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[209.132.183.28]) by mx.google.com with ESMTPS id e14si2328089qtg.209.2019.04.05.03.56.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Apr 2019 03:56:57 -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 883AF307D8E3; Fri, 5 Apr 2019 10:56:56 +0000 (UTC) Received: from [10.36.117.47] (ovpn-117-47.ams2.redhat.com [10.36.117.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2287560491; Fri, 5 Apr 2019 10:56:54 +0000 (UTC) Subject: Re: [PATCH 2/2] mm, memory_hotplug: provide a more generic restrictions for memory hotplug To: Michal Hocko Cc: Oscar Salvador , akpm@linux-foundation.org, dan.j.williams@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20190404125916.10215-1-osalvador@suse.de> <20190404125916.10215-3-osalvador@suse.de> <880c5d09-7d4e-2a97-e826-a8a6572216b2@redhat.com> <20190404180144.lgpf6qgnp67ib5s7@d104.suse.de> <5f735328-3451-ebd7-048e-e83e74e2c622@redhat.com> <20190405071418.GN12864@dhcp22.suse.cz> <20190405103053.GO12864@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/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190405103053.GO12864@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 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Fri, 05 Apr 2019 10:56:56 +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: On 05.04.19 12:30, Michal Hocko wrote: > On Fri 05-04-19 10:05:09, David Hildenbrand wrote: >> On 05.04.19 09:14, Michal Hocko wrote: >>> On Thu 04-04-19 20:27:41, David Hildenbrand wrote: >>>> On 04.04.19 20:01, Oscar Salvador wrote: >>> [...] >>>>> But I am not really convinced by MHP_SYSTEM_RAM name, and I think we should stick >>>>> with MHP_MEMBLOCK_API because it represents __what__ is that flag about and its >>>>> function, e.g: create memory block devices. >>> >>> Exactly >> >> Fine with me for keeping what Oscar has. >> >>> >>>> This nicely aligns with the sub-section memory add support discussion. >>>> >>>> MHP_MEMBLOCK_API immediately implies that >>>> >>>> - memory is used as system ram. Memory can be onlined/offlined. Markers >>>> at sections indicate if the section is online/offline. >>> >>> No there is no implication like that. It means only that the onlined >>> memory has a sysfs interface. Nothing more, nothing less >> >> As soon as there is a online/offline interface, you *can* (and user >> space usually *will*) online that memory. Onlining/offlining is only >> defined for memory to be added to the buddy - memory to be used as >> "system ram". Doing it for random device memory will not work / result >> in undefined behavior. > > No, not really. We really do not care where the memory comes from. Is it > RAM, NVDIMM, $FOO_BAR_OF_A_FUTURE_BUZZ. We only do care that the memory > can be onlined - user triggered associated with a zone. The memory even > doesn't have to go to the page allocator. > Yes, true, I was rather meaning if the caller wants ZONE_DEVICE, memory block devices are never an option. So "how the memory is used" not "where memory comes from". add_memory() vs. devm_memremap_pages(). -- Thanks, David / dhildenb