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imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=W62OQ1ai; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1771003609; a=rsa-sha256; cv=none; b=rPys2q47J00jNL1KMTBeh32GjTjh0JokbdLu8kcG1O5bLfdOEzWLviy2aDFNv4ziPJk8F+ +D7RIW0/mNUtMqMaaTMj6ad/G++LRYJABLfhTsFviwkCk081SxatSRjNkol6JPcF3RnVD7 wNrg51Eo/pjsHOXut7cUMcsM84crAr4= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 78A0860054; Fri, 13 Feb 2026 17:26:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BF58C116C6; Fri, 13 Feb 2026 17:26:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771003608; bh=l1r8VLb/JxuCT8M2BTEbNThkHetvDmAF8/je/HgRiAg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=W62OQ1aiCmeKbDa2usSHRJV+w71QVJ84yJcAl7azk5OfW2VgB1aqQgh6u6nRPL3Km P21Sv7sVvIE//qb64Qx0F+7Lm60IMNHf/Wz8lUVFo8nuDgeAmpjXocLv9u5JPxojHu LfwzNKlZw7NVo3quoFz/2i3m55dPOVJ3Kg3sqTrey8UAt9TyacHjMFpAKUpmuzaP5S IMN9Ngapfkef35TWY9cw1772DBbcDi4/hM4kibm5jaV178nw+TwmAGDO+4Z04/PgNW IRIkir7WKM/0FxD5fV5QUPj2cqmO2AXf+1PJhFFnYrYg9yKuM31mhEp872/CH2+aWT NK9KR5kfDzPpg== Message-ID: <764792ea-6029-41d8-b079-5297ca62505a@kernel.org> Date: Fri, 13 Feb 2026 18:26:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] mm/mprotect: 2x+ slowdown for >=400KiB regions since PTE batching (cac1db8c3aad) To: Suren Baghdasaryan , Pedro Falcato Cc: Luke Yang , dev.jain@arm.com, jhladky@redhat.com, akpm@linux-foundation.org, Liam.Howlett@oracle.com, willy@infradead.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 57A8480011 X-Stat-Signature: i9i1hnoqqdgp9i5jo8yzshj88bnhj663 X-Rspam-User: X-HE-Tag: 1771003609-311182 X-HE-Meta: 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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 2/13/26 18:16, Suren Baghdasaryan wrote: > On Fri, Feb 13, 2026 at 4:24 PM Pedro Falcato wrote: >> >> On Fri, Feb 13, 2026 at 04:47:29PM +0100, David Hildenbrand (Arm) wrote: >>> >>> Hi! >>> >>> >>> Micro-benchmark results are nice. But what is the real word impact? IOW, why >>> should we care? >> >> Well, mprotect is widely used in thread spawning, code JITting, >> and even process startup. And we don't want to pay for a feature we can't >> even use (on x86). > > I agree. When I straced Android's zygote a while ago, mprotect() came > up #30 in the list of most frequently used syscalls and one of the > most used mm-related syscalls due to its use during process creation. > However, I don't know how often it's used on VMAs of size >=400KiB. See my point? :) If this is apparently so widespread then finding a real reproducer is likely not a problem. Otherwise it's just speculation. It would also be interesting to know whether the reproducer ran with any sort of mTHP enabled or not. > >> >> In any case, I think I see the problem. Namely, that we now need to call >> vm_normal_folio() for every single PTE (this seems similar to the mremap >> problem caught in 0b5be138ce00f421bd7cc5a226061bd62c4ab850). I'll try to >> draft up a patch over the weekend if I can. I think we excessively discussed that during review and fixups of the commit in question. You might want to dig through that because I could have sworn we might already have discussed how to optimize this. When going from none -> writable we always did a vm_normal_folio() with anonymous folios. For the other direction not. -- Cheers, David