On 05/19/2013 11:51 AM, Amit Kucheria wrote:
Similarly, the SCHED_DEADLINE patches shouldn't affect default runtime 
scheduler behaviour unless a task uses the DEADLINE policy.


Right, SCHED_DEADLINE is only one more scheduling policy you can
use (as SCHED_FIFO/RR). If you don't use it the scheduler isn't
affected.

However, I haven't studied the intersection of the Preempt RT and 
SCHED_DEADLINE patches in source form yet. If they touch common pieces of code, 
merging both in might be an ongoing effort. Juri, do you know?


I started maintaining the patchset working on an implementation
based on PREEMPT_RT, then we switched back as the main goal was
mainline inclusion (and we didn't have real needs to be based
on PREEMPT_RT). Anyway, the intersection was pretty clean, only
minor modifications were needed to run SCHED_DEADLINE on top of
PREEMPT_RT.

Best,

- Juri


On Fri, May 17, 2013 at 8:11 PM, Mark Orvek <mark.or...@linaro.org 
<mailto:mark.or...@linaro.org>> wrote:

    The PREEMPT_RT patchset is configurable.  I believe the default is 
PREEMPT_DESKTOP which is what most MV CGE customers use.  Another config 
options is PREEMPT_NONE but I believe its usage is rare.

    Mark


    On Fri, May 17, 2013 at 7:25 AM, Patrick MacCartee <pmaccar...@mvista.com 
<mailto:pmaccar...@mvista.com>> wrote:

        Will these be added in a way that makes them easy to remove? Many, >95% 
don't use Preempt RT in Linux as it impacts network performance and makes things 
very temperamental.  You would think people would just disable this RT, but when 
trying to isolate issues it adds another variable to the mix. I believe Yocto has 
a way of adding and removing RT patches that is some what straight forward and 
preferable based on feedback from OEM's.

        Just a thought,
        Patrick


        On Fri, May 17, 2013 at 6:34 AM, Mike Holmes <mike.hol...@linaro.org 
<mailto:mike.hol...@linaro.org>> wrote:

            In LNG you could end up with an interesting mix of preempt RT and 
deadline patches making the analysis and benchmarking interesting to interpret.
            In addition there are discussions about adding zero overhead linux 
(ZOL) like features.

            Mike



            On Friday, May 17, 2013 6:08:20 AM UTC-4, David Rusling wrote:

                Amit,
                     an interesting proposal.  I think that most of the LNG 
steering committee is on this alias, but just in case, I'm adding them to it...
                Dave

                Amit Kucheria
                17 May 2013 10:15
                Hi all,

                As part of our investigations into the Linux scheduler we've
                interacted with Juri Lelli at the University of Pisa (cc'ed) 
who is
                part of a group that is working on a DEADLINE scheduler[1] for
                Linux[2].

                While we're coming at this from a power managment angle[3], I 
suspect
                that LEG and LNG already have real-world usecases that would 
benefit
                from deadline scheduler found in other RTOSes.

                So I think it makes sense to merge Juri's tree into 
linux-linaro going
                forward to allow easier experimentation. Does LEG and LNG have 
any
                interest in this at this point?

                Juri has expressed an interest in maintaining a current branch 
of the
                code that could be merged into our monthly release. In return, 
real
                world usecases will improve his chances of getting the code 
merged
                into mainline.

                Regards,
                Amit

                [1] http://retis.sssup.it/?q=node/__35 
<http://retis.sssup.it/?q=node/35>
                [2] https://lkml.org/lkml/2013/2/__11/373 
<https://lkml.org/lkml/2013/2/11/373>
                [3] Mostly involving discussions at this point, no real 
engineering
                effort invested yet

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                Linaro: The future of Linux on ARM




        --
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        MontaVista Software LLC
        fone: 408-572-7937 <tel:408-572-7937>
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