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[91.12.102.223]) by smtp.gmail.com with ESMTPSA id o5-20020a05600c510500b0040b3e26872dsm2270835wms.8.2023.12.07.07.01.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Dec 2023 07:01:57 -0800 (PST) Message-ID: <369ec8d3-ef6a-4a4e-84e2-2c91b8293929@redhat.com> Date: Thu, 7 Dec 2023 16:01:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 04/10] mm: thp: Support allocation of anonymous multi-size THP To: Ryan Roberts , Andrew Morton , Matthew Wilcox , Yin Fengwei , Yu Zhao , Catalin Marinas , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain , Itaru Kitayama , "Kirill A. Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Alistair Popple Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231204102027.57185-1-ryan.roberts@arm.com> <20231204102027.57185-5-ryan.roberts@arm.com> <71040a8c-4ea1-4f21-8ac8-65f7c25c217e@redhat.com> <126c3b71-1acc-4851-9986-4228cb8a8660@arm.com> <94806b4f-2370-4999-9586-2c936955cb87@redhat.com> <3d49bcbf-1f9b-48e8-a91a-ede0762b795c@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: <3d49bcbf-1f9b-48e8-a91a-ede0762b795c@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-Rspamd-Queue-Id: DFB3F20105 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: qpybr76zwssegubnsngbidxg89b7eea8 X-HE-Tag: 1701961325-207944 X-HE-Meta: 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 JclGZWw/ 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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 07.12.23 15:45, Ryan Roberts wrote: > On 07/12/2023 13:28, David Hildenbrand wrote: >>>> >>>> Right, but you know from the first loop which order is applicable (and will be >>>> fed to the second loop) and could just pte_unmap(pte) + tryalloc. If that fails, >>>> remap and try with the next orders. >>> >>> You mean something like this? >>> >>>     pte = pte_offset_map(vmf->pmd, vmf->address & PMD_MASK); >>>     if (!pte) >>>         return ERR_PTR(-EAGAIN); >>> >>>     order = highest_order(orders); >>>     while (orders) { >>>         addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); >>>         if (!pte_range_none(pte + pte_index(addr), 1 << order)) { >>>             order = next_order(&orders, order); >>>             continue; >>>         } >>> >>>         pte_unmap(pte); >>> >>>         folio = vma_alloc_folio(gfp, order, vma, addr, true); >>>         if (folio) { >>>             clear_huge_page(&folio->page, vmf->address, 1 << order); >>>             return folio; >>>         } >>> >>>         pte = pte_offset_map(vmf->pmd, vmf->address & PMD_MASK); >>>         if (!pte) >>>             return ERR_PTR(-EAGAIN); >>> >>>         order = next_order(&orders, order); >>>     } >>> >>>     pte_unmap(pte); >>> >>> I don't really like that because if high order folio allocations fail, then you >>> are calling pte_range_none() again for the next lower order; once that check has >>> succeeded for an order it shouldn't be required for any lower orders. In this >>> case you also have lots of pte map/unmap. >> >> I see what you mean. >> >>> >>> The original version feels more efficient to me. >> Yes it is. Adding in some comments might help, like >> >> /* >>  * Find the largest order where the aligned range is completely prot_none(). Note >>  * that all remaining orders will be completely prot_none(). >>  */ >> ... >> >> /* Try allocating the largest of the remaining orders. */ > > OK added. > >> >>> >>>> >>>> That would make the code certainly easier to understand. That "orders" magic of >>>> constructing, filtering, walking is confusing :) >>>> >>>> >>>> I might find some time today to see if there is an easy way to cleanup all what >>>> I spelled out above. It really is a mess. But likely that cleanup could be >>>> deferred (but you're touching it, so ... :) ). >>> >>> I'm going to ignore the last 5 words. I heard the "that cleanup could be >>> deferred" part loud and clear though :) >> >> :) >> >> If we could stop passing orders into thp_vma_allowable_orders(), that would >> probably >> be the biggest win. It's just all a confusing mess. > > > > I tried an approach like you suggested in the other thread originally, but I > struggled to define exactly what "thp_vma_configured_orders()" should mean; > Ideally, I just want "all the THP orders that are currently enabled for this > VMA+flags". But some callers want to enforce_sysfs and others don't, so you > probably have to at least pass that flag. Then you have DAX which explicitly Yes, the flags would still be passed. It's kind of the "context". > ignores enforce_sysfs, but only in a page fault. And shmem, which ignores > enforce_sysfs, but only outside of a page fault. So it quickly becomes pretty > complex. It is basically thp_vma_allowable_orders() as currently defined. Yeah, but moving the "can we actually fit a THP in there" check out of the picture. > > If this could be a simple function then it could be inline and as you say, we > can do the masking in the caller and exit early for the order-0 case. But it is > very complex (at least if you want to retain the equivalent logic to what > thp_vma_allowable_orders() has) so I'm not sure how to do the order-0 early exit > without passing in the orders bitfield. And we are unlikely to exit early > because PMD-sized THP is likely enabled and because we didn't pass in a orders > bitfield, that wasn't filtered out. > > In short, I can't see a solution that's better than the one I have. But if you > have something in mind, if you can spell it out, then I'll have a go at tidying > it up and integrating it into the series. Otherwise I really would prefer to > leave it for a separate series. I'm playing with some cleanups, but they can all be built on top if they materialize. -- Cheers, David / dhildenb