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=-10.9 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,USER_AGENT_GIT autolearn=unavailable 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 63C29C4363D for ; Fri, 25 Sep 2020 12:54:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 249A82075E for ; Fri, 25 Sep 2020 12:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601038489; bh=8PR+7OGd/wvtWMCn9sP70IxmjSeqLsBEDbQSnvok9HA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=eO+9wxw0GM6rq1Du27JymSK7FwPKEQr/ZVME+Xqwhhhlois2eMZ6hb+NUckraqpgK NU48I+n9oTZElvZAvMYBy/1FeaMqvbSrpKE4v+bvOsKS0yHahz4GNgfZ3N4FsPSzn4 zVXdSA1jdgMka/AssGri5Tm3zU1T81ASG4VAxvJg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729609AbgIYMyr (ORCPT ); Fri, 25 Sep 2020 08:54:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:33712 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729601AbgIYMyo (ORCPT ); Fri, 25 Sep 2020 08:54:44 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 8AAD1206DB; Fri, 25 Sep 2020 12:54:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601038483; bh=8PR+7OGd/wvtWMCn9sP70IxmjSeqLsBEDbQSnvok9HA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1iI/iGr1ovgNHZlh8c5eOcAlrkvqCVCI0/TvRbE5Z+I3xCNhF4kz46GUHFO1QT9AB gPCAKaLKaTTeu6UKU5HhgVI0f4eqJOJylDbBwclUYpc1IJJrlN5niHNR7QI8cNjZ8O o+h7gQGPdNZzmiKjfgbIdmabT+0IramdVlDWU0kE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michal Hocko , Xunlei Pang , Andrew Morton , Chris Down , Johannes Weiner , Linus Torvalds , Julius Hemanth Pitti Subject: [PATCH 4.19 34/37] mm: memcg: fix memcg reclaim soft lockup Date: Fri, 25 Sep 2020 14:49:02 +0200 Message-Id: <20200925124726.085108517@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200925124720.972208530@linuxfoundation.org> References: <20200925124720.972208530@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xunlei Pang commit e3336cab2579012b1e72b5265adf98e2d6e244ad upstream. 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. Suggested-by: Michal Hocko Signed-off-by: Xunlei Pang Signed-off-by: Andrew Morton Acked-by: Chris Down Acked-by: Michal Hocko Acked-by: Johannes Weiner Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com Signed-off-by: Linus Torvalds Signed-off-by: Julius Hemanth Pitti Signed-off-by: Greg Kroah-Hartman --- mm/vmscan.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2708,6 +2708,14 @@ static bool shrink_node(pg_data_t *pgdat 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(); + switch (mem_cgroup_protected(root, memcg)) { case MEMCG_PROT_MIN: /*