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

From: David Hildenbrand
Date: Mon Aug 09 2021 - 03:25:46 EST


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