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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 34011C2BB84 for ; Fri, 4 Sep 2020 23:35:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E93D62087C for ; Fri, 4 Sep 2020 23:35:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599262530; bh=McC9JkzlgiqDtm84S0OpJILFQ702Wqlavhc8g5GZztc=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=QpzmMKRDKuEZC1mAVh8pHcp37GxujsvqQyEKU3PsIB+Nst3FjYuyp+a2wyp/e8oSh EO4e/tLM85YipVd0yIgDCvyJXeQV4WovdMWU7qoM5rau3a49dJYQA/FJezY4ta59EK /uLpcyartxtcQiSJjDia+WekYujIqVVVPGKaOeGI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726597AbgIDXf3 (ORCPT ); Fri, 4 Sep 2020 19:35:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:38388 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726456AbgIDXf2 (ORCPT ); Fri, 4 Sep 2020 19:35:28 -0400 Received: from localhost.localdomain (c-71-198-47-131.hsd1.ca.comcast.net [71.198.47.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CCED6208FE; Fri, 4 Sep 2020 23:35:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599262528; bh=McC9JkzlgiqDtm84S0OpJILFQ702Wqlavhc8g5GZztc=; h=Date:From:To:Subject:In-Reply-To:From; b=pqjIXMYLfrZM5NKaZzZurJ38iskOUrKhJy79fjYeRysgPQ7w+LSzym6M9JyN/LQDS jFXt65OR2N88BJu0GbDvdsxfmSNVwbQySBZKHZKs3Id4si7A8ORKW7U0Oa8Lzw4o9g 3T+xfZKPNV0RycWgjRzlaEIbAsDDgxF8EisjpEIw= Date: Fri, 04 Sep 2020 16:35:27 -0700 From: Andrew Morton To: akpm@linux-foundation.org, chris@chrisdown.name, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, xlpang@linux.alibaba.com Subject: [patch 02/19] mm: memcg: fix memcg reclaim soft lockup Message-ID: <20200904233527.1lOZT1GXC%akpm@linux-foundation.org> In-Reply-To: <20200904163454.4db0e6ce0c4584d2653678a3@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Xunlei Pang Subject: mm: memcg: fix memcg reclaim soft lockup We've met softlockup with "CONFIG_PREEMPT_NONE=y", when the target memcg doesn't have any reclaimable memory. It can be easily reproduced as below: watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204] CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12 Call Trace: shrink_lruvec+0x49f/0x640 shrink_node+0x2a6/0x6f0 do_try_to_free_pages+0xe9/0x3e0 try_to_free_mem_cgroup_pages+0xef/0x1f0 try_charge+0x2c1/0x750 mem_cgroup_charge+0xd7/0x240 __add_to_page_cache_locked+0x2fd/0x370 add_to_page_cache_lru+0x4a/0xc0 pagecache_get_page+0x10b/0x2f0 filemap_fault+0x661/0xad0 ext4_filemap_fault+0x2c/0x40 __do_fault+0x4d/0xf9 handle_mm_fault+0x1080/0x1790 It only happens on our 1-vcpu instances, because there's no chance for oom reaper to run to reclaim the to-be-killed process. Add a cond_resched() at the upper shrink_node_memcgs() to solve this issue, this will mean that we will get a scheduling point for each memcg in the reclaimed hierarchy without any dependency on the reclaimable memory in that memcg thus making it more predictable. Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com Signed-off-by: Xunlei Pang Acked-by: Chris Down Acked-by: Michal Hocko Suggested-by: Michal Hocko Acked-by: Johannes Weiner Signed-off-by: Andrew Morton --- mm/vmscan.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/vmscan.c~mm-memcg-fix-memcg-reclaim-soft-lockup +++ a/mm/vmscan.c @@ -2615,6 +2615,14 @@ static void shrink_node_memcgs(pg_data_t unsigned long reclaimed; unsigned long scanned; + /* + * This loop can become CPU-bound when target memcgs + * aren't eligible for reclaim - either because they + * don't have any reclaimable pages, or because their + * memory is explicitly protected. Avoid soft lockups. + */ + cond_resched(); + mem_cgroup_calculate_protection(target_memcg, memcg); if (mem_cgroup_below_min(memcg)) { _