Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT

On Fri 12-07-19 09:58:09, Johannes Weiner wrote:
[...]

quoted

@@ -423,6 +445,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
 
 		VM_BUG_ON_PAGE(PageTransCompound(page), page);
 
+		if (pageout) {
+			if (isolate_lru_page(page))
+				continue;
+			list_add(&page->lru, &page_list);
+		}
+
 		if (pte_young(ptent)) {
 			ptent = ptep_get_and_clear_full(mm, addr, pte,
 							tlb->fullmm);

One thought on the ordering here.

When LRU isolation fails, it would still make sense to clear the young
bit: we cannot reclaim the page as we wanted to, but the user still
provided a clear hint that the page is cold and she won't be touching
it for a while. MADV_PAGEOUT is basically MADV_COLD + try_to_reclaim.
So IMO isolation should go to the end next to deactivate_page().

Make sense to me

-- 
Michal Hocko
SUSE Labs