Linux scheduler Implementation details

Linux scheduler Implementation details

[Sonika Sachdeva]

Hello List,

I want to simulate the Linux Scheduler, ie Calculate the priorities, counters
and define to some extent how much time a given process will take to execute on
the system. Can anyone suggest some pointers?

Thank you
Sonika

Re: Linux scheduler Implementation details

[Raj]

Sonika Sachdeva wrote:

>Hello List,
>
>I want to simulate the Linux Scheduler, ie Calculate the priorities, counters
>and define to some extent how much time a given process will take to execute on
>the system. Can anyone suggest some pointers?
>
>Thank you
>Sonika
>
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Documentation/sched-design.txt
Documentation/sched-coding.txt

and oh ofcourse, kernel/sched.c :-)

/Raj

Re: Linux scheduler Implementation details

[Nick Piggin]

Sonika Sachdeva wrote:

>Hello List,
>
>I want to simulate the Linux Scheduler, ie Calculate the priorities, counters
>and define to some extent how much time a given process will take to execute on
>the system. Can anyone suggest some pointers?
>
>

It is all in kernel/sched.c, so you can just make a simulator and
plug that code in.

This will perfectly model the scheduler behaviour given some input
from your simulator, which is what you asked for. This has nothing
to do with maximum realtime scheduling latency, of course.

Re: Linux scheduler Implementation details

[Sonika Sachdeva]

Hi,

I want to give the loaded system metrics(loadavg, io details etc) as the input to
the simulator program so that it is able to calculate the priority for any new job
that will be submitted.

Then knowing the execution time of that job in a no-load system, I am able to
compute the latency encountered becoz of the load on the system.

How can I reuse the sched.c code to do this?

Thank you
Regards
Sonika



Nick Piggin wrote:

> Sonika Sachdeva wrote:
>
> >Hello List,
> >
> >I want to simulate the Linux Scheduler, ie Calculate the priorities, counters
> >and define to some extent how much time a given process will take to execute on
> >the system. Can anyone suggest some pointers?
> >
> >
>
> It is all in kernel/sched.c, so you can just make a simulator and
> plug that code in.
>
> This will perfectly model the scheduler behaviour given some input
> from your simulator, which is what you asked for. This has nothing
> to do with maximum realtime scheduling latency, of course.

Re: Linux scheduler Implementation details

[Nick Piggin]

Sonika Sachdeva wrote:

>Hi,
>
>I want to give the loaded system metrics(loadavg, io details etc) as the input to
>the simulator program so that it is able to calculate the priority for any new job
>that will be submitted.
>
>Then knowing the execution time of that job in a no-load system, I am able to
>compute the latency encountered becoz of the load on the system.
>
>How can I reuse the sched.c code to do this?
>
>

You can use it to tell your simulator how the Linux kernel will
schedule tasks. I'm not sure exactly what you want, execution time?
latency?

Re: Linux scheduler Implementation details

[Sonika Sachdeva]

I wonder if you could give me some hints to do fair approximations (to calculate
execution time) for scheduling process?

Regards
Sonika

Nick Piggin wrote:

> Sonika Sachdeva wrote:
>
> >Hi,
> >
> >I want to give the loaded system metrics(loadavg, io details etc) as the input to
> >the simulator program so that it is able to calculate the priority for any new job
> >that will be submitted.
> >
> >Then knowing the execution time of that job in a no-load system, I am able to
> >compute the latency encountered becoz of the load on the system.
> >
> >How can I reuse the sched.c code to do this?
> >
> >
>
> You can use it to tell your simulator how the Linux kernel will
> schedule tasks. I'm not sure exactly what you want, execution time?
> latency?

Re: Linux scheduler Implementation details

[Nick Piggin]

Sonika Sachdeva wrote:

>I wonder if you could give me some hints to do fair approximations (to calculate
>execution time) for scheduling process?
>
>

Use a very simple model? Assume each runnable process gets equal
amount of the CPU.

I have no idea what you are trying to do or why, but I suspect
that the "simulator" you should be using is testing a running
kernel on a real machine. Very simple, very accurate.