Re: [PATCH v4 2/5] build: Hook the schedulers into Kconfig

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 09/01/16 17:50, Jonathan Creekmore wrote:
> Andrew Cooper writes:
>
>> On 08/01/16 21:22, Jonathan Creekmore wrote:
>>> +# Enable schedulers
>>> +menu "Schedulers"
>>> +	visible if EXPERT = "y"
>>> +
>>> +config SCHED_CREDIT
>>> +	bool "Credit scheduler support"
>>> +	default y
>>> +	---help---
>>> +	  The traditional credit scheduler is a general purpose scheduler.
>>> +
>>> +	  If unsure, say Y.
>>> +
>>> +config SCHED_CREDIT2
>>> +	bool "Credit2 scheduler support (EXPERIMENTAL)"
>>> +	default y
>>> +	---help---
>>> +	  The credit2 scheduler is a general purpose scheduler that is
>>> +	  optimized for lower latency and higher VM density.
>>> +
>>> +	  If unsure, say Y.
>>> +
>>> +config SCHED_RTDS
>>> +	bool "RTDS scheduler support (EXPERIMENTAL)"
>>> +	default y
>>> +	---help---
>>> +	  The RTDS scheduler is a soft and firm real-time scheduler for
>>> +	  multicore, targeted for embedded, automotive, graphics and gaming
>>> +	  in the cloud, and general low-latency workloads.
>>> +
>>> +	  If unsure, say N.
>>> +
>>> +config SCHED_ARINC653
>>> +	bool "ARINC653 scheduler support (EXPERIMENTAL)"
>>> +	default y
>>> +	---help---
>>> +	  The ARINC653 scheduler is a hard real-time scheduler for single
>>> +	  cores, targeted for avionics, drones, and medical devices.
>>> +
>>> +	  If unsure, say N.
>> Sorry for not noticing this before.  The "If unsure, say $X" should
>> really match the default value.
>>
>> On the other hand, given that we are hiding all these options behind
>> CONFIG_EXPERT, I am not sure that we need "If unsure" clauses.  Anyone
>> who isn't sure shouldn't have turned on CONFIG_EXPERT to start with.
> I was trying to mimic language that the Linux kernel would use for
> EXPERIMENTAL marked items. Given the documentation on the wiki, I think
> marking those three schedulers EXPERIMENTAL is correct.

I concur about their status.

>  Given that, I
> still think that the language saying "If unsure, say N" is correct (the
> thought being, the only people who should be messing with the
> EXPERIMENTAL schedulers are people developing or specifically testing
> them). The *only* reason I marked them default of Y is to keep backwards
> compatibility with the current build.

Also very important.

>
> However, if you would prefer me to remove the "If unsure" language
> completely, I can do that. The text came in before the whole
> CONFIG_EXPERT flag did.

I would suggest dropping it (although you probably want to wait for
opinions from others).  We have already diverged from Linux with regards
to the EXPERT flag; people who are unsure cannot accidentally get here.

~Andrew