From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 4A9AF6B03AF for ; Wed, 8 Mar 2017 02:26:52 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id l66so44315136pfl.6 for ; Tue, 07 Mar 2017 23:26:52 -0800 (PST) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTPS id y70si2425223plh.168.2017.03.07.23.26.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Mar 2017 23:26:51 -0800 (PST) From: "Huang, Ying" Subject: [PATCH -mm -v6 7/9] mm, THP: Add can_split_huge_page() Date: Wed, 8 Mar 2017 15:26:11 +0800 Message-Id: <20170308072613.17634-8-ying.huang@intel.com> In-Reply-To: <20170308072613.17634-1-ying.huang@intel.com> References: <20170308072613.17634-1-ying.huang@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Andrea Arcangeli , Ebru Akagunduz From: Huang Ying Separates checking whether we can split the huge page from split_huge_page_to_list() into a function. This will help to check that before splitting the THP (Transparent Huge Page) really. This will be used for delaying splitting THP during swapping out. Where for a THP, we will allocate a swap cluster, add the THP into the swap cache, then split the THP. To avoid the unnecessary operations for the un-splittable THP, we will check that firstly. There is no functionality change in this patch. Cc: Andrea Arcangeli Cc: Ebru Akagunduz Signed-off-by: "Huang, Ying" Acked-by: Kirill A. Shutemov --- include/linux/huge_mm.h | 7 +++++++ mm/huge_memory.c | 17 ++++++++++++++--- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index a3762d49ba39..d3b3e8fcc717 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -113,6 +113,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp, extern void prep_transhuge_page(struct page *page); extern void free_transhuge_page(struct page *page); +bool can_split_huge_page(struct page *page, int *pextra_pins); int split_huge_page_to_list(struct page *page, struct list_head *list); static inline int split_huge_page(struct page *page) { @@ -231,6 +232,12 @@ static inline void prep_transhuge_page(struct page *page) {} #define thp_get_unmapped_area NULL +static inline bool +can_split_huge_page(struct page *page, int *pextra_pins) +{ + BUILD_BUG(); + return false; +} static inline int split_huge_page_to_list(struct page *page, struct list_head *list) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2b4120f6930c..45f944db43b0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2362,6 +2362,19 @@ int page_trans_huge_mapcount(struct page *page, int *total_mapcount) return ret; } +/* Racy check whether the huge page can be split */ +bool can_split_huge_page(struct page *page, int *pextra_pins) +{ + int extra_pins = 0; + + /* Additional pins from radix tree */ + if (!PageAnon(page)) + extra_pins = HPAGE_PMD_NR; + if (pextra_pins) + *pextra_pins = extra_pins; + return total_mapcount(page) == page_count(page) - extra_pins - 1; +} + /* * This function splits huge page into normal pages. @page can point to any * subpage of huge page to split. Split doesn't change the position of @page. @@ -2421,8 +2434,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) goto out; } - /* Addidional pins from radix tree */ - extra_pins = HPAGE_PMD_NR; anon_vma = NULL; i_mmap_lock_read(mapping); } @@ -2431,7 +2442,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) * Racy check if we can split the page, before freeze_page() will * split PMDs */ - if (total_mapcount(head) != page_count(head) - extra_pins - 1) { + if (!can_split_huge_page(head, &extra_pins)) { ret = -EBUSY; goto out_unlock; } -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org