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[195.135.220.15]) by mx.google.com with ESMTPS id k51si23364534eda.111.2019.07.31.23.13.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 23:13:47 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C65CCACEF; Thu, 1 Aug 2019 06:13:46 +0000 (UTC) Date: Thu, 1 Aug 2019 08:13:44 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Pavel Tatashin , Dan Williams , Oscar Salvador Subject: Re: [PATCH v1] drivers/base/memory.c: Don't store end_section_nr in memory blocks Message-ID: <20190801061344.GA11627@dhcp22.suse.cz> References: <20190731122213.13392-1-david@redhat.com> <20190731124356.GL9330@dhcp22.suse.cz> <20190731132534.GQ9330@dhcp22.suse.cz> <58bd9479-051b-a13b-b6d0-c93aac2ed1b3@redhat.com> <20190731141411.GU9330@dhcp22.suse.cz> <20190731143714.GX9330@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed 31-07-19 16:43:58, David Hildenbrand wrote: > On 31.07.19 16:37, Michal Hocko wrote: > > On Wed 31-07-19 16:21:46, David Hildenbrand wrote: > > [...] > >>> Thinking about it some more, I believe that we can reasonably provide > >>> both APIs controlable by a command line parameter for backwards > >>> compatibility. It is the hotplug code to control sysfs APIs. E.g. > >>> create one sysfs entry per add_memory_resource for the new semantic. > >> > >> Yeah, but the real question is: who needs it. I can only think about > >> some DIMM scenarios (some, not all). I would be interested in more use > >> cases. Of course, to provide and maintain two APIs we need a good reason. > > > > Well, my 3TB machine that has 7 movable nodes could really go with less > > than > > $ find /sys/devices/system/memory -name "memory*" | wc -l > > 1729> > > The question is if it would be sufficient to increase the memory block > size even further for these kinds of systems (e.g., via a boot parameter > - I think we have that on uv systems) instead of having blocks of > different sizes. Say, 128GB blocks because you're not going to hotplug > 128MB DIMMs into such a system - at least that's my guess ;) The system has [ 0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x10000000000-0x17fffffffff] [ 0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x80000000000-0x87fffffffff] [ 0.000000] ACPI: SRAT: Node 3 PXM 3 [mem 0x90000000000-0x97fffffffff] [ 0.000000] ACPI: SRAT: Node 4 PXM 4 [mem 0x100000000000-0x107fffffffff] [ 0.000000] ACPI: SRAT: Node 5 PXM 5 [mem 0x110000000000-0x117fffffffff] [ 0.000000] ACPI: SRAT: Node 6 PXM 6 [mem 0x180000000000-0x183fffffffff] [ 0.000000] ACPI: SRAT: Node 7 PXM 7 [mem 0x190000000000-0x191fffffffff] hotplugable memory. I would love to have those 7 memory blocks to work with. Any smaller grained split is just not helping as the platform will not be able to hotremove it anyway. -- Michal Hocko SUSE Labs