Hi Oak,

What frequency are you running the CPU at? The default is 800MHz.

8000000 / 800MHz = 10ms

 - Alex

On Thu, 2017-10-19 at 21:41 -0700, Norrathep Rattanavipanon wrote:
> Yes, ideally we would want to run our experiments on the RT branch.
> But given the close deadline, i'd rather do it on the master branch,
> which I'm more familiar, and we can still keep the formally verified
> property :).
>
> We kind of want to simulate a quick and simple real-time scheduling
> in the master branch.
> Basically, the main thread wants to run a long task but we dont want
> it to hoard all resources. So we split it into a bunch of smaller
> tasks. Then, for a security reason, we want to run each of the
> smaller tasks atomically. One way I can think of is to temporarily
> raise the priority of the main thread when running each task and
> yield once a task is finished.  The goal is to complete the long task
> ASAP while allowing other processes to run if needed. I then want to
> see how much time other processes can use between two tasks.
>
> Oak
>
>
>
> On Thu, Oct 19, 2017 at 6:06 PM, <Anna.Lyons@data61.csiro.au> wrote:
> >
> > Recall I stated that the scheduler is basic ;)
> >
> > The timer ticks on the master kernel are started on boot, then not
> > reset on any thread operation. This means that the actual thread
> > timeslice is just 'X interrupts must come in'. So it's likely to
> > vary by up to the tick ms value, as the yield does not have any
> > relation with a new tick starting.
> >
> > If you measured the time for many threads (100 or so) to all
> > consumer their timeslice, you should see the error drop off and the
> > average value approach the timeslice.  
> >
> > I'm curious as to what exactly you are trying to do? the RT kernel
> > may be more suited.
> >
> > Thanks
> > Anna. 
> >

> > From: Norrathep Rattanavipanon <nrattana@uci.edu>
> > Sent: Friday, 20 October 2017 11:52 AM
> >
> > To: Lyons, Anna (Data61, Kensington NSW)
> > Cc: devel@sel4.systems
> > Subject: Re: [seL4] Questions on seL4's scheduling
> >  
> > Thanks Anna. So I tried to measure timeslice in userspace and it
> > seems like it does not match with the settings. Any idea what
> > happens or what is wrong with my code:
> > I ran it on IMX6-SabreLite, master branch/kernel version 4.0.
> >
> > main thread:
> > sel4bench_init();
> > seL4_Yield();
> > uint64_t start = sel4bench_get_cycle_count();
> > seL4_Yield();
> > uint64_t end = sel4bench_get_cycle_count();
> > sel4bench_destroy();
> > printf("Takes %llu\n", (end-start));
> >
> > second thread:
> > while(1);
> >
> > Both of them have the same priority.
> >
> > When I set TIMER_TICK_MS=5 and TIME_SLICE=2, it outputs 8000000,
> > which is around 8msecs.
> > Also, if i set TIMER_TICK_MS=2 and TIME_SLICE=1, I get around
> > 1.6msecs.
> >
> > Best,
> >
> > On Thu, Oct 19, 2017 at 5:03 PM, <Anna.Lyons@data61.csiro.au>
> > wrote:
> > > Hi Oak,
> > >
> > > The timeslice value on the master kernel is only reset on thread
> > > creation and once the thread is depleted, so when a thread drops
> > > its priority the timeslice will not change, so it'll run for 2ms.
> > >
> > > The timeslice cannot be set to lower than 1 ms, however you could
> > > change the timer driver on your target platform to do so (look at
> > > the initTimer function).
> > >
> > > Note that the scheduler on the master kernel is fairly basic, the
> > > RT branch is far more fully featured (tickless and you can set
> > > different timeslices per thread). 
> > >
> > > Cheers
> > > Anna. 
> > >

> > > From: Norrathep Rattanavipanon <nrattana@uci.edu>
> > > Sent: Friday, 20 October 2017 10:18 AM
> > > To: Lyons, Anna (Data61, Kensington NSW)
> > > Cc: devel@sel4.systems
> > > Subject: Re: [seL4] Questions on seL4's scheduling
> > >  
> > > Also, is it possible to set timeslice to be less than 1
> > > milliseconds?
> > >
> > > On Thu, Oct 19, 2017 at 3:08 PM, Norrathep Rattanavipanon <nratta
> > > na@uci.edu> wrote:
> > > > Thank you, Anna and Gernot for the answer.
> > > >
> > > > One more question, so assuming a timeslice is 5ms, a thread
> > > > with the highest priority has run for 3ms, then drops its
> > > > priority to be the same as the other thread.
> > > > Then, the same thread will start running with the fresh
> > > > timeslice and it will run for another 5ms or will it just run
> > > > for 2ms to complete the timeslice?
> > > >
> > > > Oak
> > > >
> > > > On Mon, Oct 16, 2017 at 3:09 PM, <Anna.Lyons@data61.csiro.au>
> > > > wrote:
> > > > > Hi Oak,
> > > > >
> > > > > Assuming your questions are about the master branch of the
> > > > > kernel, as on the RT branch the kernel is tickless.
> > > > >
> > > > > 1. There are two config paramters
> > > > >     + TIMER_TICK_MS is how many milliseconds per tick
> > > > >     + TIME_SLICE is how many ticks per timeslice. 
> > > > >
> > > > > 2. Assuming a thread is waiting on a notification object for
> > > > > an irq to arrive, and another thread is running at the same
> > > > > priority when the irq arrives, the thread waiting on the
> > > > > notification object will not be woken until the currently
> > > > > running thread has exhausted it's timeslice.
> > > > >
> > > > > Cheers,
> > > > > Anna. 
> > > > >  

> > > > > From: Devel <devel-bounces@sel4.systems> on behalf of
> > > > > Norrathep Rattanavipanon <nrattana@uci.edu>
> > > > > Sent: Tuesday, 17 October 2017 8:35 AM
> > > > > To: devel@sel4.systems
> > > > > Subject: [seL4] Questions on seL4's scheduling
> > > > >  
> > > > > Hello,
> > > > >
> > > > > I have a few questions about seL4's scheduling model in the
> > > > > main (formally verified) branch.
> > > > >
> > > > > 1) I see the time slice parameter in make menuconfig. Is that
> > > > > where I can change the scheduler's time slice correct? And
> > > > > the unit is in timer tick period I suppose?
> > > > >
> > > > > 2) I kind of remember the discussion we had that if an
> > > > > interrupt handler has lower priority than the currently
> > > > > running task, then the interrupt wouldnt happen. 
> > > > > So what if both of them have the same priority, would the
> > > > > kernel schedule the currently running task until it uses up
> > > > > all of its timeslice, then issues the interrupt notification
> > > > > or would the interrupting process get executed right away?
> > > > >
> > > > > Best Regards,
> > > > > Oak
> > > > >
> > > > > -- 
> > > > > Norrathep (Oak) Rattanavipanon
> > > > > M.S. in Computer Science
> > > > > University of California - Irvine
> > > > >
> > > >
> > > >
> > > > -- 
> > > > Norrathep (Oak) Rattanavipanon
> > > > M.S. in Computer Science
> > > > University of California - Irvine
> > > >
> > >
> > >
> > > -- 
> > > Norrathep (Oak) Rattanavipanon
> > > M.S. in Computer Science
> > > University of California - Irvine
> > >
> >
> >

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