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[209.132.183.28]) by mx.google.com with ESMTPS id p15si18367417qvj.11.2019.07.26.02.37.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Jul 2019 02:37:11 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3F0B030C133A; Fri, 26 Jul 2019 09:37:10 +0000 (UTC) Received: from [10.36.116.244] (ovpn-116-244.ams2.redhat.com [10.36.116.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2703E600C4; Fri, 26 Jul 2019 09:37:07 +0000 (UTC) Subject: Re: [PATCH v3 1/5] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY To: Oscar Salvador Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, pasha.tatashin@soleen.com, mhocko@suse.com, anshuman.khandual@arm.com, Jonathan.Cameron@huawei.com, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190725160207.19579-1-osalvador@suse.de> <20190725160207.19579-2-osalvador@suse.de> <8b60e40a-1e8a-1f7c-a31d-ad2e511decd5@redhat.com> <20190726092959.GB26268@linux> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190726092959.GB26268@linux> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Fri, 26 Jul 2019 09:37:10 +0000 (UTC) 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: >> >>> >>> or >>> add_memory(0x1000, size_memory_block * 3); >>> >>> [memblock #0 ] >>> [0 - 1533 pfns ] - vmemmap for section#{0-2} >>> [1534 - 98304 pfns] - normal memory >>> >>> When using larger memory blocks (1GB or 2GB), the principle is the same. >>> >>> Of course, per whole-range granularity is nicer when it comes to have a large >>> contigous area, while per memory-block granularity allows us to have flexibility >>> when removing the memory. >> >> E.g., in my virtio-mem I am currently adding all memory blocks >> separately either way (to guranatee that remove_memory() works cleanly - >> see __release_memory_resource()), and to control the amount of >> not-offlined memory blocks (e.g., to make user space is actually >> onlining them). As it's just a prototype, this might change of course in >> the future. > > What is virtio-mem for? Did it that raised from a need? > Is it something you could try this patch on? virtio-mem is a paravirtualized way of hotplugging/removing to/from a guest. (similar to, but different to e.g., the hv-balloon). It adds/removes memory to/from the system. In the long term, it will try to also act similar-but different to a balloon - but that will require more work. In the first shot, it's all about adding/removing memory in the smaller granularity possible. The old prototype was https://lwn.net/Articles/755423/ Since then, a lot changed. Some more updated information is at https://events.linuxfoundation.org/wp-content/uploads/2017/12/virtio-mem-Paravirtualized-Memory-David-Hildenbrand-Red-Hat-1.pdf There is also a recording of the presentation on youtube. The current prototype is unfortunately not in a state yet that allows me to test with this patch set - my Master's thesis consumed most of my energy during the last year. I just started hacking on it again. -- Thanks, David / dhildenb