From: Michal Hocko <mhocko@suse.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, paulmck@kernel.org,
mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com,
rdunlap@infradead.org, oneukum@suse.com,
anshuman.khandual@arm.com, jroedel@suse.de,
almasrymina@google.com, rientjes@google.com, willy@infradead.org,
osalvador@suse.de, song.bao.hua@hisilicon.com, david@redhat.com,
naoya.horiguchi@nec.com, joao.m.martins@oracle.com,
duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, Chen Huang <chenhuang5@huawei.com>,
Bodeddula Balasubramaniam <bodeddub@amazon.com>
Subject: Re: [PATCH v18 4/9] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page
Date: Wed, 10 Mar 2021 16:19:39 +0100 [thread overview]
Message-ID: <YEjji9oAwHuZaZEt@dhcp22.suse.cz> (raw)
In-Reply-To: <20210308102807.59745-5-songmuchun@bytedance.com>
On Mon 08-03-21 18:28:02, Muchun Song wrote:
[...]
> -static void update_and_free_page(struct hstate *h, struct page *page)
> +static int update_and_free_page(struct hstate *h, struct page *page)
> + __releases(&hugetlb_lock) __acquires(&hugetlb_lock)
> {
> int i;
> struct page *subpage = page;
> + int nid = page_to_nid(page);
>
> if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
> - return;
> + return 0;
>
> h->nr_huge_pages--;
> - h->nr_huge_pages_node[page_to_nid(page)]--;
> + h->nr_huge_pages_node[nid]--;
> + VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
> + VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
> + set_page_refcounted(page);
> + set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
> +
> + /*
> + * If the vmemmap pages associated with the HugeTLB page can be
> + * optimized or the page is gigantic, we might block in
> + * alloc_huge_page_vmemmap() or free_gigantic_page(). In both
> + * cases, drop the hugetlb_lock.
> + */
> + if (free_vmemmap_pages_per_hpage(h) || hstate_is_gigantic(h))
> + spin_unlock(&hugetlb_lock);
> +
> + if (alloc_huge_page_vmemmap(h, page)) {
> + spin_lock(&hugetlb_lock);
> + INIT_LIST_HEAD(&page->lru);
> + set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
> + h->nr_huge_pages++;
> + h->nr_huge_pages_node[nid]++;
> +
> + /*
> + * If we cannot allocate vmemmap pages, just refuse to free the
> + * page and put the page back on the hugetlb free list and treat
> + * as a surplus page.
> + */
> + h->surplus_huge_pages++;
> + h->surplus_huge_pages_node[nid]++;
> +
> + /*
> + * The refcount can possibly be increased by memory-failure or
> + * soft_offline handlers.
This comment could be more helpful. I believe you want to say this
/*
* HWpoisoning code can increment the reference
* count here. If there is a race then bail out
* the holder of the additional reference count will
* free up the page with put_page.
> + */
> + if (likely(put_page_testzero(page))) {
> + arch_clear_hugepage_flags(page);
> + enqueue_huge_page(h, page);
> + }
> +
> + return -ENOMEM;
> + }
> +
> for (i = 0; i < pages_per_huge_page(h);
> i++, subpage = mem_map_next(subpage, page, i)) {
> subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
[...]
> @@ -1447,7 +1486,7 @@ void free_huge_page(struct page *page)
> /*
> * Defer freeing if in non-task context to avoid hugetlb_lock deadlock.
> */
> - if (!in_task()) {
> + if (in_atomic()) {
As I've said elsewhere in_atomic doesn't work for CONFIG_PREEMPT_COUNT=n.
We need this change for other reasons and so it would be better to pull
it out into a separate patch which also makes HUGETLB depend on
PREEMPT_COUNT.
[...]
> @@ -1771,8 +1813,12 @@ int dissolve_free_huge_page(struct page *page)
> h->free_huge_pages--;
> h->free_huge_pages_node[nid]--;
> h->max_huge_pages--;
> - update_and_free_page(h, head);
> - rc = 0;
> + rc = update_and_free_page(h, head);
> + if (rc) {
> + h->surplus_huge_pages--;
> + h->surplus_huge_pages_node[nid]--;
> + h->max_huge_pages++;
This is quite ugly and confusing. update_and_free_page is careful to do
the proper counters accounting and now you just override it partially.
Why cannot we rely on update_and_free_page do the right thing?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-10 15:20 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 10:27 [PATCH v18 0/9] Free some vmemmap pages of HugeTLB page Muchun Song
2021-03-08 10:27 ` [PATCH v18 1/9] mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c Muchun Song
2021-03-10 14:14 ` Michal Hocko
2021-03-11 2:58 ` [External] " Muchun Song
2021-03-11 8:45 ` Muchun Song
2021-03-11 8:53 ` Michal Hocko
2021-03-11 9:05 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 2/9] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2021-03-08 10:28 ` [PATCH v18 3/9] mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Muchun Song
2021-03-10 14:32 ` Michal Hocko
2021-03-11 3:35 ` [External] " Muchun Song
2021-03-08 10:28 ` [PATCH v18 4/9] mm: hugetlb: alloc " Muchun Song
2021-03-10 14:21 ` Oscar Salvador
2021-03-11 4:13 ` [External] " Muchun Song
2021-03-10 15:19 ` Michal Hocko [this message]
2021-03-10 18:56 ` Mike Kravetz
2021-03-10 21:11 ` Michal Hocko
2021-03-10 21:49 ` Paul E. McKenney
2021-03-10 22:10 ` Mike Kravetz
2021-03-10 23:28 ` Paul E. McKenney
2021-03-11 8:40 ` Michal Hocko
2021-03-11 12:17 ` Michal Hocko
2021-03-11 17:59 ` Mike Kravetz
2021-03-11 22:53 ` Mike Kravetz
2021-03-12 8:15 ` Michal Hocko
2021-03-12 17:50 ` Mike Kravetz
2021-03-11 4:26 ` [External] " Muchun Song
2021-03-11 8:46 ` Michal Hocko
2021-03-11 8:49 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 5/9] mm: hugetlb: set the PageHWPoison to the raw error page Muchun Song
2021-03-10 15:27 ` Michal Hocko
2021-03-11 6:34 ` [External] " Muchun Song
2021-03-11 8:50 ` Michal Hocko
2021-03-11 9:13 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 6/9] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Muchun Song
2021-03-10 15:37 ` Michal Hocko
2021-03-10 17:15 ` Randy Dunlap
2021-03-11 6:36 ` [External] " Muchun Song
2021-03-11 6:36 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 7/9] mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2021-03-08 10:28 ` [PATCH v18 8/9] mm: hugetlb: gather discrete indexes of tail page Muchun Song
2021-03-10 15:39 ` Michal Hocko
2021-03-08 10:28 ` [PATCH v18 9/9] mm: hugetlb: optimize the code with the help of the compiler Muchun Song
2021-03-10 15:41 ` Michal Hocko
2021-03-11 7:33 ` [External] " Muchun Song
2021-03-11 8:55 ` Michal Hocko
2021-03-11 9:08 ` Muchun Song
2021-03-11 9:39 ` Michal Hocko
2021-03-11 10:00 ` Muchun Song
2021-03-11 12:16 ` Michal Hocko
2021-03-11 13:00 ` Muchun Song
2021-03-11 13:45 ` Oscar Salvador
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