From: Mike Kravetz <mike.kravetz@oracle.com>
To: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>,
Oscar Salvador <osalvador@suse.de>,
David Hildenbrand <david@redhat.com>,
Muchun Song <songmuchun@bytedance.com>,
David Rientjes <rientjes@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Peter Zijlstra <peterz@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
Mina Almasry <almasrymina@google.com>,
Hillf Danton <hdanton@sina.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 5/8] hugetlb: call update_and_free_page without hugetlb_lock
Date: Thu, 25 Mar 2021 10:12:05 -0700 [thread overview]
Message-ID: <d60a13c9-24c0-1d24-85bc-08a0090d282e@oracle.com> (raw)
In-Reply-To: <YFxsB4YLXCobtGGv@dhcp22.suse.cz>
On 3/25/21 3:55 AM, Michal Hocko wrote:
> On Wed 24-03-21 17:28:32, 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@oracle.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> One minor thing below
>
> [...]
>> @@ -2563,22 +2572,37 @@ static void try_to_free_low(struct hstate *h, unsigned long count,
>> nodemask_t *nodes_allowed)
>> {
>> int i;
>> + struct list_head page_list;
>> + struct page *page, *next;
>>
>> 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);
>> + INIT_LIST_HEAD(&page->lru);
>
> What is the point of rhis INIT_LIST_HEAD? Page has been removed from the
> list by remove_hugetlb_page so it can be added to a new one without any
> reinitialization.
remove_hugetlb_page just does a list_del. list_del will poison the
pointers in page->lru. The following list_add will then complain about
list corruption.
I could replace the list_del in remove_hugetlb_page with list_del_init.
However, not all callers of remove_hugetlb_page will be adding the page
to a list. If we just call update_and_free_page, there is no need to
reinitialize the list pointers.
Might be better to just use list_del_init in remove_hugetlb_page to
avoid any questions like this.
--
Mike Kravetz
>
>> + list_add(&page->lru, &page_list);
>> }
>> }
>> +
>> +out:
>> + spin_unlock(&hugetlb_lock);
>> + list_for_each_entry_safe(page, next, &page_list, lru) {
>> + list_del(&page->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,
>> --
>> 2.30.2
>>
>
next prev parent reply other threads:[~2021-03-25 17:12 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 0:28 [PATCH 0/8] make hugetlb put_page safe for all calling contexts Mike Kravetz
2021-03-25 0:28 ` [PATCH 1/8] mm: cma: introduce cma_release_nowait() Mike Kravetz
2021-03-25 9:39 ` Oscar Salvador
2021-03-25 9:45 ` Michal Hocko
2021-03-25 9:54 ` Oscar Salvador
2021-03-25 10:10 ` Michal Hocko
2021-03-25 10:11 ` Michal Hocko
2021-03-25 10:13 ` David Hildenbrand
2021-03-25 10:17 ` Oscar Salvador
2021-03-25 10:24 ` Michal Hocko
2021-03-25 9:56 ` David Hildenbrand
2021-03-25 10:22 ` Michal Hocko
2021-03-25 16:56 ` Mike Kravetz
2021-03-25 17:15 ` David Hildenbrand
2021-03-25 20:12 ` Minchan Kim
2021-03-25 23:19 ` Roman Gushchin
2021-03-25 23:49 ` Mike Kravetz
2021-03-26 21:32 ` Mike Kravetz
2021-03-29 7:46 ` Michal Hocko
2021-03-29 22:27 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 2/8] mm: hugetlb: don't drop hugetlb_lock around cma_release() call Mike Kravetz
2021-03-25 0:28 ` [PATCH 3/8] hugetlb: add per-hstate mutex to synchronize user adjustments Mike Kravetz
2021-03-25 10:47 ` Michal Hocko
2021-03-25 12:29 ` Oscar Salvador
2021-03-26 1:52 ` Miaohe Lin
2021-03-25 0:28 ` [PATCH 4/8] hugetlb: create remove_hugetlb_page() to separate functionality Mike Kravetz
2021-03-25 10:49 ` Michal Hocko
2021-03-26 2:10 ` Miaohe Lin
2021-03-26 19:57 ` Mike Kravetz
2021-03-27 1:40 ` Miaohe Lin
2021-03-27 6:36 ` [External] " Muchun Song
2021-03-25 0:28 ` [PATCH 5/8] hugetlb: call update_and_free_page without hugetlb_lock Mike Kravetz
2021-03-25 10:55 ` Michal Hocko
2021-03-25 17:12 ` Mike Kravetz [this message]
2021-03-25 19:39 ` Michal Hocko
2021-03-25 20:33 ` Mike Kravetz
2021-03-27 6:54 ` [External] " Muchun Song
2021-03-28 21:40 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 6/8] hugetlb: change free_pool_huge_page to remove_pool_huge_page Mike Kravetz
2021-03-25 11:06 ` Michal Hocko
2021-03-25 17:29 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 7/8] hugetlb: make free_huge_page irq safe Mike Kravetz
2021-03-25 11:21 ` Michal Hocko
2021-03-25 17:32 ` Mike Kravetz
2021-03-27 7:06 ` [External] " Muchun Song
2021-03-29 7:49 ` Michal Hocko
2021-03-29 22:44 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 8/8] hugetlb: add lockdep_assert_held() calls for hugetlb_lock Mike Kravetz
2021-03-25 11:22 ` Michal Hocko
2021-03-26 2:12 ` Miaohe Lin
2021-03-27 8:14 ` [External] " Muchun Song
2021-03-26 1:42 ` [PATCH 0/8] make hugetlb put_page safe for all calling contexts Miaohe Lin
2021-03-26 20:00 ` Mike Kravetz
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