Re: [PATCH] sched: print information about scheduler granularity

[Sergey Dyasli <sergey.dyasli@citrix.com>]

On 16/04/2020 10:25, Jürgen Groß wrote:
> On 16.04.20 11:20, Sergey Dyasli wrote:
>> On 16/04/2020 09:57, Jürgen Groß wrote:
>>> On 16.04.20 10:33, Sergey Dyasli wrote:
>>>> Currently it might be not obvious which scheduling mode is being used
>>>> by the scheduler. Alleviate this by printing additional information
>>>> about the selected granularity. Messages now look like these:
>>>>
>>>> 1. boot
>>>> (XEN) [00089808f0ea7496] Using scheduler: SMP Credit Scheduler (credit) in core-scheduling mode
>>>>
>>>> 2. xl debug-keys r
>>>> (XEN) [   45.914314] Scheduler: SMP Credit Scheduler (credit) in 2-way core-scheduling mode
>>>>
>>>> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
>>>
>>> Hmm, do we need that?
>>>
>>> The xen commandline ins part of the boot messages and is contained
>>> in the "xl info" output.
>>
>> It's true that you can see "sched-gran=core" in "xl info" output. But that's
>> just the switch - not the end result. A user might want to verify that he did
>> everything correctly and core-scheduling mode has indeed been enabled.
> 
> I'm planning to add this information in the pending hypfs (per cpupool).

hypfs is certainly nice, but I doubt it'll be available for Xen 4.13.

> I'm not opposed to your patch, but as soon as we have per-cpupool
> granularity it should be reverted again.

"xl debug-keys r" already prints the granularity information per cpupool.
It's just opt_sched_granularity is currently a single global variable. Once
per-cpupool granularity is implemented, sched_gran_str() should simply gain
granularity as a parameter.

--
Thanks,
Sergey