[LITMUS^RT] power management with litmus-rt

[David Moncada]

Hello Björn,

thank you very much for your quick response. So, if I understand correctly, currently LITMUS-RT does not include any energy-aware scheduler but, is it possible to extend the already existing schedulers in LITMUS-RT with DVFS and sleep states functionality? Or rather one would need to develop energy-aware RT schedulers for LITMUS-RT from scratch?

About your comment on CPU hot-plugging, does it mean that LITMUS-RT won't work when turning processors off/on even if the architecture allows sleep states?

Thanks for clearing my doubts, I'm interested in both partitioned and global approaches, so extending the existing schedulers would save some work. Also, it would be nice to have an already tested platform to start working with.

Kind regards!
David Moncada

> On Nov 7, 2016, at 1:17 AM, Björn Brandenburg <bbbrandenburg at icloud.com> wrote:
> 
> FYI my reply to your email. You should sign up for the mailing list to receive all replies.
> 
> - Björn
> 
>> Begin forwarded message:
>> 
>> From: Björn Brandenburg <bbb at mpi-sws.org <mailto:bbb at mpi-sws.org>>
>> Subject: Re: [LITMUS^RT] power management with litmus-rt
>> Date: 7 November 2016 at 08:16:43 GMT+1
>> To: litmus-dev at lists.litmus-rt.org <mailto:litmus-dev at lists.litmus-rt.org>
>> 
>> On 7 Nov 2016, at 06:18, David Moncada <david_moncada at icloud.com <mailto:david_moncada at icloud.com>> wrote:
>>> 
>>> hello, my name is david moncada and i'm currently working on energy-aware real-time multiprocessor scheduling...
>>> 
>>> i'm looking for a platform in which i can implement energy-aware real-time scheduling algorithms and measure performance. i found your system on the web and, as far as i've read about it, seem to be very complete in terms of real-time scheduling algorithms.
>>> 
>>> my question is: does your system supports in some way processor voltage scaling/sleep states? it if did, it would be a very valuable tool for my work…
>> 
>> Hi David,
>> 
>> depending on your definition of “support”, LITMUS^RT does or does not support DVS and sleep states.
>> 
>> One the one hand, we do nothing to prevent or interfere with Linux’s native support for DVS and sleep states. So if Linux supports your platform, you can use LITMUS^RT to develop DVS-aware real-time schedulers.
>> 
>> On the other hand, LITMUS^RT currently does not include any DVS-aware schedulers. That is, the included schedulers were developed assuming that processor speeds are constant and that processors are always online.  For some schedulers, enabling DVS does not make a big difference (e.g., I assume our P-FP and PSN-EDF plugins will work just fine). For others, I’m not so certain (e.g., PFAIR and GSN-EDF may break or behave in unexpected ways).
>> 
>> LITMUS^RT does not support CPU hot-plugging.
>> 
>> If you end up using LITMUS^RT and  would like to contribute patches that add or improve DVS, sleep state, or hot-plugging support, I’d be very happy to consider them. 
>> 
>> Best regards,
>> Björn
>> 
> 

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