From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 7C51C6B02FA for ; Tue, 25 Apr 2017 08:57:16 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id 72so30703895pge.10 for ; Tue, 25 Apr 2017 05:57:16 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTPS id a90si22400448plc.67.2017.04.25.05.57.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Apr 2017 05:57:15 -0700 (PDT) From: "Huang, Ying" 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> In-Reply-To: <20170425125658.28684-1-ying.huang@intel.com> References: <20170425125658.28684-1-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 , Johannes Weiner 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 -- 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