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Wed, 08 Jul 2020 12:10:26 -0400 X-MC-Unique: wliXH6sQNMGgSvnM9fu2KQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 07872107ACF7; Wed, 8 Jul 2020 16:10:24 +0000 (UTC) Received: from [10.36.113.117] (ovpn-113-117.ams2.redhat.com [10.36.113.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id ED16A1001925; Wed, 8 Jul 2020 16:10:19 +0000 (UTC) Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL To: Dan Williams Cc: Mike Rapoport , Mike Rapoport , Michal Hocko , Jia He , Catalin Marinas , Will Deacon , Vishal Verma , Dave Jiang , Andrew Morton , Baoquan He , Chuhong Yuan , Linux ARM , Linux Kernel Mailing List , Linux MM , linux-nvdimm , Kaly Xin References: <20200707180043.GA386073@linux.ibm.com> <20200708052626.GB386073@linux.ibm.com> <9a009cf6-6c30-91ca-a1a5-9aa090c66631@redhat.com> <999ea296-4695-1219-6a4d-a027718f61e5@redhat.com> <20200708083951.GH386073@linux.ibm.com> <20200708091520.GE128651@kernel.org> <20200708094549.GA781326@linux.ibm.com> <98166184-3aaf-479e-bfb3-fc737f4ac98d@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Rspamd-Queue-Id: 21F826C05 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 08.07.20 17:50, Dan Williams wrote: > On Wed, Jul 8, 2020 at 3:04 AM David Hildenbrand wrote: >> >> On 08.07.20 11:45, Mike Rapoport wrote: >>> On Wed, Jul 08, 2020 at 11:25:36AM +0200, David Hildenbrand wrote: >>>> On 08.07.20 11:15, Mike Rapoport wrote: >>>>>>>>>> >>>>>>> But on more theoretical/fundmanetal level, I think we lack a generic >>>>>>> abstraction similar to e.g. x86 'struct numa_meminfo' that serves as >>>>>>> translaton of firmware supplied information into data that can be used >>>>>>> by the generic mm without need to reimplement it for each and every >>>>>>> arch. >>>>>> >>>>>> Right. As I expressed, I am not a friend of using memblock for that, and >>>>>> the pgdat node span is tricky. >>>>>> >>>>>> Maybe abstracting that x86 concept is possible in some way (and we could >>>>>> restrict the information to boot-time properties, so we don't have to >>>>>> mess with memory hot(un)plug - just as done for numa_meminfo AFAIKS). >>>>> >>>>> I agree with pgdat part and disagree about memblock. It already has >>>>> non-init physmap, why won't we add memblock.memory to the mix? ;-) >>>> >>>> Can we generalize and tweak physmap to contain node info? That's all we >>>> need, no? (the special mem= parameter handling should not matter for our >>>> use case, where "physmap" and "memory" would differ) >>> >>> TBH, I have only random vague thoughts at the moment. This might be an >>> option. But then we need to enable physmap on !s390, right? >> >> Yes, looks like it. >> >>> >>>>> Now, seriously, memblock already has all the necessary information about >>>>> the coldplug memory for several architectures. x86 being an exception >>>>> because for some reason the reserved memory is not considered memory >>>>> there. The infrastructure for quiering and iterating memory regions is >>>>> already there. We just need to leave out the irrelevant parts, like >>>>> memblock.reserved and allocation funcions. >>>> >>>> I *really* don't want to mess with memblocks on memory hot(un)plug on >>>> x86 and s390x (+other architectures in the future). I also thought about >>>> stopping to create memblocks for hotplugged memory on arm64, by tweaking >>>> pfn_valid() to query memblocks only for early sections. >>>> >>>> If "physmem" is not an option, can we at least introduce something like >>>> ARCH_UPDTAE_MEMBLOCK_ON_HOTPLUG to avoid doing that on x86 and s390x for >>>> now (and later maybe for others)? >>> >>> I have to do more memory hotplug howework to answer that ;-) >>> >>> My general point is that we don't have to reinvent the wheel to have >>> coldplug memory representation, it's already there. We just need a way >>> to use it properly. >> >> Yes, I tend to agree. Details to be clarified :) > > I'm not quite understanding the concern, or requirement about > "updating memblock" in the hotplug path. The routines > memory_add_physaddr_to_nid() and phys_to_target_node() are helpers to > interrogate platform-firmware numa info through a common abstraction. > They place no burden on the memory hotplug code they're just used to > see if a hot-added range lies within an existing node span when > platform-firmware otherwise fails to communicate a node. x86 can > continue to back those helpers with numa_meminfo, arm64 can use a > generic memblock implementation and other archs can follow the arm64 > example if they want better numa answers for drivers. > See memblock_add_node()/memblock_remove() in mm/memory_hotplug.c. I don't want that code be reactivated for x86/s390x. That's all I am saying. -- Thanks, David / dhildenb