From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A52E8C282DD for ; Thu, 9 Jan 2020 22:57:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DEFF2072E for ; Thu, 9 Jan 2020 22:57:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YuimSzZu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728488AbgAIW5O (ORCPT ); Thu, 9 Jan 2020 17:57:14 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:46874 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725840AbgAIW5O (ORCPT ); Thu, 9 Jan 2020 17:57:14 -0500 Received: by mail-pf1-f195.google.com with SMTP id n9so110126pff.13 for ; Thu, 09 Jan 2020 14:57:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=2a7Ek0VQLsAuhJ+XYFWJA3fva0Kgdtmci7QB6XNEMP0=; b=YuimSzZu1y5m9DZaeBFiFrcs4NDuyX4BeY681gPjsn3V/IeAf/sqbRvUwwcTyHtfNN umoLWe6WPMlrcdGJ0FrwedEmxnj53t9E1Cdld15ykhcJvlxI7rswAM6ZMAB2sOMehdgC n4cCwi7DocM+8RUKnFb9CiTA5vocgtyXiruGGYWC6tqBKzgrHYoSAnTKqKCqc0I5c1Pc jufAvkwoMSdUDwgwLke6LXNVyHmELFolGkhiPBQPNeVYpIFnGd4dwhSBNfYiqY3a4DNq t5qEToWYutjIhZZqIhZsh+ckC2MNihKpjPtIb68mlV7X5EjaftY3uKqzrIOfV7nRu4EA zyHQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=2a7Ek0VQLsAuhJ+XYFWJA3fva0Kgdtmci7QB6XNEMP0=; b=rRYWvPInm7pUuvxS2HERsFHwho+wqe8dEIyFUz+SJUxA4YpZXW087wXUOjlwTW2eyI Kvlerj4Ey1F8R7SirxsPuTai/wV5FgXmm7NCL1AVgG46OPkXzqmkOtXqHU/Sp7GEzZzV soD/UtnHPrpFFjBFc/QD/bvehnFHqSsY2PLCjKZgXug8eC0r9P2LRtFaZCkhkEJ1amWG UY3X8LLGSbhJjwoeLJUqk7Xatqu02ILW1Bx5JcrjZbMV+Lk2uAmqogRruFLH9gIc69m+ pT9dj+21WLWdg6yRPdqUSx5rANb54X20sNQNF8+iLNH9NpX3EMGW2QsJ/6SOpLJuSC/Z N4Yw== X-Gm-Message-State: APjAAAVJCUdfTRXGec/7IgMtTv9HioXY9mw3fQLu0MPv6oyqtSWco/es zuUZ4oiaRc0DCXpaCwT/Ta3qu+57r8E= X-Google-Smtp-Source: APXvYqySJ6jZ9DdfLLZGXudWsLWOQEN++HZ/J0SXS8CbNiwlcs4ZPLLbJ21gQqbWU1f5s62O3Fxn2g== X-Received: by 2002:a65:4c8b:: with SMTP id m11mr453079pgt.208.1578610633203; Thu, 09 Jan 2020 14:57:13 -0800 (PST) Received: from tw-172-25-31-76.office.twttr.net ([8.25.197.24]) by smtp.gmail.com with ESMTPSA id v9sm65662pja.26.2020.01.09.14.57.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 14:57:12 -0800 (PST) From: Cong Wang To: linux-kernel@vger.kernel.org Cc: Cong Wang , Andrew Morton , Michal Hocko , linux-mm@kvack.org Subject: [PATCH] mm: avoid blocking lock_page() in kcompactd Date: Thu, 9 Jan 2020 14:56:46 -0800 Message-Id: <20200109225646.22983-1-xiyou.wangcong@gmail.com> X-Mailer: git-send-email 2.21.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We observed kcompactd hung at __lock_page(): INFO: task kcompactd0:57 blocked for more than 120 seconds. Not tainted 4.19.56.x86_64 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kcompactd0 D 0 57 2 0x80000000 Call Trace: ? __schedule+0x236/0x860 schedule+0x28/0x80 io_schedule+0x12/0x40 __lock_page+0xf9/0x120 ? page_cache_tree_insert+0xb0/0xb0 ? update_pageblock_skip+0xb0/0xb0 migrate_pages+0x88c/0xb90 ? isolate_freepages_block+0x3b0/0x3b0 compact_zone+0x5f1/0x870 kcompactd_do_work+0x130/0x2c0 ? __switch_to_asm+0x35/0x70 ? __switch_to_asm+0x41/0x70 ? kcompactd_do_work+0x2c0/0x2c0 ? kcompactd+0x73/0x180 kcompactd+0x73/0x180 ? finish_wait+0x80/0x80 kthread+0x113/0x130 ? kthread_create_worker_on_cpu+0x50/0x50 ret_from_fork+0x35/0x40 which faddr2line maps to: migrate_pages+0x88c/0xb90: lock_page at include/linux/pagemap.h:483 (inlined by) __unmap_and_move at mm/migrate.c:1024 (inlined by) unmap_and_move at mm/migrate.c:1189 (inlined by) migrate_pages at mm/migrate.c:1419 Sometimes kcompactd eventually got out of this situation, sometimes not. I think for memory compaction, it is a best effort to migrate the pages, so it doesn't have to wait for I/O to complete. It is fine to call trylock_page() here, which is pretty much similar to buffer_migrate_lock_buffers(). Given MIGRATE_SYNC_LIGHT is used on compaction path, just relax the check for it. Cc: Andrew Morton Cc: Michal Hocko Cc: linux-mm@kvack.org Signed-off-by: Cong Wang --- mm/migrate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index 86873b6f38a7..df60026779d2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1010,7 +1010,8 @@ static int __unmap_and_move(struct page *page, struct page *newpage, bool is_lru = !__PageMovable(page); if (!trylock_page(page)) { - if (!force || mode == MIGRATE_ASYNC) + if (!force || mode == MIGRATE_ASYNC + || mode == MIGRATE_SYNC_LIGHT) goto out; /* -- 2.21.1