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

[Jonathan Creekmore <jonathan.creekmore@xxxxxxxxx>]

Andrew Cooper writes:

> 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.

OK, if I haven't heard anything from any others by the time I send out
my v5 on Monday with the other items you caught, then I will go ahead
and remove the language.

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