On Mon, Aug 9, 2021 at 8:08 AM Zi Yan <ziy@xxxxxxxxxx> wrote: > > On 9 Aug 2021, at 10:12, Alexander Duyck wrote: > > > On Mon, Aug 9, 2021 at 12:25 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > >> > >> 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 ? > > > > Yeah, it is pretty much there for debugging in the event that we are > > on an architecture that is misconfigured. > > MAX_ORDER is changed to a boot time variable in Patch 15, thus cannot be used > for page_reporting_order initialization after that. > > Thanks for David’s explanation. I will initialize page_reporting_order to 0 > and fix the commit message. Rather than 0 it might be better to use (unsigned)-1 as that would prevent page reporting from being able to run until the value is overwritten.
