Bharata B Rao <bharata@xxxxxxx> writes:
[snip]
> @@ -1750,25 +1753,20 @@ static bool pgdat_free_space_enough(struct pglist_data *pgdat)
> }
>
> /*
> - * For memory tiering mode, when page tables are scanned, the scan
> - * time will be recorded in struct page in addition to make page
> - * PROT_NONE for slow memory page. So when the page is accessed, in
> - * hint page fault handler, the hint page fault latency is calculated
> - * via,
> + * For memory tiering mode, when page tables are scanned, the current
> + * hint fault count will be recorded in struct page in addition to
> + * make page PROT_NONE for slow memory page. So when the page is
> + * accessed, in hint page fault handler, the hint page fault latency is
> + * calculated via,
> *
> - * hint page fault latency = hint page fault time - scan time
> + * hint page fault latency = current hint fault count - fault count at scan time
> *
> * The smaller the hint page fault latency, the higher the possibility
> * for the page to be hot.
> */
> -static int numa_hint_fault_latency(struct folio *folio)
> +static inline int numa_hint_fault_latency(struct folio *folio, int count)
> {
> - int last_time, time;
> -
> - time = jiffies_to_msecs(jiffies);
> - last_time = folio_xchg_access_time(folio, time);
> -
> - return (time - last_time) & PAGE_ACCESS_TIME_MASK;
> + return count - folio_xchg_fault_count(folio, count);
> }
I found count is task->mm->hint_faults. That is a process wide
counting. How do you connect the hotness of a folio with the count of
hint page fault in the process? How do you compare the hotness of
folios among different processes?
> /*
> @@ -1794,35 +1792,6 @@ static bool numa_promotion_rate_limit(struct pglist_data *pgdat,
> return false;
> }
>
--
Best Regards,
Huang, Ying
