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[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-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@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 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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 AD7FBC5ACD6 for ; Wed, 18 Mar 2020 15:13:17 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6153520757 for ; Wed, 18 Mar 2020 15:13:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SdmhbB/e" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6153520757 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48jD7Y0bzpzDqy9 for ; Thu, 19 Mar 2020 02:13:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=63.128.21.74; helo=us-smtp-delivery-74.mimecast.com; envelope-from=vkuznets@redhat.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=SdmhbB/e; dkim-atps=neutral Received: from us-smtp-delivery-74.mimecast.com (us-smtp-delivery-74.mimecast.com [63.128.21.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48jCrp702ZzDqll for ; Thu, 19 Mar 2020 02:00:26 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584543622; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eGl81AXOETQ2vk6QwAuLbQxuIwytBmzR9QEu1doc/+g=; b=SdmhbB/eaYT3jfHpGK+gATxl5tmSXiXxd0HoRrQyePgkwDns3ojRboNhFxtXCgpYz1h2ed aLQQZ9S7F5YwbRSGzBSM4kXGc6CdXEjh0FAjhKBNctqASjLPxdCch6JgFZQETHXYBfu5fJ QBUTIsZ1rjlGd1nbnPw4RwuQcJkVQfg= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-366-xyCtUB_PMSO-ezDabvmaqQ-1; Wed, 18 Mar 2020 11:00:20 -0400 X-MC-Unique: xyCtUB_PMSO-ezDabvmaqQ-1 Received: by mail-wr1-f69.google.com with SMTP id o9so12488039wrw.14 for ; Wed, 18 Mar 2020 08:00:20 -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=VE/ZHjwJgk7dzj56K7CmZRu1i42ObFzWrjvqF9rmGord5xtkWyW2Yhmab5P+hcFJc6 bpyGR3YDaS0ibKYukJM2LChHW7HYopyfWTptzjUDYpJFicwE6zG0a4vA/2/Ta/i8TX6C GcZSSoeMNQPlbPQktkYDAas/MaJHxbpm9L7PZ5qwGt/431riJgILzKxEThX0v4mgKmYK u/FACtpnjd2fHr5w/GXUEDpMYNfLVN2OWWcSVVZugyHNLcOaSpIOEUP2cFnNpLN8+FFz uQtihev50xLjzJpB0Q8Xi9U8QnGtayJspODA3O6HKxqg5Zfjh3L5XoyDwaRZeYXyPxW9 l9tQ== X-Gm-Message-State: ANhLgQ3ATBHMKiHYaq5+sXEC4d3vW3NH9Rp45TVPrXfsb+1gfJtpM+tx o1jLJ8COGtMhVfwSWHy12sAud4jPMYDptX8pr5vPThIY93WeGLRPHtkoUOv1mtjVQxqijiirQPe KAO0ZI4RGCp3vnXjqPwucD7GwlA== X-Received: by 2002:a5d:474c:: with SMTP id o12mr6171291wrs.156.1584543618829; 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 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 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yumei Huang , linux-hyperv@vger.kernel.org, Michal Hocko , David Hildenbrand , Michal Hocko , linux-mm@kvack.org, Paul Mackerras , "K. Y. Srinivasan" , Wei Liu , Stephen Hemminger , "Rafael J. Wysocki" , Eduardo Habkost , Haiyang Zhang , Wei Yang , Oscar Salvador , Milan Zamazal , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Igor Mammedov , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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. --=20 Vitaly