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Message-ID: <efeb775e-57f1-5f5c-a23a-9a4309948995@huawei.com>
Date: Tue, 30 Mar 2021 10:10:02 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: Mike Kravetz <mike.kravetz@...cle.com>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>
CC: Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
Shakeel Butt <shakeelb@...gle.com>,
Oscar Salvador <osalvador@...e.de>,
David Hildenbrand <david@...hat.com>,
Muchun Song <songmuchun@...edance.com>,
David Rientjes <rientjes@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Matthew Wilcox <willy@...radead.org>,
HORIGUCHI NAOYA <naoya.horiguchi@....com>,
"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
Mina Almasry <almasrymina@...gle.com>,
"Hillf Danton" <hdanton@...a.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Barry Song <song.bao.hua@...ilicon.com>,
Will Deacon <will@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 5/8] hugetlb: call update_and_free_page without
hugetlb_lock
On 2021/3/30 7:23, Mike Kravetz wrote:
> 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.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Reviewed-by: Muchun Song <songmuchun@...edance.com>
Looks good to me. Thanks!
Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
> mm/hugetlb.c | 32 +++++++++++++++++++++++++++-----
> 1 file changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 16beabbbbe49..dec7bd0dc63d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1451,16 +1451,18 @@ static void __free_huge_page(struct page *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);
> }
>
> /*
> @@ -1741,7 +1743,13 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
> 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;
> }
> @@ -1810,8 +1818,9 @@ int dissolve_free_huge_page(struct page *page)
> }
> 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);
> @@ -2674,22 +2683,35 @@ static void try_to_free_low(struct hstate *h, unsigned long count,
> 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
> + */
> + INIT_LIST_HEAD(&page_list);
> 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,
>
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