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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 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable 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: 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