The patch titled
Subject: hugetlb: perform vmemmap restoration on a list of pages
has been added to the -mm mm-unstable branch. Its filename is
hugetlb-perform-vmemmap-restoration-on-a-list-of-pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/hugetlb-perform-vmemmap-restoration-on-a-list-of-pages.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: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: hugetlb: perform vmemmap restoration on a list of pages
Date: Wed, 18 Oct 2023 19:31:06 -0700
The routine update_and_free_pages_bulk already performs vmemmap
restoration on the list of hugetlb pages in a separate step. In
preparation for more functionality to be added in this step, create a new
routine hugetlb_vmemmap_restore_folios() that will restore vmemmap for a
list of folios.
This new routine must provide sufficient feedback about errors and actual
restoration performed so that update_and_free_pages_bulk can perform
optimally.
Special care must be taken when encountering an error from
hugetlb_vmemmap_restore_folios. We want to continue making as much
forward progress as possible. A new routine bulk_vmemmap_restore_error
handles this specific situation.
Link: https://lkml.kernel.org/r/20231019023113.345257-5-mike.kravetz@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Barry Song <21cnbao@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: James Houghton <jthoughton@xxxxxxxxxx>
Cc: Joao Martins <joao.m.martins@xxxxxxxxxx>
Cc: Konrad Dybcio <konradybcio@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Usama Arif <usama.arif@xxxxxxxxxxxxx>
Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 99 +++++++++++++++++++++++++++++------------
mm/hugetlb_vmemmap.c | 38 +++++++++++++++
mm/hugetlb_vmemmap.h | 11 ++++
3 files changed, 120 insertions(+), 28 deletions(-)
--- a/mm/hugetlb.c~hugetlb-perform-vmemmap-restoration-on-a-list-of-pages
+++ a/mm/hugetlb.c
@@ -1859,50 +1859,93 @@ static void update_and_free_hugetlb_foli
schedule_work(&free_hpage_work);
}
-static void update_and_free_pages_bulk(struct hstate *h, struct list_head *list)
+static void bulk_vmemmap_restore_error(struct hstate *h,
+ struct list_head *folio_list,
+ struct list_head *non_hvo_folios)
{
struct folio *folio, *t_folio;
- bool clear_dtor = false;
- /*
- * First allocate required vmemmmap (if necessary) for all folios on
- * list. If vmemmap can not be allocated, we can not free folio to
- * lower level allocator, so add back as hugetlb surplus page.
- * add_hugetlb_folio() removes the page from THIS list.
- * Use clear_dtor to note if vmemmap was successfully allocated for
- * ANY page on the list.
- */
- list_for_each_entry_safe(folio, t_folio, list, lru) {
- if (folio_test_hugetlb_vmemmap_optimized(folio)) {
+ if (!list_empty(non_hvo_folios)) {
+ /*
+ * Free any restored hugetlb pages so that restore of the
+ * entire list can be retried.
+ * The idea is that in the common case of ENOMEM errors freeing
+ * hugetlb pages with vmemmap we will free up memory so that we
+ * can allocate vmemmap for more hugetlb pages.
+ */
+ list_for_each_entry_safe(folio, t_folio, non_hvo_folios, lru) {
+ list_del(&folio->lru);
+ spin_lock_irq(&hugetlb_lock);
+ __clear_hugetlb_destructor(h, folio);
+ spin_unlock_irq(&hugetlb_lock);
+ update_and_free_hugetlb_folio(h, folio, false);
+ cond_resched();
+ }
+ } else {
+ /*
+ * In the case where there are no folios which can be
+ * immediately freed, we loop through the list trying to restore
+ * vmemmap individually in the hope that someone elsewhere may
+ * have done something to cause success (such as freeing some
+ * memory). If unable to restore a hugetlb page, the hugetlb
+ * page is made a surplus page and removed from the list.
+ * If are able to restore vmemmap and free one hugetlb page, we
+ * quit processing the list to retry the bulk operation.
+ */
+ list_for_each_entry_safe(folio, t_folio, folio_list, lru)
if (hugetlb_vmemmap_restore(h, &folio->page)) {
+ list_del(&folio->lru);
spin_lock_irq(&hugetlb_lock);
add_hugetlb_folio(h, folio, true);
spin_unlock_irq(&hugetlb_lock);
- } else
- clear_dtor = true;
- }
+ } else {
+ list_del(&folio->lru);
+ spin_lock_irq(&hugetlb_lock);
+ __clear_hugetlb_destructor(h, folio);
+ spin_unlock_irq(&hugetlb_lock);
+ update_and_free_hugetlb_folio(h, folio, false);
+ cond_resched();
+ break;
+ }
+ }
+}
+
+static void update_and_free_pages_bulk(struct hstate *h,
+ struct list_head *folio_list)
+{
+ long ret;
+ struct folio *folio, *t_folio;
+ LIST_HEAD(non_hvo_folios);
+
+ /*
+ * First allocate required vmemmmap (if necessary) for all folios.
+ * Carefully handle errors and free up any available hugetlb pages
+ * in an effort to make forward progress.
+ */
+retry:
+ ret = hugetlb_vmemmap_restore_folios(h, folio_list, &non_hvo_folios);
+ if (ret < 0) {
+ bulk_vmemmap_restore_error(h, folio_list, &non_hvo_folios);
+ goto retry;
}
/*
- * If vmemmmap allocation was performed on any folio above, take lock
- * to clear destructor of all folios on list. This avoids the need to
- * lock/unlock for each individual folio.
- * The assumption is vmemmap allocation was performed on all or none
- * of the folios on the list. This is true expect in VERY rare cases.
+ * At this point, list should be empty, ret should be >= 0 and there
+ * should only be pages on the non_hvo_folios list.
+ * Do note that the non_hvo_folios list could be empty.
+ * Without HVO enabled, ret will be 0 and there is no need to call
+ * __clear_hugetlb_destructor as this was done previously.
*/
- if (clear_dtor) {
+ VM_WARN_ON(!list_empty(folio_list));
+ VM_WARN_ON(ret < 0);
+ if (!list_empty(&non_hvo_folios) && ret) {
spin_lock_irq(&hugetlb_lock);
- list_for_each_entry(folio, list, lru)
+ list_for_each_entry(folio, &non_hvo_folios, lru)
__clear_hugetlb_destructor(h, folio);
spin_unlock_irq(&hugetlb_lock);
}
- /*
- * Free folios back to low level allocators. vmemmap and destructors
- * were taken care of above, so update_and_free_hugetlb_folio will
- * not need to take hugetlb lock.
- */
- list_for_each_entry_safe(folio, t_folio, list, lru) {
+ list_for_each_entry_safe(folio, t_folio, &non_hvo_folios, lru) {
update_and_free_hugetlb_folio(h, folio, false);
cond_resched();
}
--- a/mm/hugetlb_vmemmap.c~hugetlb-perform-vmemmap-restoration-on-a-list-of-pages
+++ a/mm/hugetlb_vmemmap.c
@@ -480,6 +480,44 @@ int hugetlb_vmemmap_restore(const struct
return ret;
}
+/**
+ * hugetlb_vmemmap_restore_folios - restore vmemmap for every folio on the list.
+ * @h: hstate.
+ * @folio_list: list of folios.
+ * @non_hvo_folios: Output list of folios for which vmemmap exists.
+ *
+ * Return: number of folios for which vmemmap was restored, or an error code
+ * if an error was encountered restoring vmemmap for a folio.
+ * Folios that have vmemmap are moved to the non_hvo_folios
+ * list. Processing of entries stops when the first error is
+ * encountered. The folio that experienced the error and all
+ * non-processed folios will remain on folio_list.
+ */
+long hugetlb_vmemmap_restore_folios(const struct hstate *h,
+ struct list_head *folio_list,
+ struct list_head *non_hvo_folios)
+{
+ struct folio *folio, *t_folio;
+ long restored = 0;
+ long ret = 0;
+
+ list_for_each_entry_safe(folio, t_folio, folio_list, lru) {
+ if (folio_test_hugetlb_vmemmap_optimized(folio)) {
+ ret = hugetlb_vmemmap_restore(h, &folio->page);
+ if (ret)
+ break;
+ restored++;
+ }
+
+ /* Add non-optimized folios to output list */
+ list_move(&folio->lru, non_hvo_folios);
+ }
+
+ if (!ret)
+ ret = restored;
+ return ret;
+}
+
/* Return true iff a HugeTLB whose vmemmap should and can be optimized. */
static bool vmemmap_should_optimize(const struct hstate *h, const struct page *head)
{
--- a/mm/hugetlb_vmemmap.h~hugetlb-perform-vmemmap-restoration-on-a-list-of-pages
+++ a/mm/hugetlb_vmemmap.h
@@ -19,6 +19,9 @@
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
+long hugetlb_vmemmap_restore_folios(const struct hstate *h,
+ struct list_head *folio_list,
+ struct list_head *non_hvo_folios);
void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);
void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list);
@@ -45,6 +48,14 @@ static inline int hugetlb_vmemmap_restor
return 0;
}
+static long hugetlb_vmemmap_restore_folios(const struct hstate *h,
+ struct list_head *folio_list,
+ struct list_head *non_hvo_folios)
+{
+ list_splice_init(folio_list, non_hvo_folios);
+ return 0;
+}
+
static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
{
}
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
hugetlb-optimize-update_and_free_pages_bulk-to-avoid-lock-cycles.patch
hugetlb-restructure-pool-allocations.patch
hugetlb-perform-vmemmap-optimization-on-a-list-of-pages.patch
hugetlb-perform-vmemmap-restoration-on-a-list-of-pages.patch
hugetlb-batch-freeing-of-vmemmap-pages.patch
hugetlb-batch-tlb-flushes-when-restoring-vmemmap.patch
