Re: [PATCH] docs: fix documentation about default scheduler

[George Dunlap <George.Dunlap@citrix.com>]

> On Nov 11, 2020, at 11:10 AM, Andrew Cooper <Andrew.Cooper3@citrix.com> wrote:
> 
> On 11/11/2020 10:12, George Dunlap wrote:
>> 
>>> On Nov 10, 2020, at 6:51 PM, Roger Pau Monne <roger.pau@citrix.com> wrote:
>>> 
>>> Fix the command line document to account for the default scheduler not
>>> being credit anymore likely, and the fact that it's selectable from
>>> Kconfig and thus different builds could end up with different default
>>> schedulers.
>>> 
>>> Fixes: dafd936dddbd ('Make credit2 the default scheduler')
>>> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
>>> ---
>>> Changes since v1:
>>> - Point that the default scheduler is being selected by Kconfig,
>>>  don't mention the default Kconfig selection.
>>> ---
>>> docs/misc/xen-command-line.pandoc | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>> 
>>> diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
>>> index 4ae9391fcd..eb1db25f92 100644
>>> --- a/docs/misc/xen-command-line.pandoc
>>> +++ b/docs/misc/xen-command-line.pandoc
>>> @@ -1876,7 +1876,7 @@ with read and write permissions.
>>> ### sched
>>>> `= credit | credit2 | arinc653 | rtds | null`
>>> -> Default: `sched=credit`
>>> +> Default: selectable via Kconfig.  Depends on enabled schedulers.
>> Sorry for not weighing in earlier; but this basically makes this documentation useless.
> 
> No.  It is the only half useable version, by being the only version
> which isn't misleading.

The version in this patch essentially says “This has some options, it also has a default, but we’re not going to tell you any of them, nor what your default most likely is.  Go read KConfig to find out.”  This is is completely useless to the person trying to figure out what the default is and what potential alternate values they can put here.

The vast majority of people who search for this on the internet will have that list of options, and have credit2=default.  As long as we tell them that a local configuration can override the available options and the default, people are smart enough to figure out what their system is doing.

> It would however be far better to name the CONFIG_ variable (we do
> elsewhere in this doc) in question so people can actually figure out
> what they've got in front of them.

Something like that would be even better, if Roger (or someone) wants to write it up.

 -George