[ECOS] Query about eCos scheduler

[ECOS] Query about eCos scheduler

[Ravi Joshi]

Dear all,

I have following queries on eCos scheduler.

1. Which scheduler is being used in eCos(MLQ or bitmap)?

2. Is there any place to trace this in the kernel?

3. I remember reading in eCos reference manual that bitmap scheduler doesn't allow multiple threads running on the same priority level, what is the effect if user tries to run multiple threads running at the same priority level? does any thread starts running?

4. Anybody has clue on what happens if user tries to run multiple threads on the same priority with MLQ scheduler?
Which thread will get to run first and when will the other threads run? this is because all threads have the same priority and scheduler can schedule only one thread at a time.

Any answers will be highly appreciated.

Thanks,
-Ravi

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Re: [ECOS] Query about eCos scheduler

[Nick Garnett]

"Ravi Joshi" <ravijoshi@operamail.com> writes:

> Dear all,
> 
> I have following queries on eCos scheduler.
> 
> 1. Which scheduler is being used in eCos(MLQ or bitmap)?

The default is the MLQ scheduler.

> 
> 2. Is there any place to trace this in the kernel?
>

You can turn on instrumentation. This will give you a trace of
important events in the kernel. You have to interpret the contents of
the instrumentation buffer yourself, however.

> 3. I remember reading in eCos reference manual that bitmap scheduler
> doesn't allow multiple threads running on the same priority level,
> what is the effect if user tries to run multiple threads running at
> the same priority level? does any thread starts running?
>

If the application tries to create a thread at a priority that is
already occupied, then it creates it at the next available lower
priority.

> 4. Anybody has clue on what happens if user tries to run multiple
> threads on the same priority with MLQ scheduler?  Which thread will
> get to run first and when will the other threads run? this is
> because all threads have the same priority and scheduler can
> schedule only one thread at a time.
>

The threads will be run in the order in which they were created. If
timeslicing is enabled then the scheduler will switch to the next
thread at each timeslice point.

-- 
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com      The eCos and RedBoot experts


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Re: [ECOS] Query about eCos scheduler

[mohanlal jangir]

> > 4. Anybody has clue on what happens if user tries to run multiple
> > threads on the same priority with MLQ scheduler?  Which thread will
> > get to run first and when will the other threads run? this is
> > because all threads have the same priority and scheduler can
> > schedule only one thread at a time.
> >
>
> The threads will be run in the order in which they were created. If
> timeslicing is enabled then the scheduler will switch to the next
> thread at each timeslice point.
>
Does it mean, if timeslicing is not enabled then only first created thread
will run and others do not run at all?

Regards
Mohanlal

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Re: [ECOS] Query about eCos scheduler

[Gary Thomas]

On Fri, 2003-09-12 at 21:54, mohanlal jangir wrote:
> > > 4. Anybody has clue on what happens if user tries to run multiple
> > > threads on the same priority with MLQ scheduler?  Which thread will
> > > get to run first and when will the other threads run? this is
> > > because all threads have the same priority and scheduler can
> > > schedule only one thread at a time.
> > >
> >
> > The threads will be run in the order in which they were created. If
> > timeslicing is enabled then the scheduler will switch to the next
> > thread at each timeslice point.
> >
> Does it mean, if timeslicing is not enabled then only first created thread
> will run and others do not run at all?

Yes, if timeslicing is not enabled, then the highest priority thread
will run until it does something which blocks, e.g. sleeps waiting 
for a semaphore.  In this case, the system would be purely event driven.

-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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