The page reference count tracepoints currently look like this:
__entry->pfn = page_to_pfn(page);
__entry->flags = page->flags;
__entry->count = page_ref_count(page);
__entry->mapcount = atomic_read(&page->_mapcount);
__entry->mapping = page->mapping;
__entry->mt = get_pageblock_migratetype(page);
TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d",
Soon, pages will not have a ->mapping, nor a ->mapcount [1]. But they will
still have a refcount, at least for now. put_page() will move out of
line and look something like this:
void put_page(struct page *page)
{
unsigned long memdesc = page->memdesc;
if (memdesc_is_folio(memdesc))
return folio_put(memdesc_folio(memdesc));
BUG_ON(memdesc_is_slab(memdesc));
... handle other memdesc types here ...
if (memdesc_is_compound_head(memdesc))
page = memdesc_head_page(memdesc);
if (put_page_testzero(page))
__put_page(page);
}
What I'm thinking is:
- Define a set of folio_ref_* tracepoints which dump exactly the same info
as page_ref does today
- Remove mapping & mapcount from page_ref_* functions.
Other ideas? I don't use these tracepoints myself; they generate far
too much data to be useful to me.
[1] In case you missed it,
https://lore.kernel.org/linux-mm/Z37pxbkHPbLYnDKn@xxxxxxxxxxxxxxxxxxxx/
