Re: [PATCH] mm/vmstat: Add events for PMD based THP migration without split

[Daniel Jordan]

On Wed, Jun 03, 2020 at 10:06:31AM +0530, Anshuman Khandual wrote:
> Does this look okay and sufficient ?
> 
> --- a/Documentation/vm/page_migration.rst
> +++ b/Documentation/vm/page_migration.rst
> @@ -253,5 +253,20 @@ which are function pointers of struct address_space_operations.
>       PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag
>       for own purpose.
>  
> +Quantifying Migration
> +=====================
> +Following events can be used to quantify page migration.
> +
> +- PGMIGRATE_SUCCESS
> +- PGMIGRATE_FAIL
> +- THP_MIGRATION_SUCCESS
> +- THP_MIGRATION_FAILURE
> +
> +THP_MIGRATION_FAILURE in particular represents an event when a THP could not be
> +migrated as a single entity following an allocation failure and ended up getting
> +split into constituent normal pages before being retried. This event, along with
> +PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in quantifying and analyzing THP
> +migration events including both success and failure cases.

Looks great!

> Sure, will update the commit message accordingly.

Thanks.  Hopefully these will help someone in the future.