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

[Alexander Duyck]

On Thu, Aug 5, 2021 at 12:04 PM Zi Yan <zi.yan@xxxxxxxx> 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");

The MAX_ORDER assumption is correct. The general idea with this being
set to MAX_ORDER is that the processing is from page_reporting_order
to MAX_ORDER. So with it set to MAX_ORDER then page reporting is
disabled.