From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752087AbdHGFmD (ORCPT ); Mon, 7 Aug 2017 01:42:03 -0400 Received: from mga06.intel.com ([134.134.136.31]:24924 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962AbdHGFmB (ORCPT ); Mon, 7 Aug 2017 01:42:01 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,336,1498546800"; d="scan'208";a="1202767440" From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Johannes Weiner , Minchan Kim , Rik van Riel , Shaohua Li , Hugh Dickins , Fengguang Wu , Tim Chen , Dave Hansen Subject: [PATCH -mm -v4 2/5] mm, swap: Fix swap readahead marking Date: Mon, 7 Aug 2017 13:40:35 +0800 Message-Id: <20170807054038.1843-3-ying.huang@intel.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170807054038.1843-1-ying.huang@intel.com> References: <20170807054038.1843-1-ying.huang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huang Ying In the original implementation, it is possible that the existing pages in the swap cache (not newly readahead) could be marked as the readahead pages. This will cause the statistics of swap readahead be wrong and influence the swap readahead algorithm too. This is fixed via marking a page as the readahead page only if it is newly allocated and read from the disk. When testing with linpack, after the fixing the swap readahead hit rate increased from ~66% to ~86%. Signed-off-by: "Huang, Ying" Cc: Johannes Weiner Cc: Minchan Kim Cc: Rik van Riel Cc: Shaohua Li Cc: Hugh Dickins Cc: Fengguang Wu Cc: Tim Chen Cc: Dave Hansen --- mm/swap_state.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index d1bdb31cab13..a901afe9da61 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -498,7 +498,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, unsigned long start_offset, end_offset; unsigned long mask; struct blk_plug plug; - bool do_poll = true; + bool do_poll = true, page_allocated; mask = swapin_nr_pages(offset) - 1; if (!mask) @@ -514,14 +514,18 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, blk_start_plug(&plug); for (offset = start_offset; offset <= end_offset ; offset++) { /* Ok, do the async read-ahead now */ - page = read_swap_cache_async(swp_entry(swp_type(entry), offset), - gfp_mask, vma, addr, false); + page = __read_swap_cache_async( + swp_entry(swp_type(entry), offset), + gfp_mask, vma, addr, &page_allocated); if (!page) continue; - if (offset != entry_offset && - likely(!PageTransCompound(page))) { - SetPageReadahead(page); - count_vm_event(SWAP_RA); + if (page_allocated) { + swap_readpage(page, false); + if (offset != entry_offset && + likely(!PageTransCompound(page))) { + SetPageReadahead(page); + count_vm_event(SWAP_RA); + } } put_page(page); } -- 2.11.0