Re: SCHED_DEADLINE as user

On Thu, 23 Aug 2018 15:09:57 +0200
Juri Lelli [off-list ref] wrote:

On 23/08/18 15:00, luca abeni wrote:

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On Thu, 23 Aug 2018 14:37:39 +0200
Juri Lelli [off-list ref] wrote:
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Maybe the existing system wide sched_rt_{period,
runtime}_us are enough?    

I do not know... A cgroup-based interface looks more powerful
(and not so difficult to implement... :), and would allow the
sysadmin to decide which users can use SCHED_DEADLINE, how much
SCHED_DEADLINE bandwidth can each user/group use, etc...    

How about extending PAM limits instead? It looks like it's what
(e.g.) audio users rely on already [1]. It is maybe possible to
add dlruntime, dlperiod, dldeadline parameters in there?  

Ok, I do not know much about these PAM limits... Where can I find
more information?  

The link I shared already gives some information, man pam_limits and
limits.conf also.

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What do we need to implement exactly, to add these dlruntime,
dlperiod, dldeadline parameters?  

Not sure yet "exactly" :-), but I'd say something along these lines

https://elixir.bootlin.com/linux/latest/source/kernel/sched/core.c#L4198

Ok, thanks; I think I got it: we need to extend the "rlim" array (in
signal_struct) adding fields for "RLIMIT_DLRUNTIME" and friends
(actually, I think a "RLIMIT_UTILIZATION" field is also needed). And
then we need to add checks for these fields in __sched_setscheduler(),
etc...

Maybe I am misunderstanding this stuff, but the cgroup-based approach
looks simpler / more elegant :)



			Thanks,
				Luca