>
> - TP_printk("page=%p pfn=0x%lx flags=%s",
> - pfn_to_page(__entry->pfn),
> - __entry->pfn,
> - show_reclaim_flags(__entry->reclaim_flags))
> + TP_printk("folio=%p lru=%s",
> + __entry->folio,
> + __print_symbolic(__entry->lru, LRU_NAMES))
> );
> Why is it useful to print out the folio pointer? Printing out the PFN made
> more sense to me.
Tracking a folio pointer gives developers an immediate, unambiguous view of
which memory object is being scanned or reclaimed
and where it lives in the LRU lists, rather than dealing with page frame number.
As you mentioned in patch v1:
https://lore.kernel.org/all/[email protected]/,
the original code chooses to save the pfn, and then forcibly converts it back
to a pointer via pfn_to_page() during printing.
This is an unnecessary indirection that adds code complexity without providing
any extra benefit.
Printing out the PFN surely provides a direct view of the physical address
information, if pfn is needed, just print it by folio_pfn()
as showed below:
TRACE_EVENT(mm_vmscan_write_folio,
TP_PROTO(struct folio *folio),
TP_ARGS(folio),
TP_STRUCT__entry(
__field(struct folio *, folio)
__field(int, lru)
),
TP_fast_assign(
__entry->folio = folio;
__entry->lru = folio_lru_list(folio);
),
TP_printk("folio=%p pfn==0x%lx lru=%s",
__entry->folio,
folio_pfn(__entry->folio),
__print_symbolic(__entry->lru, LRU_NAMES))
);
