Re: [PATCH v2] Documentation/cgroup-v2: Update memory.{stat,numa_stat} description to reflect possible units

[Jonathan Corbet <corbet@lwn.net>]

Li Zhijian <lizhijian@fujitsu.com> writes:

> The description of the memory.{stat,numa_stat} file has been updated to
> clarify that the output values can be in bytes or pages.
> This change ensures that users are aware that the unit of measurement for
> memory values can vary and should be verified by consulting the memory.stat
>
> It's known that
> workingset_*, pg* are counted in pages
>
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>a
> ---
> V2: updated the document as suggestion from Michal
>     updated subject and commit log
> ---
>  Documentation/admin-guide/cgroup-v2.rst | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 315ede811c9d..0a43be0c32d1 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -1427,7 +1427,7 @@ The following nested keys are defined.
>  	types of memory, type-specific details, and other information
>  	on the state and past events of the memory management system.
>  
> -	All memory amounts are in bytes.
> +	All memory amounts are in bytes unless said otherwise.
>  
>  	The entries are ordered to be human readable, and new entries
>  	can show up in the middle. Don't rely on items remaining in a
> @@ -1673,11 +1673,12 @@ The following nested keys are defined.
>  	application performance by combining this information with the
>  	application's CPU allocation.
>  
> -	All memory amounts are in bytes.
> -
>  	The output format of memory.numa_stat is::
>  
> -	  type N0=<bytes in node 0> N1=<bytes in node 1> ...
> +	  type N0=<value for node 0> N1=<value for node 1> ...
> +
> +        The 'value' can be in bytes or pages, depending on the specific
> +        type of memory. To determine the unit, refer to the memory.stat.

This seems like useful information - but can we really not give better
guidance to our readers on how to interpret this value?  What in "the
memory.stat" will tell them which units are in use?

(Even better, could we fix the code to always return the same units
without breaking something somewhere?)

Thanks,

jon