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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id n36-20020a05600c3ba400b0040ed1d6ce7csm1745809wms.46.2024.01.31.06.20.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 31 Jan 2024 06:20:05 -0800 (PST) Message-ID: Date: Wed, 31 Jan 2024 15:20:03 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 0/9] mm/memory: optimize unmap/zap with PTE-mapped THP To: Michal Hocko , Ryan Roberts Cc: Yin Fengwei , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Catalin Marinas , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Michael Ellerman , Christophe Leroy , "Naveen N. Rao" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, "Huang, Ying" References: <20240129143221.263763-1-david@redhat.com> <4ef64fd1-f605-4ddf-82e6-74b5e2c43892@intel.com> <1fd26a83-8e6f-4b96-9d27-dd46de9488cc@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: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C2DBBC002C X-Stat-Signature: h7jksob9jb3tr6j1os8b4jxpdzdjtixy X-HE-Tag: 1706710809-911313 X-HE-Meta: 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 +z3hHRTi SSTHWjaXbY8kEj+j9cXT24iksAAXo+MyAlZGscAO+6Vi6uR9GVkuAlLWRiB5MOickfXS5/FvtPTzF/BV0baPaIpJcFPZAFt2IFB9sDdX2/wYxxF6AfSiVRFJhNbTG3ZGnvueqQ9BMUkiXgidfSqCBm2evoTzdA8ifcyszatoHWwg9Auuv1RICi0kCyQklIqu9e7gqMJ3cHk5wERgX+keJgoFs/Kb+F+c6V85hvlzHA69kgtIhoCRXKIkF6WlMflnrbhBcAQSYO+K4BRtMP1zoNwSjxSaU5ahIO3SStsnDWY9sorv8INuLy1W9OcG8nrSEFg7um0IeDC3r7nBv4nDDJSpPxJAZqhkHOpeI3NXZgySvf8hP8Et/BRzelghtj4qSzVVQyXyjBVyYggEzse0helraAQt00nD+kLsoH7AiVpUFld4ZhFiw2647lQ== 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 31.01.24 15:08, Michal Hocko wrote: > On Wed 31-01-24 10:26:13, Ryan Roberts wrote: >> IIRC there is an option to zero memory when it is freed back to the buddy? So >> that could be a place where time is proportional to size rather than >> proportional to folio count? But I think that option is intended for debug only? >> So perhaps not a problem in practice? > > init_on_free is considered a security/hardening feature more than a > debugging one. It will surely add an overhead and I guess this is > something people who use it know about. The batch size limit is a latency > reduction feature for !PREEMPT kernels but by no means it should be > considered low latency guarantee feature. A lot of has changed since > the limit was introduced and the current latency numbers will surely be > different than back then. As long as soft lockups do not trigger again > this should be acceptable IMHO. It could now be zeroing out ~512 MiB. That shouldn't take double-digit seconds unless we are running in a very problematic environment (over-committed VM). But then, we might have different problems already. I'll do some sanity checks with an extremely large processes (as much as I can fit on my machines), with a !CONFIG_PREEMPT kernel and init_on_free, to see if anything pops up. Thanks Michal! -- Cheers, David / dhildenb