Re: [RFC PATCH 11/15] mm/page_reporting: report pages at section size instead of MAX_ORDER.

[David Hildenbrand]

On 05.08.21 21:02, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
>
> page_reporting_order was set to MAX_ORDER, which is always smaller than
> a memory section size. An upcoming change will make MAX_ORDER larger
> than a memory section size. Set page_reporting_order to
> PFN_SECTION_SHIFT to match existing size assumption.
>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>   mm/page_reporting.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> index 382958eef8a9..dc4a2d699862 100644
> --- a/mm/page_reporting.c
> +++ b/mm/page_reporting.c
> @@ -11,7 +11,8 @@
>   #include "page_reporting.h"
>   #include "internal.h"
>   
> -unsigned int page_reporting_order = MAX_ORDER;
> +/* Set page_reporting_order at section size */
> +unsigned int page_reporting_order = PFN_SECTION_SHIFT;
>   module_param(page_reporting_order, uint, 0644);
>   MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
>   

If you look closely, this is only a placeholder and will get overwritten 
in page_reporting_register(). I don't recall why we have the module 
parameter at all. Most probably, to adjust the reporting order after we 
already registered a user. Can't we just initialize that to 0 ?

--
Thanks,

David / dhildenb