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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 31BA7C43441 for ; Wed, 14 Nov 2018 09:39:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0267D22419 for ; Wed, 14 Nov 2018 09:39:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0267D22419 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732612AbeKNTlg (ORCPT ); Wed, 14 Nov 2018 14:41:36 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49180 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727833AbeKNTlg (ORCPT ); Wed, 14 Nov 2018 14:41:36 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 31672C05D401; Wed, 14 Nov 2018 09:39:08 +0000 (UTC) Received: from [10.36.117.19] (ovpn-117-19.ams2.redhat.com [10.36.117.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id CE6B95D75F; Wed, 14 Nov 2018 09:39:06 +0000 (UTC) Subject: Re: Memory hotplug softlock issue To: Michal Hocko Cc: Baoquan He , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, aarcange@redhat.com References: <20181114070909.GB2653@MiWiFi-R3L-srv> <5a6c6d6b-ebcd-8bfa-d6e0-4312bfe86586@redhat.com> <20181114090134.GG23419@dhcp22.suse.cz> <4449a0a2-be72-02bb-9f02-ed2484b160f8@redhat.com> <20181114093720.GI23419@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181114093720.GI23419@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 14 Nov 2018 09:39:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> Failing on ENOMEM is a questionable thing. I haven't seen that happening >>> wildly but if it is a case then I wouldn't be opposed. >>> >>>> You mentioned memory pressure, if our host is under memory pressure we >>>> can easily trigger running into an endless loop there, because we >>>> basically ignore -ENOMEM e.g. when we cannot get a page to migrate some >>>> memory to be offlined. I assume this is the case here. >>>> do_migrate_range() could be the bad boy if it keeps failing forever and >>>> we keep retrying. >> >> I've seen quite some issues while playing with virtio-mem, but didn't >> have the time to look into the details. Still on my long list of things >> to look into. > > Memory hotplug is really far away from being optimal and robust. This > has always been the case. Issues used to be workaround by retry limits > etc. If we ever want to make it more robust we have to bite a bullet and > actually chase all the issues that might be basically anywhere and fix > them. This is just a nature of a pony that memory hotplug is. > Yes I agree, no more workarounds. -- Thanks, David / dhildenb