From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754663AbcI2GfL (ORCPT ); Thu, 29 Sep 2016 02:35:11 -0400 Received: from mga14.intel.com ([192.55.52.115]:19476 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754903AbcI2GeZ (ORCPT ); Thu, 29 Sep 2016 02:34:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,413,1470726000"; d="scan'208";a="174441223" From: "Huang, Ying" To: Andrew Morton Cc: tim.c.chen@intel.com, dave.hansen@intel.com, andi.kleen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Andrea Arcangeli , "Kirill A . Shutemov" , Ebru Akagunduz Subject: [PATCH -v4 7/9] mm, THP: Add can_split_huge_page() Date: Thu, 29 Sep 2016 14:33:52 +0800 Message-Id: <20160929063354.1875-8-ying.huang@intel.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160929063354.1875-1-ying.huang@intel.com> References: <20160929063354.1875-1-ying.huang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: Kirill A. Shutemov Cc: Ebru Akagunduz Signed-off-by: "Huang, Ying" --- include/linux/huge_mm.h | 7 +++++++ mm/huge_memory.c | 13 ++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 9b9f65d..14ffa3f 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -94,6 +94,7 @@ 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 split_huge_page_to_list(struct page *page, struct list_head *list); static inline int split_huge_page(struct page *page) { @@ -176,6 +177,12 @@ 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) +{ + 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 1d558fc..c856a7c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2016,6 +2016,17 @@ 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. @@ -2086,7 +2097,7 @@ 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; } -- 2.9.3