[PATCH] docs: fix documentation about default scheduler

[PATCH] docs: fix documentation about default scheduler

[Roger Pau Monne]

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.
 
 Choose the default scheduler.
 
-- 
2.29.0

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

[George Dunlap]

> 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.

I’d rather say:

—>8

= credit | credit2 …

Default: sched=credit2

NB that default scheduler and schedulers available can be modified via Kconfig.

8<----

 -George

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

[Andrew Cooper]

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.

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.

~Andrew

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

[George Dunlap]

> 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

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

[Roger Pau Monné]

On Wed, Nov 11, 2020 at 12:24:50PM +0100, George Dunlap wrote:
> 
> 
> > 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.

I'm happy to send an updated version, but would like to have some
agreement before doing so. Is the text below acceptable to everyone?

### sched
> `= credit | credit2 | arinc653 | rtds | null`

> Default: `sched=credit2`

Choose the default scheduler. Note the default scheduler is selectable via
Kconfig and depends on enabled schedulers. Check
`CONFIG_SCHED_{scheduler_name}_DEFAULT` when you building Xen to adjust the
default scheduler.

Roger.

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

[Jürgen Groß]

[-- Attachment #1.1.1: Type: text/plain, Size: 3159 bytes --]

On 11.11.20 12:37, Roger Pau Monné wrote:
> On Wed, Nov 11, 2020 at 12:24:50PM +0100, George Dunlap wrote:
>>
>>
>>> 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.
> 
> I'm happy to send an updated version, but would like to have some
> agreement before doing so. Is the text below acceptable to everyone?
> 
> ### sched
>> `= credit | credit2 | arinc653 | rtds | null`
> 
>> Default: `sched=credit2`
> 
> Choose the default scheduler. Note the default scheduler is selectable via
> Kconfig and depends on enabled schedulers. Check

... CONFIG_SCHED_DEFAULT to see which scheduler is the default.

CONFIG_SCHED_{scheduler_name} specify which schedulers are available.


Juergen

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

[Roger Pau Monné]

On Wed, Nov 11, 2020 at 12:45:38PM +0100, Jürgen Groß wrote:
> On 11.11.20 12:37, Roger Pau Monné wrote:
> > On Wed, Nov 11, 2020 at 12:24:50PM +0100, George Dunlap wrote:
> > > 
> > > 
> > > > 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.
> > 
> > I'm happy to send an updated version, but would like to have some
> > agreement before doing so. Is the text below acceptable to everyone?
> > 
> > ### sched
> > > `= credit | credit2 | arinc653 | rtds | null`
> > 
> > > Default: `sched=credit2`
> > 
> > Choose the default scheduler. Note the default scheduler is selectable via
> > Kconfig and depends on enabled schedulers. Check
> 
> ... CONFIG_SCHED_DEFAULT to see which scheduler is the default.
> 
> CONFIG_SCHED_{scheduler_name} specify which schedulers are available.

Hm, that's weird. When I hit help in menuconfig for the default
scheduler selection it reports the option is named
SCHED_{name}_DEFAULT. Will change it.

Roger.