From: Muchun Song <songmuchun@bytedance.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
Thomas Gleixner <tglx@linutronix.de>,
mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
dave.hansen@linux.intel.com, luto@kernel.org,
Peter Zijlstra <peterz@infradead.org>,
viro@zeniv.linux.org.uk,
Andrew Morton <akpm@linux-foundation.org>,
paulmck@kernel.org, mchehab+huawei@kernel.org,
pawan.kumar.gupta@linux.intel.com,
Randy Dunlap <rdunlap@infradead.org>,
oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de,
Mina Almasry <almasrymina@google.com>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Oscar Salvador <osalvador@suse.de>,
Michal Hocko <mhocko@suse.com>,
"Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
David Hildenbrand <david@redhat.com>,
Xiongchun duan <duanxiongchun@bytedance.com>,
linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [External] Re: [PATCH v9 04/11] mm/hugetlb: Defer freeing of HugeTLB pages
Date: Thu, 17 Dec 2020 11:19:21 +0800 [thread overview]
Message-ID: <CAMZfGtUu7P2eJSv9jhLWxaYsNidHZZpDPSTZLC7VprMaLKmgmg@mail.gmail.com> (raw)
In-Reply-To: <6b555fb8-6fd5-049a-49c1-4dc8a3f66766@oracle.com>
On Thu, Dec 17, 2020 at 7:48 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 12/13/20 7:45 AM, Muchun Song wrote:
> > In the subsequent patch, we will allocate the vmemmap pages when free
> > HugeTLB pages. But update_and_free_page() is called from a non-task
> > context(and hold hugetlb_lock), so we can defer the actual freeing in
> > a workqueue to prevent use GFP_ATOMIC to allocate the vmemmap pages.
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>
> It is unfortunate we need to add this complexitty, but I can not think
> of another way. One small comment (no required change) below.
>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Thank you.
>
> > ---
> > mm/hugetlb.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++----
> > mm/hugetlb_vmemmap.c | 12 --------
> > mm/hugetlb_vmemmap.h | 17 ++++++++++++
> > 3 files changed, 88 insertions(+), 18 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 140135fc8113..0ff9b90e524f 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1292,15 +1292,76 @@ static inline void destroy_compound_gigantic_page(struct page *page,
> > unsigned int order) { }
> > #endif
> >
> > -static void update_and_free_page(struct hstate *h, struct page *page)
> > +static void __free_hugepage(struct hstate *h, struct page *page);
> > +
> > +/*
> > + * As update_and_free_page() is be called from a non-task context(and hold
> > + * hugetlb_lock), we can defer the actual freeing in a workqueue to prevent
> > + * use GFP_ATOMIC to allocate a lot of vmemmap pages.
> > + *
> > + * update_hpage_vmemmap_workfn() locklessly retrieves the linked list of
> > + * pages to be freed and frees them one-by-one. As the page->mapping pointer
> > + * is going to be cleared in update_hpage_vmemmap_workfn() anyway, it is
> > + * reused as the llist_node structure of a lockless linked list of huge
> > + * pages to be freed.
> > + */
> > +static LLIST_HEAD(hpage_update_freelist);
> > +
> > +static void update_hpage_vmemmap_workfn(struct work_struct *work)
> > {
> > - int i;
> > + struct llist_node *node;
> > + struct page *page;
> > +
> > + node = llist_del_all(&hpage_update_freelist);
> >
> > + while (node) {
> > + page = container_of((struct address_space **)node,
> > + struct page, mapping);
> > + node = node->next;
> > + page->mapping = NULL;
> > + __free_hugepage(page_hstate(page), page);
> > +
> > + cond_resched();
> > + }
> > +}
> > +static DECLARE_WORK(hpage_update_work, update_hpage_vmemmap_workfn);
> > +
> > +static inline void __update_and_free_page(struct hstate *h, struct page *page)
> > +{
> > + /* No need to allocate vmemmap pages */
> > + if (!free_vmemmap_pages_per_hpage(h)) {
> > + __free_hugepage(h, page);
> > + return;
> > + }
> > +
> > + /*
> > + * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap
> > + * pages.
> > + *
> > + * Only call schedule_work() if hpage_update_freelist is previously
> > + * empty. Otherwise, schedule_work() had been called but the workfn
> > + * hasn't retrieved the list yet.
> > + */
> > + if (llist_add((struct llist_node *)&page->mapping,
> > + &hpage_update_freelist))
> > + schedule_work(&hpage_update_work);
> > +}
> > +
> > +static void update_and_free_page(struct hstate *h, struct page *page)
> > +{
> > if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
> > return;
> >
> > h->nr_huge_pages--;
> > h->nr_huge_pages_node[page_to_nid(page)]--;
> > +
> > + __update_and_free_page(h, page);
> > +}
> > +
> > +static void __free_hugepage(struct hstate *h, struct page *page)
> > +{
> > + int i;
> > +
>
> Can we add a comment here saying that this is where the call to allocate
> vmemmmap pages will be inserted in a later patch. Such a comment would
> help a bit to understand the restructuring of the code.
OK. Will do. Thanks.
>
> --
> Mike Kravetz
>
> > for (i = 0; i < pages_per_huge_page(h); i++) {
> > page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
> > 1 << PG_referenced | 1 << PG_dirty |
> > @@ -1313,13 +1374,17 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> > set_page_refcounted(page);
> > if (hstate_is_gigantic(h)) {
> > /*
> > - * Temporarily drop the hugetlb_lock, because
> > - * we might block in free_gigantic_page().
> > + * Temporarily drop the hugetlb_lock only when this type of
> > + * HugeTLB page does not support vmemmap optimization (which
> > + * contex do not hold the hugetlb_lock), because we might block
> > + * in free_gigantic_page().
> > */
> > - spin_unlock(&hugetlb_lock);
> > + if (!free_vmemmap_pages_per_hpage(h))
> > + spin_unlock(&hugetlb_lock);
> > destroy_compound_gigantic_page(page, huge_page_order(h));
> > free_gigantic_page(page, huge_page_order(h));
> > - spin_lock(&hugetlb_lock);
> > + if (!free_vmemmap_pages_per_hpage(h))
> > + spin_lock(&hugetlb_lock);
> > } else {
> > __free_pages(page, huge_page_order(h));
> > }
--
Yours,
Muchun
next prev parent reply other threads:[~2020-12-17 3:20 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-13 15:45 [PATCH v9 00/11] Free some vmemmap pages of HugeTLB page Muchun Song
2020-12-13 15:45 ` [PATCH v9 01/11] mm/memory_hotplug: Factor out bootmem core functions to bootmem_info.c Muchun Song
2020-12-13 15:45 ` [PATCH v9 02/11] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-12-16 1:03 ` Mike Kravetz
2020-12-16 3:24 ` [External] " Muchun Song
2020-12-16 3:45 ` Mike Kravetz
2020-12-16 3:52 ` [External] " Muchun Song
2020-12-13 15:45 ` [PATCH v9 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page Muchun Song
2020-12-16 13:06 ` Oscar Salvador
2020-12-16 13:15 ` [External] " Muchun Song
2020-12-16 22:08 ` Mike Kravetz
2020-12-16 22:25 ` Oscar Salvador
2020-12-16 22:49 ` Mike Kravetz
2020-12-17 6:54 ` [External] " Muchun Song
2020-12-17 9:05 ` Muchun Song
2020-12-17 4:06 ` Muchun Song
2020-12-13 15:45 ` [PATCH v9 04/11] mm/hugetlb: Defer freeing of HugeTLB pages Muchun Song
2020-12-16 23:48 ` Mike Kravetz
2020-12-17 3:19 ` Muchun Song [this message]
2020-12-13 15:45 ` [PATCH v9 05/11] mm/hugetlb: Allocate the vmemmap pages associated with each HugeTLB page Muchun Song
2020-12-17 1:17 ` Mike Kravetz
2020-12-17 3:22 ` [External] " Muchun Song
2020-12-13 15:45 ` [PATCH v9 06/11] mm/hugetlb: Set the PageHWPoison to the raw error page Muchun Song
2020-12-16 13:28 ` Oscar Salvador
2020-12-16 13:51 ` [External] " Muchun Song
2020-12-16 13:30 ` Oscar Salvador
2020-12-13 15:45 ` [PATCH v9 07/11] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-12-13 15:45 ` [PATCH v9 08/11] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-12-16 14:40 ` Oscar Salvador
2020-12-16 16:04 ` [External] " Muchun Song
2020-12-16 22:10 ` Oscar Salvador
2020-12-17 2:45 ` Muchun Song
2020-12-13 15:45 ` [PATCH v9 09/11] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-12-16 13:43 ` Oscar Salvador
2020-12-16 13:56 ` [External] " Muchun Song
2020-12-16 22:12 ` Oscar Salvador
2020-12-17 8:34 ` Muchun Song
2020-12-13 15:45 ` [PATCH v9 10/11] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-12-16 14:03 ` Oscar Salvador
2020-12-16 14:26 ` [External] " Muchun Song
2020-12-13 15:45 ` [PATCH v9 11/11] mm/hugetlb: Optimize the code with the help of the compiler Muchun Song
2020-12-17 10:31 ` Oscar Salvador
2020-12-17 10:42 ` [External] " Muchun Song
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