From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756044AbdDFFgB (ORCPT ); Thu, 6 Apr 2017 01:36:01 -0400 Received: from mga07.intel.com ([134.134.136.100]:19157 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755745AbdDFFfx (ORCPT ); Thu, 6 Apr 2017 01:35:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,282,1488873600"; d="scan'208";a="85359297" From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Johannes Weiner Subject: [PATCH -mm -v8 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map Date: Thu, 6 Apr 2017 13:35:15 +0800 Message-Id: <20170406053515.4842-4-ying.huang@intel.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170406053515.4842-1-ying.huang@intel.com> References: <20170406053515.4842-1-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 | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 612fb2418df6..528af29327c9 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -205,7 +205,9 @@ int add_to_swap(struct page *page, struct list_head *list) /* cannot split, skip it */ if (!can_split_huge_page(page, NULL)) return 0; - huge = true; + /* fallback to split huge page firstly if no PMD map */ + if (compound_mapcount(page)) + huge = true; } #endif -- 2.11.0