The patch titled
Subject: hugetlb: call update_and_free_page without hugetlb_lock
has been added to the -mm tree. Its filename is
hugetlb-call-update_and_free_page-without-hugetlb_lock.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-call-update_and_free_page-without-hugetlb_lock.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-call-update_and_free_page-without-hugetlb_lock.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: hugetlb: call update_and_free_page without hugetlb_lock
With the introduction of remove_hugetlb_page(), there is no need for
update_and_free_page to hold the hugetlb lock. Change all callers to drop
the lock before calling.
With additional code modifications, this will allow loops which decrease
the huge page pool to drop the hugetlb_lock with each page to reduce long
hold times.
The ugly unlock/lock cycle in free_pool_huge_page will be removed in a
subsequent patch which restructures free_pool_huge_page.
Link: https://lkml.kernel.org/r/20210331034148.112624-6-mike.kravetz@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
--- a/mm/hugetlb.c~hugetlb-call-update_and_free_page-without-hugetlb_lock
+++ a/mm/hugetlb.c
@@ -1452,16 +1452,18 @@ static void __free_huge_page(struct page
if (HPageTemporary(page)) {
remove_hugetlb_page(h, page, false);
+ spin_unlock(&hugetlb_lock);
update_and_free_page(h, page);
} else if (h->surplus_huge_pages_node[nid]) {
/* remove the page from active list */
remove_hugetlb_page(h, page, true);
+ spin_unlock(&hugetlb_lock);
update_and_free_page(h, page);
} else {
arch_clear_hugepage_flags(page);
enqueue_huge_page(h, page);
+ spin_unlock(&hugetlb_lock);
}
- spin_unlock(&hugetlb_lock);
}
/*
@@ -1742,7 +1744,13 @@ static int free_pool_huge_page(struct hs
list_entry(h->hugepage_freelists[node].next,
struct page, lru);
remove_hugetlb_page(h, page, acct_surplus);
+ /*
+ * unlock/lock around update_and_free_page is temporary
+ * and will be removed with subsequent patch.
+ */
+ spin_unlock(&hugetlb_lock);
update_and_free_page(h, page);
+ spin_lock(&hugetlb_lock);
ret = 1;
break;
}
@@ -1811,8 +1819,9 @@ retry:
}
remove_hugetlb_page(h, page, false);
h->max_huge_pages--;
+ spin_unlock(&hugetlb_lock);
update_and_free_page(h, head);
- rc = 0;
+ return 0;
}
out:
spin_unlock(&hugetlb_lock);
@@ -2675,22 +2684,34 @@ static void try_to_free_low(struct hstat
nodemask_t *nodes_allowed)
{
int i;
+ struct page *page, *next;
+ LIST_HEAD(page_list);
if (hstate_is_gigantic(h))
return;
+ /*
+ * Collect pages to be freed on a list, and free after dropping lock
+ */
for_each_node_mask(i, *nodes_allowed) {
- struct page *page, *next;
struct list_head *freel = &h->hugepage_freelists[i];
list_for_each_entry_safe(page, next, freel, lru) {
if (count >= h->nr_huge_pages)
- return;
+ goto out;
if (PageHighMem(page))
continue;
remove_hugetlb_page(h, page, false);
- update_and_free_page(h, page);
+ list_add(&page->lru, &page_list);
}
}
+
+out:
+ spin_unlock(&hugetlb_lock);
+ list_for_each_entry_safe(page, next, &page_list, lru) {
+ update_and_free_page(h, page);
+ cond_resched();
+ }
+ spin_lock(&hugetlb_lock);
}
#else
static inline void try_to_free_low(struct hstate *h, unsigned long count,
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
mm-cma-change-cma-mutex-to-irq-safe-spinlock.patch
hugetlb-no-need-to-drop-hugetlb_lock-to-call-cma_release.patch
hugetlb-add-per-hstate-mutex-to-synchronize-user-adjustments.patch
hugetlb-create-remove_hugetlb_page-to-separate-functionality.patch
hugetlb-call-update_and_free_page-without-hugetlb_lock.patch
hugetlb-change-free_pool_huge_page-to-remove_pool_huge_page.patch
hugetlb-make-free_huge_page-irq-safe.patch
hugetlb-add-lockdep_assert_held-calls-for-hugetlb_lock.patch
