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[2003:cb:c73d:de00:7cf7:9482:e5dc:6ad0]) by smtp.gmail.com with ESMTPSA id t21-20020a05600c451500b0040e3ac9f4c8sm1736178wmo.28.2024.01.10.02.54.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jan 2024 02:54:36 -0800 (PST) Message-ID: <714438db-b83b-41e7-bf73-b95267fa34c2@redhat.com> Date: Wed, 10 Jan 2024 11:54:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1] tools/mm: Add thpmaps script to dump THP usage info To: Barry Song <21cnbao@gmail.com>, Ryan Roberts Cc: John Hubbard , Andrew Morton , Zenghui Yu , Matthew Wilcox , Kefeng Wang , Zi Yan , Alistair Popple , linux-mm@kvack.org References: <20240102153828.1002295-1-ryan.roberts@arm.com> <4e7445a0-acc9-487f-999f-a2b6d03d265e@nvidia.com> <3bd5e4a3-9f67-4483-9a0e-9abb5eb783cd@arm.com> <94ebe62b-5f55-4be9-b464-4105b4692496@arm.com> <68d5ce7e-6587-47c6-bd0f-988adf5d92a4@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: E6FBAC0022 X-Rspam-User: X-Stat-Signature: h53ibq55okpg7py7xhh6mn7eihf7axhe X-Rspamd-Server: rspam01 X-HE-Tag: 1704884080-644210 X-HE-Meta: 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 RiIwUx3t 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 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: List-Subscribe: List-Unsubscribe: On 10.01.24 11:48, Barry Song wrote: > On Wed, Jan 10, 2024 at 6:38 PM Ryan Roberts wrote: >> >> On 10/01/2024 10:30, Barry Song wrote: >>> On Wed, Jan 10, 2024 at 6:23 PM Ryan Roberts wrote: >>>> >>>> On 10/01/2024 09:09, Barry Song wrote: >>>>> On Wed, Jan 10, 2024 at 4:58 PM Ryan Roberts wrote: >>>>>> >>>>>> On 10/01/2024 08:02, Barry Song wrote: >>>>>>> On Wed, Jan 10, 2024 at 12:16 PM John Hubbard wrote: >>>>>>>> >>>>>>>> On 1/9/24 19:51, Barry Song wrote: >>>>>>>>> On Wed, Jan 10, 2024 at 11:35 AM John Hubbard wrote: >>>>>>>> ... >>>>>>>>>> Hi Ryan, >>>>>>>>>> >>>>>>>>>> One thing that immediately came up during some recent testing of mTHP >>>>>>>>>> on arm64: the pid requirement is sometimes a little awkward. I'm running >>>>>>>>>> tests on a machine at a time for now, inside various containers and >>>>>>>>>> such, and it would be nice if there were an easy way to get some numbers >>>>>>>>>> for the mTHPs across the whole machine. >>>>>> >>>>>> Just to confirm, you're expecting these "global" stats be truely global and not >>>>>> per-container? (asking because you exploicitly mentioned being in a container). >>>>>> If you want per-container, then you can probably just create the container in a >>>>>> cgroup? >>>>>> >>>>>>>>>> >>>>>>>>>> I'm not sure if that changes anything about thpmaps here. Probably >>>>>>>>>> this is fine as-is. But I wanted to give some initial reactions from >>>>>>>>>> just some quick runs: the global state would be convenient. >>>>>> >>>>>> Thanks for taking this for a spin! Appreciate the feedback. >>>>>> >>>>>>>>> >>>>>>>>> +1. but this seems to be impossible by scanning pagemap? >>>>>>>>> so may we add this statistics information in kernel just like >>>>>>>>> /proc/meminfo or a separate /proc/mthp_info? >>>>>>>>> >>>>>>>> >>>>>>>> Yes. From my perspective, it looks like the global stats are more useful >>>>>>>> initially, and the more detailed per-pid or per-cgroup stats are the >>>>>>>> next level of investigation. So feels odd to start with the more >>>>>>>> detailed stats. >>>>>>>> >>>>>>> >>>>>>> probably because this can be done without the modification of the kernel. >>>>>> >>>>>> Yes indeed, as John said in an earlier thread, my previous attempts to add stats >>>>>> directly in the kernel got pushback; DavidH was concerned that we don't really >>>>>> know exectly how to account mTHPs yet >>>>>> (whole/partial/aligned/unaligned/per-size/etc) so didn't want to end up adding >>>>>> the wrong ABI and having to maintain it forever. There has also been some >>>>>> pushback regarding adding more values to multi-value files in sysfs, so David >>>>>> was suggesting coming up with a whole new scheme at some point (I know >>>>>> /proc/meminfo isn't sysfs, but the equivalent files for NUMA nodes and cgroups >>>>>> do live in sysfs). >>>>>> >>>>>> Anyway, this script was my attempt to 1) provide a short term solution to the >>>>>> "we need some stats" request and 2) provide a context in which to explore what >>>>>> the right stats are - this script can evolve without the ABI problem. >>>>>> >>>>>>> The detailed per-pid or per-cgroup is still quite useful to my case in which >>>>>>> we set mTHP enabled/disabled and allowed sizes according to vma types, >>>>>>> eg. libc_malloc, java heaps etc. >>>>>>> >>>>>>> Different vma types can have different anon_name. So I can use the detailed >>>>>>> info to find out if specific VMAs have gotten mTHP properly and how many >>>>>>> they have gotten. >>>>>>> >>>>>>>> However, Ryan did clearly say, above, "In future we may wish to >>>>>>>> introduce stats directly into the kernel (e.g. smaps or similar)". And >>>>>>>> earlier he ran into some pushback on trying to set up /proc or /sys >>>>>>>> values because this is still such an early feature. >>>>>>>> >>>>>>>> I wonder if we could put the global stats in debugfs for now? That's >>>>>>>> specifically supposed to be a "we promise *not* to keep this ABI stable" >>>>>>>> location. >>>>>> >>>>>> Now that I think about it, I wonder if we can add a --global mode to the script >>>>>> (or just infer global when neither --pid nor --cgroup are provided). I think I >>>>>> should be able to determine all the physical memory ranges from /proc/iomem, >>>>>> then grab all the info we need from /proc/kpageflags. We should then be able to >>>>>> process it all in much the same way as for --pid/--cgroup and provide the same >>>>>> stats, but it will apply globally. What do you think? >>>> >>>> Having now thought about this for a few mins (in the shower, if anyone wants the >>>> complete picture :) ), this won't quite work. This approach doesn't have the >>>> virtual mapping information so the best it can do is tell us "how many of each >>>> size of THP are allocated?" - it doesn't tell us anything about whether they are >>>> fully or partially mapped or what their alignment is (all necessary if we want >>>> to know if they are contpte-mapped). So I don't think this approach is going to >>>> be particularly useful. >>>> >>>> And this is also the big problem if we want to gather stats inside the kernel; >>>> if we want something equivalant to /proc/meminfo's >>>> AnonHugePages/ShmemPmdMapped/FilePmdMapped, we need to consider not just the >>>> allocation of the THP but also whether it is mapped. That's easy for >>>> PMD-mappings, because there is only one entry to consider - when you set it, you >>>> increment the number of PMD-mapped THPs, when you clear it, you decrement. But >>>> for PTE-mappings it's harder; you know the size when you are mapping so its easy >>>> to increment, but you can do a partial unmap, so you would need to scan the PTEs >>>> to figure out if we are unmapping the first page of a previously >>>> fully-PTE-mapped THP, which is expensive. We would need a cheap mechanism to >>>> determine "is this folio fully and contiguously mapped in at least one process?". >>> >>> as OPPO's approach I shared to you before is maintaining two mapcount >>> 1. entire map >>> 2. subpage's map >>> 3. if 1 and 2 both exist, it is DoubleMapped. >>> >>> This isn't a problem for us. and everytime if we do a partial unmap, >>> we have an explicit >>> cont_pte split which will decrease the entire map and increase the >>> subpage's mapcount. >>> >>> but its downside is that we expose this info to mm-core. >> >> OK, but I think we have a slightly more generic situation going on with the >> upstream; If I've understood correctly, you are using the PTE_CONT bit in the >> PTE to determne if its fully mapped? That works for your case where you only >> have 1 size of THP that you care about (contpte-size). But for the upstream, we >> have multi-size THP so we can't use the PTE_CONT bit to determine if its fully >> mapped because we can only use that bit if the THP is at least 64K and aligned, >> and only on arm64. We would need a SW bit for this purpose, and the mm would >> need to update that SW bit for every PTE one the full -> partial map transition. > > My current implementation does use cont_pte but i don't think it is a must-have. > we don't need a bit in PTE to know if we are partially unmapping a large folio > at all. > > as long as we are unmapping a part of a large folio, we do know what we are > doing. if a large folio is mapped entirely in a process, we get only > entire_map +1, > if we are unmapping a subpage of it, we get entire_map -1 and remained subpage's > mapcount + 1. if we are only mapping a part of this large folio, we > only increase > its subpages' mapcount. That doesn't work as soon as you unmap a second subpage. Not to mention that people ( :) ) are working on removing the subpage mapcounts. I'm going propose that as a topic for LSF/MM soon, once I get to it. -- Cheers, David / dhildenb