The patch titled
Subject: mm: hugetlb: improve the handling of hugetlb allocation failure for freed or in-use hugetlb
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-improve-the-handling-of-hugetlb-allocation-failure-for-freed-or-in-use-hugetlb.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-improve-the-handling-of-hugetlb-allocation-failure-for-freed-or-in-use-hugetlb.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: hugetlb: improve the handling of hugetlb allocation failure for freed or in-use hugetlb
Date: Tue, 6 Feb 2024 11:08:11 +0800
alloc_and_dissolve_hugetlb_folio() preallocates a new hugetlb page before
it takes hugetlb_lock. In 3 out of 4 cases the page is not really used
and therefore the newly allocated page is just freed right away. This is
wasteful and it might cause pre-mature failures in those cases.
Address that by moving the allocation down to the only case (hugetlb page
is really in the free pages pool). We need to drop hugetlb_lock to do so
and therefore need to recheck the page state after regaining it.
The patch is more of a cleanup than an actual fix to an existing problem.
There are no known reports about pre-mature failures.
Link: https://lkml.kernel.org/r/62890fd60b1ecd5bf1cdc476c973f60fe37aa0cb.1707181934.git.baolin.wang@xxxxxxxxxxxxxxxxx
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-improve-the-handling-of-hugetlb-allocation-failure-for-freed-or-in-use-hugetlb
+++ a/mm/hugetlb.c
@@ -3031,21 +3031,9 @@ static int alloc_and_dissolve_hugetlb_fo
{
gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
int nid = folio_nid(old_folio);
- struct folio *new_folio;
+ struct folio *new_folio = NULL;
int ret = 0;
- /*
- * Before dissolving the folio, we need to allocate a new one for the
- * pool to remain stable. Here, we allocate the folio and 'prep' it
- * by doing everything but actually updating counters and adding to
- * the pool. This simplifies and let us do most of the processing
- * under the lock.
- */
- new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL);
- if (!new_folio)
- return -ENOMEM;
- __prep_new_hugetlb_folio(h, new_folio);
-
retry:
spin_lock_irq(&hugetlb_lock);
if (!folio_test_hugetlb(old_folio)) {
@@ -3075,6 +3063,16 @@ retry:
cond_resched();
goto retry;
} else {
+ if (!new_folio) {
+ spin_unlock_irq(&hugetlb_lock);
+ new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid,
+ NULL, NULL);
+ if (!new_folio)
+ return -ENOMEM;
+ __prep_new_hugetlb_folio(h, new_folio);
+ goto retry;
+ }
+
/*
* Ok, old_folio is still a genuine free hugepage. Remove it from
* the freelist and decrease the counters. These will be
@@ -3102,9 +3100,11 @@ retry:
free_new:
spin_unlock_irq(&hugetlb_lock);
- /* Folio has a zero ref count, but needs a ref to be freed */
- folio_ref_unfreeze(new_folio, 1);
- update_and_free_hugetlb_folio(h, new_folio, false);
+ if (new_folio) {
+ /* Folio has a zero ref count, but needs a ref to be freed */
+ folio_ref_unfreeze(new_folio, 1);
+ update_and_free_hugetlb_folio(h, new_folio, false);
+ }
return ret;
}
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
mm-compaction-limit-the-suitable-target-page-order-to-be-less-than-cc-order.patch
mm-compaction-update-the-cc-nr_migratepages-when-allocating-or-freeing-the-freepages.patch
mm-hugetlb-improve-the-handling-of-hugetlb-allocation-failure-for-freed-or-in-use-hugetlb.patch
