From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1E06AE9B258 for ; Tue, 24 Feb 2026 13:21:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 18A386B0088; Tue, 24 Feb 2026 08:21:38 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 10E416B0089; Tue, 24 Feb 2026 08:21:38 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F317D6B008A; Tue, 24 Feb 2026 08:21:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id DC50A6B0088 for ; Tue, 24 Feb 2026 08:21:37 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 7E9D81B484C for ; Tue, 24 Feb 2026 13:21:37 +0000 (UTC) X-FDA: 84479412234.03.437E232 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf12.hostedemail.com (Postfix) with ESMTP id BF76D4000D for ; Tue, 24 Feb 2026 13:21:35 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=bctsJnyy; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1771939295; a=rsa-sha256; cv=none; b=UGOyURJkw2b8pfuj8/5qC8oXd8wyyKrYbfLCwO8v26mEK9I65XpEvxY2spT6pzu6ubpRzZ e14QMyMhiEB1+a0wXw3OpDYwC1l3HqHBXKSagiAadGmIPXTuMtsWZV562JR5+dtiQS5OGW h1sboSl6w8Xja2Os3nx3359HCMz/MPo= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=bctsJnyy; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1771939295; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8xYym5AGEAwFxZSBKb+Ypj+3/D0iUuZi+apmqwCQTJs=; b=X0yyfAXTt/VS1KwgeUrshlQyV4rdW+jhMOMBq87llrGbGI0TcKTNAb8RLHvKqEbUWjb0NR 5SIvssHk9Zkve+REFeGHIXYaBjEd6veO6pcbrhvg3G4U75Y5DurIR3GotI+mbs+3ofCtDG FtmvhZjRxDgnKKn1T4WWlawuP1zMiUc= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id D8FB061335; Tue, 24 Feb 2026 13:21:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3CFBC116D0; Tue, 24 Feb 2026 13:21:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771939294; bh=X5lX3knKyo5M4XUmowZbt7UXczBV7awEnAyq21gL2Sc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bctsJnyyVx0cPlaGpbetUsIn8lovH8Zuaa4PovF6gxCzht/LMZmfR3rORBrj9DcZu GDRR+bVTFabEnynPE6Xp7Vewg52oQz4Yj1zcMwi7zdewVCv/RdlSMf8Osk4wgqurf2 xrN9WAyiRjwSUbGMYU/KrBUUIMKFdzV2dmDZOq0BZNLY0DFeOB4HuLIv03cSFMfG9D UbqyCFr3UtORFaNtD/lZB3820tehoVQGRD1MOSGPpy0V6Ho5ZcSe/AKC8NXhItUynq 8DYoYGuCuiOfqufxNVDJXrR/2P4mxi/BN/Epzcyas7oTUBcV/voQTrzNl8Ed6XdtPH ZC2HK4MWtnYhg== Message-ID: <2553a75a-6dc8-4295-96b3-58367879751c@kernel.org> Date: Tue, 24 Feb 2026 14:21:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fork: zero vmap stack using clear_pages() instead of memset() To: Linus Walleij , Kees Cook , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-mm@kvack.org, Mateusz Guzik , Pasha Tatashin References: <20260224-mm-fork-clear-pages-v1-1-184c65a72d49@kernel.org> 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: <20260224-mm-fork-clear-pages-v1-1-184c65a72d49@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: oaji8i8fgg8qayubf8dmazxumsmpacy7 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BF76D4000D X-HE-Tag: 1771939295-908369 X-HE-Meta: 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 dPXOL4u7 XstJR6LaEBecM26zaYdmkphJ2wrl9qdEy2OZF3ZHOfO5w8kl6OzBjVcjo2k8QqtoAdDB3xd0OEMUr/ItkI9TjVS4kSmg1nsO7Ne//bgwF/OAkAZTnNkM2R503g69MFt5KYVG+nEm2SP7F2c/5iFMLh1VundEH28ct4WHsoFdPlJNX6FlDzz601bhttrmZEBCW2yNKPmNg+p2ITcON0Rv02ou+mEVBa54F1bz93XoGkODntdbm8uaGJBJnf+0qJB3orI+yr0sDsuVX5fLJtUEdO7HgVWrgpiREGa5g98LH3YTJymDyJAmxq5UPa6Aee7hZTgx9YNzaGrdyX6nEDLH1wpaq/UEQx3qMdiFNLBup3N+37p5ywzna8B2JNKCFQxLnHA1niyO4I7knDYTAkmQZyOpMnOuqaWKBsVr96cgXc+y6wG4HGFjFxy3OLcKThTfluxq0 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 2/24/26 11:26, Linus Walleij wrote: > After the introduction of clear_pages() we exploit the > fact that the process vm_area is allocated in contiguous > pages to just clear them all in one swift operation. The pages are virtually contiguous (vmalloc IIUC), not necessarily physically contiguous. For clear_pages() that should work. > > Suggested-by: Mateusz Guzik > Link: https://lore.kernel.org/linux-mm/dpnwsp7dl4535rd7qmszanw6u5an2p74uxfex4dh53frpb7pu3@2bnjjavjrepe/ > Suggested-by: Pasha Tatashin > Link: https://lore.kernel.org/20240311164638.2015063-7-pasha.tatashin@soleen.com > Signed-off-by: Linus Walleij > --- > kernel/fork.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index e832da9d15a4..88d78ccef245 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -345,7 +345,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) > stack = kasan_reset_tag(vm_area->addr); > > /* Clear stale pointers from reused stack. */ > - memset(stack, 0, THREAD_SIZE); > + clear_pages(vm_area->addr, vm_area->nr_pages); LGTM. Do we have any idea about performance impact etc? -- Cheers, David