From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 26D288E0002 for ; Fri, 18 Jan 2019 12:52:50 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id e29so5312915ede.19 for ; Fri, 18 Jan 2019 09:52:50 -0800 (PST) Received: from outbound-smtp16.blacknight.com (outbound-smtp16.blacknight.com. [46.22.139.233]) by mx.google.com with ESMTPS id m3-v6si1788975ejb.316.2019.01.18.09.52.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Jan 2019 09:52:48 -0800 (PST) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp16.blacknight.com (Postfix) with ESMTPS id 341701C35B5 for ; Fri, 18 Jan 2019 17:52:48 +0000 (GMT) From: Mel Gorman Subject: [PATCH 06/22] mm, migrate: Immediately fail migration of a page with no migration handler Date: Fri, 18 Jan 2019 17:51:20 +0000 Message-Id: <20190118175136.31341-7-mgorman@techsingularity.net> In-Reply-To: <20190118175136.31341-1-mgorman@techsingularity.net> References: <20190118175136.31341-1-mgorman@techsingularity.net> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: David Rientjes , Andrea Arcangeli , Vlastimil Babka , Linux List Kernel Mailing , Linux-MM , Mel Gorman Pages with no migration handler use a fallback handler which sometimes works and sometimes persistently retries. A historical example was blockdev pages but there are others such as odd refcounting when page->private is used. These are retried multiple times which is wasteful during compaction so this patch will fail migration faster unless the caller specifies MIGRATE_SYNC. This is not expected to help THP allocation success rates but it did reduce latencies very slightly in some cases. 1-socket thpfioscale 4.20.0 4.20.0 noreserved-v2r15 failfast-v2r15 Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* Amean fault-both-3 3839.67 ( 0.00%) 3833.72 ( 0.15%) Amean fault-both-5 5177.47 ( 0.00%) 4967.15 ( 4.06%) Amean fault-both-7 7245.03 ( 0.00%) 7139.19 ( 1.46%) Amean fault-both-12 11534.89 ( 0.00%) 11326.30 ( 1.81%) Amean fault-both-18 16241.10 ( 0.00%) 16270.70 ( -0.18%) Amean fault-both-24 19075.91 ( 0.00%) 19839.65 ( -4.00%) Amean fault-both-30 22712.11 ( 0.00%) 21707.05 ( 4.43%) Amean fault-both-32 21692.92 ( 0.00%) 21968.16 ( -1.27%) The 2-socket results are not materially different. Scan rates are similar as expected. Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka --- mm/migrate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index 52b04c217e30..4512afab46ac 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -916,7 +916,7 @@ static int fallback_migrate_page(struct address_space *mapping, */ if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL)) - return -EAGAIN; + return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY; return migrate_page(mapping, newpage, page, mode); } -- 2.16.4