From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f71.google.com (mail-pa0-f71.google.com [209.85.220.71]) by kanga.kvack.org (Postfix) with ESMTP id E3B74828F0 for ; Tue, 9 Aug 2016 12:38:30 -0400 (EDT) Received: by mail-pa0-f71.google.com with SMTP id ez1so30850198pab.1 for ; Tue, 09 Aug 2016 09:38:30 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTP id x69si43400947pfi.273.2016.08.09.09.38.13 for ; Tue, 09 Aug 2016 09:38:13 -0700 (PDT) From: "Huang, Ying" Subject: [RFC 09/11] mm, THP: Add can_split_huge_page() Date: Tue, 9 Aug 2016 09:37:51 -0700 Message-Id: <1470760673-12420-10-git-send-email-ying.huang@intel.com> In-Reply-To: <1470760673-12420-1-git-send-email-ying.huang@intel.com> References: <1470760673-12420-1-git-send-email-ying.huang@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: tim.c.chen@intel.com, dave.hansen@intel.com, andi.kleen@intel.com, aaron.lu@intel.com, "Kirill A . Shutemov" , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , 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 swap cache, then split the THP. To avoid unnecessary operations for un-splittable THP, we will check that firstly. There is no functionality change in this patch. Cc: Andrea Arcangeli Cc: Kirill A. Shutemov Cc: Ebru Akagunduz Signed-off-by: "Huang, Ying" --- include/linux/huge_mm.h | 6 ++++++ mm/huge_memory.c | 13 ++++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 6f14de4..95ccbb4 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -90,6 +90,7 @@ extern unsigned long transparent_hugepage_flags; 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 split_huge_page_to_list(struct page *page, struct list_head *list); static inline int split_huge_page(struct page *page) { @@ -169,6 +170,11 @@ void put_huge_zero_page(void); static inline void prep_transhuge_page(struct page *page) {} #define transparent_hugepage_flags 0UL +static inline bool +can_split_huge_page(struct page *page) +{ + 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 2373f0a..af65413 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1954,6 +1954,17 @@ 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 extra_pins = 0; + + /* Additional pins from radix tree */ + if (!PageAnon(page)) + extra_pins = HPAGE_PMD_NR; + 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. @@ -2024,7 +2035,7 @@ 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)) { ret = -EBUSY; goto out_unlock; } -- 2.8.1 -- 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