Re: [PATCH v3] qapi/qom: Memory backend property prealloc-threads doc fix

[Markus Armbruster]

Gavin Shan <gshan@redhat.com> writes:

> Hi Zhenyu,
>
> On 11/11/22 11:05 AM, Zhenyu Zhang wrote:
>> Commit ffac16fab3 "hostmem: introduce "prealloc-threads" property"
>> (v5.0.0) changed the default number of threads from number of CPUs
>> to 1.  This was deemed a regression, and fixed in commit f8d426a685
>> "hostmem: default the amount of prealloc-threads to smp-cpus".
>> Except the documentation remained unchanged.  Update it now.
>> Signed-off-by: Zhenyu Zhang <zhenyzha@redhat.com>
>> ---
>> v3: Covers historical descriptions                  (Markus)
>> v2: The property is changed to smp-cpus since 5.0   (Phild)
>> ---
>>   qapi/qom.json | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>
> With the following comments addressed:
>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
>
> ---
>
> Please consider amending the commit log to something like below.
>
> The default "prealloc-threads" value is set to 1 when the property is
> added by commit ffac16fab33b ("hostmem: introduce "prealloc-threads"
> property") in v5.0.0. The default value is conflicting with the sugar
> property as the value provided by the sugar property is number of CPUs.

What is the sugar property?  Can you explain the conflict in a bit more
detail?

> The conflict has been fixed by commit f8d426a6852c ("hostmem: default
> the amount of prealloc-threads to smp-cpus"). However, 'qapi/qom.json'
> was missed to be updated accordingly in the commit.
>
> Update 'qapi/qom.json' to reflect the change in commit f8d426a6852c.
>
> Signed-off-by: Zhenyu Zhang <zhenyzha@redhat.com>
>
> When a specific commit is mentioned in the commit log, we usually have
> fixed format like below.
>
> commit ffac16fab33b ("hostmem: introduce "prealloc-threads" property")
> commit f8d426a6852c ("hostmem: default the amount of prealloc-threads to 
> smp-cpus")

This is certainly a common format, but the other one is also in use.

>> diff --git a/qapi/qom.json b/qapi/qom.json
>> index 30e76653ad..dfd89bc6d4 100644
>> --- a/qapi/qom.json
>> +++ b/qapi/qom.json
>> @@ -576,7 +576,7 @@
>>   #
>>   # @prealloc: if true, preallocate memory (default: false)
>>   #
>> -# @prealloc-threads: number of CPU threads to use for prealloc (default: 1)
>> +# @prealloc-threads: number of CPU threads to use for prealloc (default: 
>> number of CPUs) (since 5.0)
>>   #
>>   # @prealloc-context: thread context to use for creation of preallocation 
>> threads
>>   #                    (default: none) (since 7.2)
>> 
>
> The line seems exceeding 80 characters. It'd better to limit each line in 75 
> characters.
> So you probably need:
>
>     # @prealloc-threads: number of CPU threads to use for prealloc (default: 
> number of CPUs)
>     #                    (since 5.0)

Still exceeds :)

I suggested

      # @prealloc-threads: number of CPU threads to use for prealloc
      #                    (default: number of CPUs) (since 5.0)