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 632F9CD8C85 for ; Tue, 9 Jun 2026 08:12:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C74C86B008A; Tue, 9 Jun 2026 04:12:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C24CA6B0093; Tue, 9 Jun 2026 04:12:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B13EF6B0095; Tue, 9 Jun 2026 04:12:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 9FBDC6B008A for ; Tue, 9 Jun 2026 04:12:18 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 3C9FA1C26E1 for ; Tue, 9 Jun 2026 08:12:18 +0000 (UTC) X-FDA: 84859656756.24.20E2118 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf14.hostedemail.com (Postfix) with ESMTP id 5EFB210000C for ; Tue, 9 Jun 2026 08:12:16 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mBNfFi7p; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780992736; b=k5EtgqZytUTsURb4J6SgxS3y/ssKs3xNOwqXscSvKYegHzTw0aNoi7HsTwkucmDp+981+s 1bk2eK/OGiLVnRg6JDH0GmpqnUl9QqpIhDmY6jALqQVlUlDJWhXagX+u8eJXnofntHBz// ANvX7XASxXNIqufSJnlYHbCthfzO35s= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mBNfFi7p; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780992736; 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=6iy6WqC0AyHBkc7kR6hVPweXwlBpVwgmOI4XY3Av07c=; b=bVWjOswyHD9nSqs5Su82HxARafUFFRw/lLsj2IvP1C0fnKLHkTSSSNgFiqlCghrcJ6d8gQ 43ckXDuRahW3BI8NuTkF0ODh5F4jYaVLWR9dcF0Uhy6YqrLHvuOWt8j8+2xedaRxnrxOVP M8Sny75zExPB+vINtnKmuv0tN/BpHEo= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 5994F42A96; Tue, 9 Jun 2026 08:12:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 414941F00893; Tue, 9 Jun 2026 08:12:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780992735; bh=6iy6WqC0AyHBkc7kR6hVPweXwlBpVwgmOI4XY3Av07c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mBNfFi7ppl4+IUjL4paapjKUUGOFLBiQiAJsdBQDha5aP4aWh/vLeYKkEYguX4EB8 ZBU3SBR96jhLjV1NqLg4LNvs+iSd0iB/5Y2Dd3MlHOIpLsMuIOehzo5Sn5rY7D12en A1bhQYr+0gvzV+z6xEZjwdZMka0w5T8ppl9kn1Rnoq2Dl/XprTERRJTJ+SImEIrg6Q CRLqd/6h4NBJOvnwoCC87TC0tOF6mamlktlGki3+Pt4XlKIrui0MLA+tnn4vUkhYQ7 XFbwRGDgXNzeKKthtrWKBPW4b+luJ0ChgndRKis1p9FUreefx9dSGBhJFmU/wEXuSG eAUkN7WiysX/A== Message-ID: Date: Tue, 9 Jun 2026 10:12:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: New design To: Matthew Wilcox , "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli 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 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5EFB210000C X-Stat-Signature: 9kkxjgzi8upynspdzfwu4ppgch9ah6hh X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1780992736-102171 X-HE-Meta: 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 jkQOJRwO xu+QauFtMADN1x+c0Zyc8GhZsAPiL037Lpn4ZN0TCOrlfckmpgiZtQvH2LNmCzU12MIA92gEJqRTDN6uNOx9wo4SBzQWwWhNp903Eb06ELcXBI7bSa4ZAYD/nTmoN20j9Bnm2kNxcANorDzy1gTkiDu5tt/mt8IcXF9IedVnRaQpY+GBBD8i+1rVQQYRtC8UuNiUPgDlCyktyLLMA2bLYzxYbzsTVDWCMC+LVcpQWhzt1XKX/JUer2lmF28+V1SRKk+59+QXscKhQPUxp7rxY+VZAWungJxqSPR+YHzxev9uASXB7vjMZGu0Lo+tDrGfjLH5SaTXsNjAPI/Exl0bIVf8mXWoZ5elx+VKIvuu/X36GhL1mzugQZWJpMrBAb9Ds5XAH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/9/26 05:58, Matthew Wilcox wrote: > OK, here's how I'd structure this: > > 1. Introduce PG_zeroed for buddy pages > 2. Set it if init_on_free is set > 3. Set it from balloon driver > > https://lore.kernel.org/lkml/c7094de807c0e963526686e1d245bc76193b1a92.1776689093.git.mst@redhat.com/ > > but add FPI_ZEROED instead of an extra bool parameter. > > 4. Introduce page_is_zeroed like this: > > static inline bool page_is_zeroed(const struct page *page) > { > /* > * lru.next has bit 2 set if the page is already zeroed. > * Callers may simply overwrite it once they no longer > * need to preserve that information. > */ > return (unsigned long)page->lru.next & BIT(2); > } > > (you'll notice this is similar to page_is_pfmemalloc() but it doesn't > need to be in mm.h) > > This step is going to be a bit fiddly. We weren't expecting to return > multiple flags in page->lru.next, so clear_page_pfmemalloc() just sets > page->lru.next to NULL. So somewhere we need to make sure that > page->lru.next is definitely NULL, and then allow both the zeroed and > pfmemalloc flags to be set in it. > > The important part of this is that it allows the zeroed flag to be > returned from the page allocator without introducing pghint_t like you > did in v2. I previously raised (in v2? not sure) that we could using a pageflag that are only used for folios, and then simply clear that flag on the folio allocation path such that we don't get false-postives with the bit set. > > 5. Now you can start skipping various zeroing steps higher in the call > chain. > > I understand David's disgust with vma_alloc_zeroed_movable_folio() > but that is surely a separate cleanup and nothing to do with this > patchset. Well, in my reality, we're just finding interesting ways to work around the fact that GFP_ZERO sometimes does what we want, sometimes doesn't. So we leak information out of the buddy to really only handle one scenario: fixing up GFP_ZERO currently sometimes not doing what we want. I'm afraid we couldn't use the above trick to punch zeroed pages back into the buddy: some random user doing alloc+use+free would be unaware that there is a bit to clear. So I assume really only folio allocation would make use of this, to work around our problematic GFP_ZERO implementation. -- Cheers, David