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=-1.0 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 0D338C43331 for ; Wed, 1 Apr 2020 16:12:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B10FB2071A for ; Wed, 1 Apr 2020 16:12:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B10FB2071A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 62EB38E0005; Wed, 1 Apr 2020 12:12:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5B74B8E0001; Wed, 1 Apr 2020 12:12:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 431798E0005; Wed, 1 Apr 2020 12:12:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0204.hostedemail.com [216.40.44.204]) by kanga.kvack.org (Postfix) with ESMTP id 25B618E0001 for ; Wed, 1 Apr 2020 12:12:47 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id DE13A2C93 for ; Wed, 1 Apr 2020 16:12:46 +0000 (UTC) X-FDA: 76659779532.28.women86_52743b443280b X-HE-Tag: women86_52743b443280b X-Filterd-Recvd-Size: 5258 Received: from mail-wr1-f66.google.com (mail-wr1-f66.google.com [209.85.221.66]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Wed, 1 Apr 2020 16:12:46 +0000 (UTC) Received: by mail-wr1-f66.google.com with SMTP id j17so673595wru.13 for ; Wed, 01 Apr 2020 09:12:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=8HOz2zhkw4iljGmp422o1/l5fbhE5jqc02RjkyFJxQo=; b=ZroYUg8RSsbFzAmRyrxh+ySIHobh3qgvqO89U5t1iYvvQFHhJGpGeQmQ/Ij7XKGlvN 8yGDA9AMxPErZYp41ng2iMzOzVbw03DUDBNh/NCu8tE4VxR09BT6GHCoPHinKFmlxxAH As8r72avAe/I71CSTj9p55ZW7TIp+wV7RHkFadEO6eB7K4S8oTpzCoLEh7IgNM5s9bM1 Qm8YtlgKDpsSwFkExjnf/MQSCnPaU9jpDx1npiCqQBlmluubFuX3p0eYF9qyTB85OrKa 4tDwfI9OdVkX9VLnxiIyzwaMXa2dWAwRi3uolQ5+4tgPk3MQQnJp0hOAxLmE3VxBhRi9 /kOA== X-Gm-Message-State: ANhLgQ3d4PoBw8Bc8Lso1oPLrvZrPNkQBgzI+q9i+b8m2t3HdgIWcxmg NKshMwu83pMAjaMstq+srsE= X-Google-Smtp-Source: ADFU+vt1zKgJs9RiwLMbYZioJpRWOvDXIbqrS9E36qARyrIIrNdJHMbJaJA/cmZ5Cyqg6uzTkfQldg== X-Received: by 2002:adf:f304:: with SMTP id i4mr25183059wro.46.1585757565470; Wed, 01 Apr 2020 09:12:45 -0700 (PDT) Received: from localhost (ip-37-188-180-223.eurotel.cz. [37.188.180.223]) by smtp.gmail.com with ESMTPSA id g128sm3267892wmf.27.2020.04.01.09.12.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2020 09:12:44 -0700 (PDT) Date: Wed, 1 Apr 2020 18:12:43 +0200 From: Michal Hocko To: Daniel Jordan Cc: David Hildenbrand , Shile Zhang , Andrew Morton , Kirill Tkhai , Pavel Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init Message-ID: <20200401161243.GW22681@dhcp22.suse.cz> References: <20200311123848.118638-1-shile.zhang@linux.alibaba.com> <20200401154217.GQ22681@dhcp22.suse.cz> <20200401160048.GU22681@dhcp22.suse.cz> <20200401160929.jwekhr24tb44odea@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401160929.jwekhr24tb44odea@ca-dmjordan1.us.oracle.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 01-04-20 12:09:29, Daniel Jordan wrote: > On Wed, Apr 01, 2020 at 06:00:48PM +0200, Michal Hocko wrote: > > On Wed 01-04-20 17:50:22, David Hildenbrand wrote: > > > On 01.04.20 17:42, Michal Hocko wrote: > > > > I am sorry but I have completely missed this patch. > > > > > > > > On Wed 11-03-20 20:38:48, Shile Zhang wrote: > > > >> When 'CONFIG_DEFERRED_STRUCT_PAGE_INIT' is set, 'pgdatinit' kthread will > > > >> initialise the deferred pages with local interrupts disabled. It is > > > >> introduced by commit 3a2d7fa8a3d5 ("mm: disable interrupts while > > > >> initializing deferred pages"). > > > >> > > > >> On machine with NCPUS <= 2, the 'pgdatinit' kthread could be bound to > > > >> the boot CPU, which could caused the tick timer long time stall, system > > > >> jiffies not be updated in time. > > > >> > > > >> The dmesg shown that: > > > >> > > > >> [ 0.197975] node 0 initialised, 32170688 pages in 1ms > > > >> > > > >> Obviously, 1ms is unreasonable. > > > >> > > > >> Now, fix it by restore in the pending interrupts for every 32*1204 pages > > > >> (128MB) initialized, give the chance to update the systemd jiffies. > > > >> The reasonable demsg shown likes: > > > >> > > > >> [ 1.069306] node 0 initialised, 32203456 pages in 894ms > > > >> > > > >> Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages"). > > > > > > > > I dislike this solution TBH. It effectivelly conserves the current code > > > > and just works around the problem. Why do we hold the IRQ lock here in > > > > the first place? This is an early init code and a very limited code is > > > > running at this stage. Certainly nothing memory hotplug related which > > > > should be the only path really interested in the resize lock AFAIR. > > > > > > Yeah, I don't think ACPI and friends are up yet. > > > > Just to save somebody time to check. The deferred initialization blocks > > the further boot until all workders are done - see page_alloc_init_late > > (kernel_init path). > > Ha, I just finished following all the hotplug paths to check this out, and as > you all know there are a *lot* :-) Well at least we're in agreement. Good to have it double checked! > > > > This needs a double checking but I strongly believe that the lock can be > > > > simply dropped in this path. > > This is what my fix does, it limits the time the resize lock is held. Just remove it from the deferred intialization and add a comment that we deliberately not taking the lock here because abc -- Michal Hocko SUSE Labs