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[2003:cb:c73d:de00:7cf7:9482:e5dc:6ad0]) by smtp.gmail.com with ESMTPSA id t6-20020a05600c198600b0040e48abec33sm1722288wmq.45.2024.01.10.02.42.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jan 2024 02:42:32 -0800 (PST) Message-ID: Date: Wed, 10 Jan 2024 11:42:31 +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: Ryan Roberts , Barry Song <21cnbao@gmail.com> 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: <68d5ce7e-6587-47c6-bd0f-988adf5d92a4@arm.com> 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-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: EBE4D140005 X-Stat-Signature: zi4ut6kzz7jew7rn6m6sudd1aemg9qqo X-HE-Tag: 1704883358-88246 X-HE-Meta: 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 BThxxqIV 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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 11:38, 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. Oh no. Let's not make everything more complicated for the purpose of some stats. -- Cheers, David / dhildenb