> So you are going to need a lot more explanation for this. Page
> reporting already had the concept of batching as you could only scan
> once every 2 seconds as I recall. Thus the "PAGE_REPORTING_DELAY". The
> change you are making doesn't make any sense without additional
> context.
The reason for adding a batch is mainly for page prezero, I just want to make it
configurable to control the 'cache pollution', for that case, the
reporting thread
should not be woken up too frequently.
> > ---
> > mm/page_reporting.c | 1 +
> > mm/page_reporting.h | 12 ++++++++++--
> > 2 files changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> > index cd8e13d41df4..694df981ddd2 100644
> > --- a/mm/page_reporting.c
> > +++ b/mm/page_reporting.c
> > @@ -12,6 +12,7 @@
> >
> > #define PAGE_REPORTING_DELAY (2 * HZ)
> > static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
> > +unsigned long page_report_batch_size __read_mostly = 16 * 1024 * 1024UL;
> >
> > enum {
> > PAGE_REPORTING_IDLE = 0,
> > diff --git a/mm/page_reporting.h b/mm/page_reporting.h
> > index 2c385dd4ddbd..b8fb3bbb345f 100644
> > --- a/mm/page_reporting.h
> > +++ b/mm/page_reporting.h
> > @@ -12,6 +12,8 @@
> >
> > #define PAGE_REPORTING_MIN_ORDER pageblock_order
> >
> > +extern unsigned long page_report_batch_size;
> > +
> > #ifdef CONFIG_PAGE_REPORTING
> > DECLARE_STATIC_KEY_FALSE(page_reporting_enabled);
> > void __page_reporting_notify(void);
> > @@ -33,6 +35,8 @@ static inline bool page_reported(struct page *page)
> > */
> > static inline void page_reporting_notify_free(unsigned int order)
> > {
> > + static long batch_size;
> > +
>
> I'm not sure this makes a tone of sense to place the value in an
> inline function. It might make more sense to put this new code in
> __page_reporting_notify so that all callers would be referring to the
> same batch_size value and you don't have to bother with the export of
> the page_report_batch_size value.
you are right, will change.
> > /* Called from hot path in __free_one_page() */
> > if (!static_branch_unlikely(&page_reporting_enabled))
> > return;
> > @@ -41,8 +45,12 @@ static inline void page_reporting_notify_free(unsigned int order)
> > if (order < PAGE_REPORTING_MIN_ORDER)
> > return;
> >
> > - /* This will add a few cycles, but should be called infrequently */
> > - __page_reporting_notify();
> > + batch_size += (1 << order) << PAGE_SHIFT;
> > + if (batch_size >= page_report_batch_size) {
> > + batch_size = 0;
>
> I would probably run this in the opposite direction. Rather than
> running batch_size to zero I would look at adding a "batch_remaining"
> and then when it is < 0 you could then reset it back to
> page_report_batch_size. Doing that you only have to read one variable
> most of the time instead of doing a comparison against two.
You are right again.
Thanks
Liang
