Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752392AbbHTQUL (ORCPT ); Thu, 20 Aug 2015 12:20:11 -0400 Received: from forward-corp1g.mail.yandex.net ([95.108.253.251]:58694 "EHLO forward-corp1g.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751858AbbHTQUJ (ORCPT ); Thu, 20 Aug 2015 12:20:09 -0400 Authentication-Results: smtpcorp4.mail.yandex.net; dkim=pass header.i=@yandex-team.ru From: Roman Gushchin To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Roman Gushchin , Linus Torvalds , Raghavendra K T , Jan Kara , Wu Fengguang , David Rientjes , Andrew Morton Subject: [PATCH] mm/readahead.c: fix regression caused by small readahead limit Date: Thu, 20 Aug 2015 19:19:58 +0300 Message-Id: <1440087598-27185-1-git-send-email-klamm@yandex-team.ru> X-Mailer: git-send-email 2.4.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2352 Lines: 75 Effectively reverts: 6d2be915e589b58cb11418cbe1f22ff90732b6ac ("mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages"). This commit causes significant i/o performance regression on large RAID disks. Limiting maximal readahead size by 2Mb is not suitable for this case, alghough previous logic (based on free memory size on current NUMA node) is much better. To avoid regression in case of memoryless NUMA we can still use MAX_READAHEAD constant, if current node has no (or less) free memory. before: $ dd if=/dev/md2 of=/dev/null bs=100M count=100 100+0 records in 100+0 records out 10485760000 bytes (10 GB) copied, 12.6441 s, 829 MB/s $ dd if=/dev/md2 of=/dev/null bs=100M count=100 iflag=direct 100+0 records in 100+0 records out 10485760000 bytes (10 GB) copied, 9.49377 s, 1.1 GB/s after: $ dd if=/dev/md2 of=/dev/null bs=100M count=100 100+0 records in 100+0 records out 10485760000 bytes (10 GB) copied, 9.18119 s, 1.1 GB/s $ dd if=/dev/md2 of=/dev/null bs=100M count=100 iflag=direct 100+0 records in 100+0 records out 10485760000 bytes (10 GB) copied, 9.34751 s, 1.1 GB/s (It's 8 disks RAID 5 with 1024k chunk.) Signed-off-by: Roman Gushchin Cc: Linus Torvalds Cc: Raghavendra K T Cc: Jan Kara Cc: Wu Fengguang Cc: David Rientjes Cc: Andrew Morton --- mm/readahead.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/readahead.c b/mm/readahead.c index 60cd846..93a00b3 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -239,7 +239,12 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, */ unsigned long max_sane_readahead(unsigned long nr) { - return min(nr, MAX_READAHEAD); + unsigned long max_sane; + + max_sane = max(MAX_READAHEAD, + (node_page_state(numa_node_id(), NR_INACTIVE_FILE) + + node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2); + return min(nr, max_sane); } /* -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/