Re: [PATCH v2] mm/page_alloc: fix counting of free pages after take off from buddy
From: HORIGUCHI NAOYA (堀口 直也) <hidden>
Date: 2021-05-25 08:32:37
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On Sat, May 08, 2021 at 11:55:33AM +0800, Ding Hui wrote:
quoted hunk ↗ jump to hunk
Recently we found there is a lot MemFree left in /proc/meminfo after do a lot of pages soft offline. I think it's incorrect since NR_FREE_PAGES should not contain HWPoison pages. For offline free pages, after a successful call take_page_off_buddy(), the page is no longer belong to buddy allocator, and will not be used any more, but we missed accounting NR_FREE_PAGES in this situation. Do update like rmqueue() does. Signed-off-by: Ding Hui <redacted> --- V2: use __mod_zone_freepage_state instead of __mod_zone_page_state mm/page_alloc.c | 1 + 1 file changed, 1 insertion(+)diff --git a/mm/page_alloc.c b/mm/page_alloc.c index cfc72873961d..e124a615303b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -8947,6 +8947,7 @@ bool take_page_off_buddy(struct page *page) del_page_from_free_list(page_head, zone, page_order); break_down_buddy_pages(zone, page_head, page, 0, page_order, migratetype); + __mod_zone_freepage_state(zone, -1, migratetype);
Page offline code (see set_migratetype_isolate()) seems to handle NR_FREE_PAGES counter in its own way, so I think that it's more correct to call __mod_zone_freepage_state() only when is_migrate_isolate(migratetype)) is false. Otherwise, the patch looks good to me. Thanks, Naoya Horiguchi
ret = true; break; } -- 2.17.1