK, Main_task, 2000, 9, "main", MQX_AUTO_START_TASK | MQX_TIME_SLICE_TASK, 0L, 2 },
{SECOND_TASK, Second_task, 2000, 9, "second", MQX_AUTO_START_TASK | MQX_TIME_SLICE_TASK, 0l, 2},
{0, 0, 0, 0, 0, 0, }
};

In mqx.h said:

/*
** Tasks with this attribute will use the time slice
** scheduler within the kernel
*/
#if MQX_HAS_TIME_SLICE
#define MQX_TIME_SLICE_TASK (0x04)
#endif

I checked the file small_ram_config.h

And I saw:

#ifndef MQX_HAS_TIME_SLICE
#define MQX_HAS_TIME_SLICE 0
#endif

I changed the value, for 1

#ifndef MQX_HAS_TIME_SLICE
#define MQX_HAS_TIME_SLICE 1
#endif

But In CodeWarrior when I saw this code

#if MQX_HAS_TIME_SLICE
#define MQX_TIME_SLICE_TASK (0x04)
#endif

it looks like desactivated

I suppose that the flag: MQX_HAS_TIME_SLICE doesn't udated by MQX, 

am I correct?

When I execute this program ( that has the 2 task )

void Main_task(uint_32 initial_data)
{
int a;
for(a=0; a< 32000 ; a++)
{
printf("hola\t");
}

void Second_task(uint_32 initial_data)

{
int a;
for(a=0; a< 32000 ; a++)
{
printf("adios\t");
}
}

Execute the program like a FIFO , it doesn't execute like Round Robin

What are the correct modifications in the config files for change to RR scheduling?

best regards

jam

[wenxue]

Hi,

I meet the same question with you. Now I have addressed it. The step is:

1)  open   <mqx_install_dir>/build/<board>/uv4/build_libs.uvmpw

1)  add    #define MQX_HAS_TIME_SLICE      1    in user_config.h

2)  Bebuild the MQX libraries(Please note that: you should Batch build)

3) Rebuild your application.