Re: [PATCH v3 2/4] mm/page_reporting: Export reporting order as module parameter

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 24, 2021 at 06:55:13AM -0700, Alexander Duyck wrote:
> On Tue, Jun 22, 2021 at 5:34 PM Gavin Shan <gshan@redhat.com> wrote:
> >
> > The macro PAGE_REPORTING_MIN_ORDER is defined as the page reporting
> > threshold. It can't be adjusted at runtime.
> >
> > This introduces a variable (@page_reporting_order) to replace the
> > marcro (PAGE_REPORTING_MIN_ORDER). It's also exported so that the
> > page reporting order can be adjusted at runtime.
> >
> > Suggested-by: David Hildenbrand <david@redhat.com>
> > Signed-off-by: Gavin Shan <gshan@redhat.com>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
> >  mm/page_reporting.c                             | 8 ++++++--
> >  mm/page_reporting.h                             | 5 ++---
> >  3 files changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index cb89dbdedc46..566c4b9af3cd 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -3566,6 +3566,12 @@
> >                         off: turn off poisoning (default)
> >                         on: turn on poisoning
> >
> > +       page_reporting.page_reporting_order=
> > +                       [KNL] Minimal page reporting order
> > +                       Format: <integer>
> > +                       Adjust the minimal page reporting order. The page
> > +                       reporting is disabled when it exceeds (MAX_ORDER-1).
> > +
> 
> Based on the issue found by Stephen I think we may need to tweak this
> a bit. I think we may want to just default this value to MAX_ORDER. We
> can override this value at registration time with the value provided
> either by the reporting device or pageblock_order if prdev->order is
> not set.
> 
> > diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> > index df9c5054e1b4..293a8713ef7c 100644
> > --- a/mm/page_reporting.c
> > +++ b/mm/page_reporting.c
> > @@ -10,6 +10,10 @@
> >  #include "page_reporting.h"
> >  #include "internal.h"
> >
> > +unsigned int page_reporting_order = pageblock_order;
> 
> Rather than setting this to pageblock_order directly you can set this
> to MAX_ORDER which should be constant. Then we can just add some
> checks in page_reporting_register to update it when pageblock_order is
> less than page_reporting_order.
> 
> Then in the next patch you could tweak it so that it will use
> "prdev->order ? : pageblock_order" instead of just pageblock_order.

I like that! Much cleaner ... the patch is in -mm now, I think it's a
good idea to drop it and update to use this idea.

-- 
MST