Re: [PATCH v2 1/4] mm: free zapped tail pages when splitting isolated thp

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 07.08.24 15:46, Usama Arif wrote:
From: Yu Zhao <yuzhao@xxxxxxxxxx>

If a tail page has only two references left, one inherited from the
isolation of its head and the other from lru_add_page_tail() which we
are about to drop, it means this tail page was concurrently zapped.
Then we can safely free it and save page reclaim or migration the
trouble of trying it.

Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Tested-by: Shuang Zhai <zhais@xxxxxxxxxx>
Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
---
  mm/huge_memory.c | 27 +++++++++++++++++++++++++++
  1 file changed, 27 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 0167dc27e365..35c1089d8d61 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2923,7 +2923,9 @@ static void __split_huge_page(struct page *page, struct list_head *list,
  	unsigned int new_nr = 1 << new_order;
  	int order = folio_order(folio);
  	unsigned int nr = 1 << order;
+	struct folio_batch free_folios;
+ folio_batch_init(&free_folios);
  	/* complete memcg works before add pages to LRU */
  	split_page_memcg(head, order, new_order);
@@ -3007,6 +3009,26 @@ static void __split_huge_page(struct page *page, struct list_head *list,
  		if (subpage == page)
  			continue;
  		folio_unlock(new_folio);
+		/*
+		 * If a folio has only two references left, one inherited
+		 * from the isolation of its head and the other from
+		 * lru_add_page_tail() which we are about to drop, it means this
+		 * folio was concurrently zapped. Then we can safely free it
+		 * and save page reclaim or migration the trouble of trying it.
+		 */
+		if (list && page_ref_freeze(subpage, 2)) {
+			VM_WARN_ON_ONCE_FOLIO(folio_test_lru(new_folio), new_folio);
+			VM_WARN_ON_ONCE_FOLIO(folio_test_large(new_folio), new_folio);
+			VM_WARN_ON_ONCE_FOLIO(folio_mapped(new_folio), new_folio);
+
+			folio_clear_active(new_folio);
+			folio_clear_unevictable(new_folio);
+			if (folio_batch_add(&free_folios, folio) == 0) {

nit:  "!folio_batch_add(&free_folios, folio)"

Nothing else jumped at me.

--
Cheers,

David / dhildenb





[Index of Archives]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux