From: Oscar Salvador <osalvador@suse.de>
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,
mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com,
naoya.horiguchi@nec.com, duanxiongchun@bytedance.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v10 04/11] mm/hugetlb: Defer freeing of HugeTLB pages
Date: Mon, 21 Dec 2020 11:27:07 +0100 [thread overview]
Message-ID: <20201221102703.GA15804@linux> (raw)
In-Reply-To: <20201217121303.13386-5-songmuchun@bytedance.com>
On Thu, Dec 17, 2020 at 08:12:56PM +0800, 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 from using GFP_ATOMIC to allocate the vmemmap
> pages.
I think we would benefit from a more complete changelog, at least I had
to stare at the code for a while in order to grasp what are we trying
to do and the reasons behind.
> +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.
The above implies that update_and_free_page() is __always__ called from a
non-task context, but that is not always the case?
> +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);
I wonder if this should be moved to hugetlb_vmemmap.c
> +/*
> + * This is where the call to allocate vmemmmap pages will be inserted.
> + */
I think this should go in the changelog.
> +static void __free_hugepage(struct hstate *h, struct page *page)
> +{
> + int i;
> +
> 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 +1377,17 @@ 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
> + * context do not hold the hugetlb_lock), because we might
> + * block in free_gigantic_page().
"
/*
* Temporarily drop the hugetlb_lock, because we might block
* in free_gigantic_page(). Only drop it in case the vmemmap
* optimization is disabled, since that context does not hold
* the lock.
*/
" ?
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2020-12-21 10:28 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 12:12 [PATCH v10 00/11] Free some vmemmap pages of HugeTLB page Muchun Song
2020-12-17 12:12 ` [PATCH v10 01/11] mm/memory_hotplug: Factor out bootmem core functions to bootmem_info.c Muchun Song
2020-12-17 12:12 ` [PATCH v10 02/11] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-12-18 15:41 ` Oscar Salvador
2020-12-21 23:56 ` Mike Kravetz
2020-12-17 12:12 ` [PATCH v10 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page Muchun Song
2020-12-21 9:11 ` Oscar Salvador
2020-12-21 11:25 ` [External] " Muchun Song
2020-12-21 13:43 ` Oscar Salvador
2020-12-21 15:52 ` Muchun Song
2020-12-21 18:00 ` Oscar Salvador
2020-12-22 1:03 ` Mike Kravetz
2020-12-22 2:49 ` Muchun Song
2020-12-17 12:12 ` [PATCH v10 04/11] mm/hugetlb: Defer freeing of HugeTLB pages Muchun Song
2020-12-21 10:27 ` Oscar Salvador [this message]
2020-12-21 11:07 ` [External] " Muchun Song
2020-12-21 14:14 ` Oscar Salvador
2020-12-21 15:18 ` Muchun Song
2020-12-17 12:12 ` [PATCH v10 05/11] mm/hugetlb: Allocate the vmemmap pages associated with each HugeTLB page Muchun Song
2020-12-17 12:12 ` [PATCH v10 06/11] mm/hugetlb: Set the PageHWPoison to the raw error page Muchun Song
2020-12-17 12:12 ` [PATCH v10 07/11] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-12-21 10:40 ` Oscar Salvador
2020-12-21 11:07 ` [External] " Muchun Song
2020-12-17 12:13 ` [PATCH v10 08/11] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-12-17 12:13 ` [PATCH v10 09/11] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-12-21 8:16 ` Oscar Salvador
2020-12-21 9:33 ` [External] " Muchun Song
2020-12-17 12:13 ` [PATCH v10 10/11] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-12-18 9:06 ` Oscar Salvador
2020-12-18 9:41 ` [External] " Muchun Song
2020-12-17 12:13 ` [PATCH v10 11/11] mm/hugetlb: Optimize the code with the help of the compiler Muchun Song
2020-12-17 12:17 ` [PATCH v10 00/11] Free some vmemmap pages of HugeTLB page David Hildenbrand
2020-12-17 14:59 ` Oscar Salvador
2020-12-17 15:52 ` [External] " Muchun Song
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