From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947193AbdDYM5l (ORCPT ); Tue, 25 Apr 2017 08:57:41 -0400 Received: from mga11.intel.com ([192.55.52.93]:36510 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1430666AbdDYM5Q (ORCPT ); Tue, 25 Apr 2017 08:57:16 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,249,1488873600"; d="scan'208";a="960853842" From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Johannes Weiner Subject: [PATCH -mm -v10 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map Date: Tue, 25 Apr 2017 20:56:58 +0800 Message-Id: <20170425125658.28684-4-ying.huang@intel.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170425125658.28684-1-ying.huang@intel.com> References: <20170425125658.28684-1-ying.huang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huang Ying If there is no compound map for a THP (Transparent Huge Page), it is possible that the map count of some sub-pages of the THP is 0. So it is better to split the THP before swapping out. In this way, the sub-pages not mapped will be freed, and we can avoid the unnecessary swap out operations for these sub-pages. Cc: Johannes Weiner Signed-off-by: "Huang, Ying" --- mm/swap_state.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 006d91d8fc53..13f83c6bb1b4 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -192,9 +192,19 @@ int add_to_swap(struct page *page, struct list_head *list) VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageUptodate(page), page); - /* cannot split, skip it */ - if (PageTransHuge(page) && !can_split_huge_page(page, NULL)) - return 0; + if (PageTransHuge(page)) { + /* cannot split, skip it */ + if (!can_split_huge_page(page, NULL)) + return 0; + /* + * Split pages without a PMD map right away. Chances + * are some or all of the tail pages can be freed + * without IO. + */ + if (!compound_mapcount(page) && + split_huge_page_to_list(page, list)) + return 0; + } retry: entry = get_swap_page(page); -- 2.11.0