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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 C9756C5ACD6 for ; Wed, 18 Mar 2020 15:00:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A272B20757 for ; Wed, 18 Mar 2020 15:00:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FWcITW8h" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726789AbgCRPAX (ORCPT ); Wed, 18 Mar 2020 11:00:23 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:59088 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726726AbgCRPAX (ORCPT ); Wed, 18 Mar 2020 11:00:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584543621; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vM5m3AgHzQ8TLHWUI0zWYeLWIk49n7q4tlPXYDa1gEQ=; b=FWcITW8h9pdTlAORXzYB3p0IJSisHmFknF2lLYFTUKgXIEtdJfdUWnyj8ghbIj2+AG4UBc AD0fZW8/YSUZBiUnpUw1X0pMWeIMc5aEg0/7XI81AWpaQwCz1qn0kqFJ++Uc6DfJAdvl76 e2UYJ3id9J1YOilW7WfU/vFsRZVuS1k= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-75-inQ68xkTNmaFnsw9eEUiKw-1; Wed, 18 Mar 2020 11:00:19 -0400 X-MC-Unique: inQ68xkTNmaFnsw9eEUiKw-1 Received: by mail-wm1-f71.google.com with SMTP id r23so1201270wmn.3 for ; Wed, 18 Mar 2020 08:00:19 -0700 (PDT) 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:in-reply-to:references:date :message-id:mime-version; bh=vM5m3AgHzQ8TLHWUI0zWYeLWIk49n7q4tlPXYDa1gEQ=; b=lT8xCW2NJLTqEUBccJ/anoPJKUYeTl5G1QvKWldwiUnHViLC6zwCNbL6L0rRDngntZ NEVm11jyxAlsIoE4uDMMvl0ShcsCCaf4/P5S6r6M4o8C52L1AYczbj8esSy+gcsJqvSe XzTS5pVr2R3oU7eS+uezqQcumoUvdCmhSPox2EwN9yxeRvLe96pVud8c4WkR4nMkBfwF Mqm5DP/QCaoJRy0FJdqcYdfI2dv0yy3GcWJixryA4SsOBPyOYdCZvbSsFwt/amsMgSDz F5bXuOdZYiurttb9zIfB6+4ekIR8kVuUMGyuxQUpKEtuYmAZEUZ97RB5MEsws0+PiIWc Ay8Q== X-Gm-Message-State: ANhLgQ2p9vD2eXz5RW2hf0ljDhgi+0rmJAKbKsJu085fhs71t6k8SBfe a2r8kCIPgyWXiEA0mmWWidpksUa5e1oN/eii0RkMGX2Ow87/HDVdVkJnVDAC5bTq+2lcLzEZAmn nCK2Xv8zr5A+pkMrY49G269M7 X-Received: by 2002:a5d:474c:: with SMTP id o12mr6171258wrs.156.1584543618597; Wed, 18 Mar 2020 08:00:18 -0700 (PDT) X-Google-Smtp-Source: ADFU+vv+zT1QJmX75ZvxUY39VsKhPCv6bUGTeJatv+Ce8GRjcg/v0Lus2RekaAdHVMZwveqCGhi86Q== X-Received: by 2002:a5d:474c:: with SMTP id o12mr6171235wrs.156.1584543618411; Wed, 18 Mar 2020 08:00:18 -0700 (PDT) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id x13sm4631033wmj.5.2020.03.18.08.00.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2020 08:00:17 -0700 (PDT) From: Vitaly Kuznetsov To: Baoquan He Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-hyperv@vger.kernel.org, Yumei Huang , Igor Mammedov , Eduardo Habkost , Milan Zamazal , Andrew Morton , Benjamin Herrenschmidt , Greg Kroah-Hartman , Haiyang Zhang , "K. Y. Srinivasan" , Michael Ellerman , Michal Hocko , Michal Hocko , Oscar Salvador , Paul Mackerras , "Rafael J. Wysocki" , Stephen Hemminger , Wei Liu , Wei Yang Subject: Re: [PATCH v2 0/8] mm/memory_hotplug: allow to specify a default online_type In-Reply-To: <20200318144119.GD30899@MiWiFi-R3L-srv> References: <20200317104942.11178-1-david@redhat.com> <20200318130517.GC30899@MiWiFi-R3L-srv> <87d0993gto.fsf@vitty.brq.redhat.com> <20200318144119.GD30899@MiWiFi-R3L-srv> Date: Wed, 18 Mar 2020 16:00:15 +0100 Message-ID: <874kul3dz4.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Baoquan He writes: > Is there a reason hyperV need boot with small memory, then enlarge it > with huge memory? Since it's a real case in hyperV, I guess there must > be reason, I am just curious. > It doesn't really *need* to but this can be utilized in e.g. 'hot standby' schemes I believe. Also, it may be enough if the administrator is just trying to e.g. double the size of RAM but the VM is already under memory pressure. I wouldn't say that these cases are common but afair bugs like 'I tried adding more memory to my VM and it just OOMed' were reported in the past. -- Vitaly