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Wed, 8 Jul 2020 08:26:46 +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 D41282B4C2; Wed, 8 Jul 2020 08:26:42 +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 , 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: <20200707055917.143653-1-justin.he@arm.com> <20200707055917.143653-2-justin.he@arm.com> <20200707115454.GN5913@dhcp22.suse.cz> <20200707121302.GB9411@linux.ibm.com> <474f93e7-c709-1a13-5418-29f1777f614c@redhat.com> <20200707180043.GA386073@linux.ibm.com> <20200708052626.GB386073@linux.ibm.com> <9a009cf6-6c30-91ca-a1a5-9aa090c66631@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <999ea296-4695-1219-6a4d-a027718f61e5@redhat.com> Date: Wed, 8 Jul 2020 10:26:41 +0200 User-Agent: Mozilla/5.0 (X11; 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: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.07.20 09:50, Dan Williams wrote: > On Wed, Jul 8, 2020 at 12:22 AM David Hildenbrand wrote: >> >> On 08.07.20 07:27, Mike Rapoport wrote: >>> On Tue, Jul 07, 2020 at 03:05:48PM -0700, Dan Williams wrote: >>>> On Tue, Jul 7, 2020 at 11:01 AM Mike Rapoport wrote: >>>>> >>>>> On Tue, Jul 07, 2020 at 02:26:08PM +0200, David Hildenbrand wrote: >>>>>> On 07.07.20 14:13, Mike Rapoport wrote: >>>>>>> On Tue, Jul 07, 2020 at 01:54:54PM +0200, Michal Hocko wrote: >>>>>>>> On Tue 07-07-20 13:59:15, Jia He wrote: >>>>>>>>> This exports memory_add_physaddr_to_nid() for module driver to use. >>>>>>>>> >>>>>>>>> memory_add_physaddr_to_nid() is a fallback option to get the nid in case >>>>>>>>> NUMA_NO_NID is detected. >>>>>>>>> >>>>>>>>> Suggested-by: David Hildenbrand >>>>>>>>> Signed-off-by: Jia He >>>>>>>>> --- >>>>>>>>> arch/arm64/mm/numa.c | 5 +++-- >>>>>>>>> 1 file changed, 3 insertions(+), 2 deletions(-) >>>>>>>>> >>>>>>>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c >>>>>>>>> index aafcee3e3f7e..7eeb31740248 100644 >>>>>>>>> --- a/arch/arm64/mm/numa.c >>>>>>>>> +++ b/arch/arm64/mm/numa.c >>>>>>>>> @@ -464,10 +464,11 @@ void __init arm64_numa_init(void) >>>>>>>>> >>>>>>>>> /* >>>>>>>>> * We hope that we will be hotplugging memory on nodes we already know about, >>>>>>>>> - * such that acpi_get_node() succeeds and we never fall back to this... >>>>>>>>> + * such that acpi_get_node() succeeds. But when SRAT is not present, the node >>>>>>>>> + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option. >>>>>>>>> */ >>>>>>>>> int memory_add_physaddr_to_nid(u64 addr) >>>>>>>>> { >>>>>>>>> - pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr); >>>>>>>>> return 0; >>>>>>>>> } >>>>>>>>> +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid); >>>>>>>> >>>>>>>> Does it make sense to export a noop function? Wouldn't make more sense >>>>>>>> to simply make it static inline somewhere in a header? I haven't checked >>>>>>>> whether there is an easy way to do that sanely bu this just hit my eyes. >>>>>>> >>>>>>> We'll need to either add a CONFIG_ option or arch specific callback to >>>>>>> make both non-empty (x86, powerpc, ia64) and empty (arm64, sh) >>>>>>> implementations coexist ... >>>>>> >>>>>> Note: I have a similar dummy (return 0) patch for s390x lying around here. >>>>> >>>>> Then we'll call it a tie - 3:3 ;-) >>>> >>>> So I'd be happy to jump on the train of people wanting to export the >>>> ARM stub for this (and add a new ARM stub for phys_to_target_node()), >>>> but Will did have a plausibly better idea that I have been meaning to >>>> circle back to: >>>> >>>> http://lore.kernel.org/r/20200325111039.GA32109@willie-the-truck >>>> >>>> ...i.e. iterate over node data to do the lookup. This would seem to >>>> work generically for multiple archs unless I am missing something? >> >> IIRC, only memory assigned to/onlined to a ZONE is represented in the >> pgdat node span. E.g., not offline memory blocks. > > So this dovetails somewhat with Will's idea. What if we populated > node_data for "offline" ranges? I started there, but then saw > ARCH_KEEP_MEMBLOCK and thought it would be safer to just teach > phys_to_target_node() to use that rather than update other code paths > to expect node_data might not always reflect online data. We currently need a somewhat-accurate pgdat node span to detect when to offline a node. See try_offline_node(). This works fairly reliable. Shrinking the node span is currently fairly easy for !ZONE_DEVICE memory, because we can rely on pfn_to_online_page() + pfn_to_nid(pfn). See e.g., find_biggest_section_pfn(). If we glue growing/shrinking the node span to adding/removing of memory (instead of e.g., onlining/offlining), we can no longer base shrinking on memmap data. We would have to get the information ("how far can I shrink the node span, is it empty?") from somewhere else. E.g., for_each_memory_block() - but that one does not cover ZONE_DEVICE. And there are memory blocks which cover multiple nodes, in which case we only store one of them ... unreliable. This certainly needs more thought :/ > >> Esp., when hotplugging + onlining consecutive memory, there won't really >> be any intersections in most cases if I am not wrong. It would not be >> "intersection" but rather "closest fit". >> >> With overlapping nodes it's even more unclear. Which one to pick? > > In the overlap case you get what you get. Some signal is better than > the noise of a dummy function. The consequences of picking the wrong > node might be that the kernel can't properly associate a memory range > to its performance data tables in firmware, but then again firmware > messed up with an overlapping node definition in the first instance. I'd be curious if what we are trying to optimize here is actually worth optimizing. IOW, is there a well-known scenario where the dummy value on arm64 would be problematic and is worth the effort? I mean, in all performance relevant setups (ignoring hv_balloon/xen-balloon/prove_store(), which also use memory_add_physaddr_to_nid()), we should have a proper PXM/node specified by the hardware on memory hotadd. The fallback of memory_add_physaddr_to_nid() is not relevant in these scenarios. -- Thanks, David / dhildenb