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[195.135.220.15]) by mx.google.com with ESMTPS id v30si9743725ejk.208.2019.07.25.02.40.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jul 2019 02:40:37 -0700 (PDT) Received-SPF: pass (google.com: domain of osalvador@suse.de designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of osalvador@suse.de designates 195.135.220.15 as permitted sender) smtp.mailfrom=osalvador@suse.de 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 5B419ABE9; Thu, 25 Jul 2019 09:40:37 +0000 (UTC) Date: Thu, 25 Jul 2019 11:40:34 +0200 From: Oscar Salvador To: David Hildenbrand Cc: Dan Williams , Andrew Morton , Michal Hocko , Pavel Tatashin , Jonathan Cameron , Anshuman Khandual , Vlastimil Babka , Linux MM , Linux Kernel Mailing List Subject: Re: [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS Message-ID: <20190725094030.GA16069@linux> References: <20190625075227.15193-1-osalvador@suse.de> <20190625075227.15193-3-osalvador@suse.de> <20190725092751.GA15964@linux> <71a30086-b093-48a4-389f-7e407898718f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <71a30086-b093-48a4-389f-7e407898718f@redhat.com> 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 Thu, Jul 25, 2019 at 11:30:23AM +0200, David Hildenbrand wrote: > On 25.07.19 11:27, Oscar Salvador wrote: > > On Wed, Jul 24, 2019 at 01:11:52PM -0700, Dan Williams wrote: > >> On Tue, Jun 25, 2019 at 12:53 AM Oscar Salvador wrote: > >>> > >>> This patch introduces MHP_MEMMAP_DEVICE and MHP_MEMMAP_MEMBLOCK flags, > >>> and prepares the callers that add memory to take a "flags" parameter. > >>> This "flags" parameter will be evaluated later on in Patch#3 > >>> to init mhp_restrictions struct. > >>> > >>> The callers are: > >>> > >>> add_memory > >>> __add_memory > >>> add_memory_resource > >>> > >>> Unfortunately, we do not have a single entry point to add memory, as depending > >>> on the requisites of the caller, they want to hook up in different places, > >>> (e.g: Xen reserve_additional_memory()), so we have to spread the parameter > >>> in the three callers. > >>> > >>> The flags are either MHP_MEMMAP_DEVICE or MHP_MEMMAP_MEMBLOCK, and only differ > >>> in the way they allocate vmemmap pages within the memory blocks. > >>> > >>> MHP_MEMMAP_MEMBLOCK: > >>> - With this flag, we will allocate vmemmap pages in each memory block. > >>> This means that if we hot-add a range that spans multiple memory blocks, > >>> we will use the beginning of each memory block for the vmemmap pages. > >>> This strategy is good for cases where the caller wants the flexiblity > >>> to hot-remove memory in a different granularity than when it was added. > >>> > >>> E.g: > >>> We allocate a range (x,y], that spans 3 memory blocks, and given > >>> memory block size = 128MB. > >>> [memblock#0 ] > >>> [0 - 511 pfns ] - vmemmaps for section#0 > >>> [512 - 32767 pfns ] - normal memory > >>> > >>> [memblock#1 ] > >>> [32768 - 33279 pfns] - vmemmaps for section#1 > >>> [33280 - 65535 pfns] - normal memory > >>> > >>> [memblock#2 ] > >>> [65536 - 66047 pfns] - vmemmap for section#2 > >>> [66048 - 98304 pfns] - normal memory > >>> > >>> MHP_MEMMAP_DEVICE: > >>> - With this flag, we will store all vmemmap pages at the beginning of > >>> hot-added memory. > >>> > >>> E.g: > >>> We allocate a range (x,y], that spans 3 memory blocks, and given > >>> memory block size = 128MB. > >>> [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, MHP_MEMMAP_DEVICE is nicer when it comes to have a large contigous > >>> area, while MHP_MEMMAP_MEMBLOCK allows us to have flexibility when removing the > >>> memory. > >> > >> Concept and patch looks good to me, but I don't quite like the > >> proliferation of the _DEVICE naming, in theory it need not necessarily > >> be ZONE_DEVICE that is the only user of that flag. I also think it > >> might be useful to assign a flag for the default 'allocate from RAM' > >> case, just so the code is explicit. So, how about: > > > > Well, MHP_MEMMAP_DEVICE is not tied to ZONE_DEVICE. > > MHP_MEMMAP_DEVICE was chosen to make a difference between: > > > > * allocate memmap pages for the whole memory-device > > * allocate memmap pages on each memoryblock that this memory-device spans > > I agree that DEVICE is misleading here, you are assuming a one-to-one > mapping between a device and add_memory(). You are actually taliing > about "allocate a single chunk of mmap pages for the whole memory range > that is added - which could consist of multiple memory blocks". Well, I could not come up with a better name. MHP_MEMMAP_ALL? MHP_MEMMAP_WHOLE? I will send v3 shortly and then we can think of a better name. > > -- > > Thanks, > > David / dhildenb > -- Oscar Salvador SUSE L3