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Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC

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On 13/04/16 02:37, Bill Huey (hui) wrote:
> [Trying to resend this so that linux-kernel mailer doesn't reject it.
> ok just found plain text mode. Will cull the CC list in future
> responses]
> 
> Hi Juri,
> 
> It's not for replacing deadline first of all. I'm not fully aware of the
> kind of things being done with deadline and I would like links so that I
> have some kind of reference
> 

OK. You can find references in Documentation, in my first reply and
embedded in the ELC slides as well. Please, let me know if you need more
:-).

> The original motivation for doing this was for a number of reasons:
> 
> 1) Current FIFO/RR policies aren't exact enough for a lot of the mixed
> modern multimedia scenarios I saw working a real-world load on an Android
> like system. Insufficient feedback to interactive UX tasks that include
> things like jackd and pulse audio for low latency applications (music,
> keyboard controllers, touch events...) across a span of tasks across the
> system.
> 
> Deadline seems to be more localized to a specific application's need and
> seems to be hard to use but I'm inexperienced with it. The problems would
> benefit from a simpler solution.
> 

I'm not sure what you mean by "localized", but I believe DEADLINE should
be used more widely to service the same kind of applications you are
referring to. It's still a quite new addition to the scheduler, so it is
understandable that we still have some legacy to fight. But we can get
better in the future.

> 2) The need for a scheduler to be driven by an external interrupt from a
> number sources directly.
> 

If you use DEADLINE to service the activity an interrupt source might
trigger, I think you can already do this.

> 3) The need for a global view of the system so that power management
> decisions can be made sensibly made in multicore systems. It's not a
> scheduler alone but ideal would have more influence over power management
> decision on battery powered devices, etc...
> 

That's true. But it is also already something we currently are working on.
I don't know if you are following the schedfreq/schedutil threads [1], for
example, but there we are discussing how to integrate scheduler and
cpufreq more closely. And you might also be interested in the EAS effort
[2].

> 4) other reasons that should be in the docs but I got sick of writing
> exhaustive documentation on the matter...
> 

:-)

> That's the best I can do for now. I need to post new version with
> compilations fixes. There's a lot of problems with code regarding
> portability and other issues with the initial revision.
> 

OK. Feel free to ask if you also decide to experiment with DEADLINE and
find any problem with it.

Best,

- Juri

[1] https://lkml.org/lkml/2016/3/17/420
    https://lkml.org/lkml/2016/2/22/1037
[2] https://lkml.org/lkml/2015/7/7/754

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[PATCH RFC v0 00/12] Cyclic Scheduler Against RTC "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:30 +0200
  [PATCH RFC v0 01/12] Kconfig change "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 03/12] Add cyclic support to rtc-dev.c "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 10/12] Export SCHED_FIFO/RT requeuing functions "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 07/12] kernel/userspace additions for addition ioctl() support for rtc "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 08/12] Compilation support "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 02/12] Reroute rtc update irqs to the cyclic scheduler handler "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 12/12] Cyclic/rtc documentation "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 06/12] Add anonymous struct to sched_rt_entity "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  [PATCH RFC v0 05/12] Task tracking per file descriptor "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-12 07:40 +0200
  Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-12 08:00 +0200
    Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-12 08:10 +0200
  Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC Juri Lelli <juri.lelli@arm.com> - 2016-04-13 11:00 +0200
    Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-13 11:40 +0200
      Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC Juri Lelli <juri.lelli@arm.com> - 2016-04-13 12:10 +0200
        Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC "Bill Huey (hui)" <bill.huey@gmail.com> - 2016-04-13 12:40 +0200

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