archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <>
Subject: [patch 05/13] mm/page_alloc: fix counting of free pages after take off from buddy
Date: Fri, 04 Jun 2021 20:01:21 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

From: Ding Hui <>
Subject: mm/page_alloc: fix counting of free pages after take off from buddy

Recently we found that there is a lot MemFree left in /proc/meminfo after
do a lot of pages soft offline, it's not quite correct.

Before Oscar rework soft offline for free pages [1], if we soft offline
free pages, these pages are left in buddy with HWPoison flag, and
NR_FREE_PAGES is not updated immediately.  So the difference between
NR_FREE_PAGES and real number of available free pages is also even big at
the beginning.

However, with the workload running, when we catch HWPoison page in any
alloc functions subsequently, we will remove it from buddy, meanwhile
update the NR_FREE_PAGES and try again, so the NR_FREE_PAGES will get more
and more closer to the real number of available free pages.  (regardless
of unpoison_memory())

Now, 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, and there is no chance to be updated later.

Do update in take_page_off_buddy() like rmqueue() does, but avoid double
counting if some one already set_migratetype_isolate() on the page.

[1]: commit 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages")

Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages")
Signed-off-by: Ding Hui <>
Suggested-by: Naoya Horiguchi <>
Reviewed-by: Oscar Salvador <>
Acked-by: David Hildenbrand <>
Acked-by: Naoya Horiguchi <>
Cc: <>
Signed-off-by: Andrew Morton <>

 mm/page_alloc.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/page_alloc.c~mm-page_alloc-fix-counting-of-free-pages-after-take-off-from-buddy
+++ a/mm/page_alloc.c
@@ -9158,6 +9158,8 @@ bool take_page_off_buddy(struct page *pa
 			del_page_from_free_list(page_head, zone, page_order);
 			break_down_buddy_pages(zone, page_head, page, 0,
 						page_order, migratetype);
+			if (!is_migrate_isolate(migratetype))
+				__mod_zone_freepage_state(zone, -1, migratetype);
 			ret = true;

  parent reply	other threads:[~2021-06-05  6:37 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-05  3:00 incoming Andrew Morton
2021-06-05  3:01 ` [patch 01/13] Revert "MIPS: make userspace mapping young by default" Andrew Morton
2021-06-05  3:01 ` [patch 02/13] kfence: use TASK_IDLE when awaiting allocation Andrew Morton
2021-06-05  3:01 ` [patch 03/13] pid: take a reference when initializing `cad_pid` Andrew Morton
2021-06-05  3:01 ` [patch 04/13] mm/debug_vm_pgtable: fix alignment for pmd/pud_advanced_tests() Andrew Morton
2021-06-05  3:01 ` Andrew Morton [this message]
2021-06-05  3:01 ` [patch 06/13] drivers/base/memory: fix trying offlining memory blocks with memory holes on aarch64 Andrew Morton
2021-06-05  3:01 ` [patch 07/13] hugetlb: pass head page to remove_hugetlb_page() Andrew Morton
2021-06-05  3:01 ` [patch 08/13] proc: add .gitignore for proc-subset-pid selftest Andrew Morton
2021-06-05  3:01 ` [patch 09/13] mm/kasan/init.c: fix doc warning Andrew Morton
2021-06-05  3:01 ` [patch 10/13] mm, hugetlb: fix simple resv_huge_pages underflow on UFFDIO_COPY Andrew Morton
2021-06-05  3:01 ` [patch 11/13] lib: crc64: fix kernel-doc warning Andrew Morton
2021-06-05  3:01 ` [patch 12/13] ocfs2: fix data corruption by fallocate Andrew Morton
2021-06-05  3:01 ` [patch 13/13] mailmap: use private address for Michel Lespinasse Andrew Morton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [patch 05/13] mm/page_alloc: fix counting of free pages after take off from buddy' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox