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 0E486E9A050 for ; Thu, 19 Feb 2026 17:09:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6F00A6B008A; Thu, 19 Feb 2026 12:09:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6B11B6B008C; Thu, 19 Feb 2026 12:09:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 57BE86B0092; Thu, 19 Feb 2026 12:09:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 428BC6B008A for ; Thu, 19 Feb 2026 12:09:17 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 10F711C4C1 for ; Thu, 19 Feb 2026 17:09:17 +0000 (UTC) X-FDA: 84461841954.09.DA74511 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf13.hostedemail.com (Postfix) with ESMTP id 54F2A20019 for ; Thu, 19 Feb 2026 17:09:15 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=cDz1BuWN; spf=pass (imf13.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-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1771520955; 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=jI3if3NIQc22/QmQNEOIA3RNLD+gKfFnXOQ8mFyFj7A=; b=gIx4tHYJOD0e3hVXdJ4Lb20VjA899gqFW/3ipmxYnJswGfeFbdqhl7EmogMVYuM1OvpujB AdvhNhrxFerKAO1xiycCOxs3c8KDCbc2vMt9ZfmV7+py3CZZz93dIHj87X4BMAY0s2h4CK niKdEUDpbC8YX4+PJ00cLBKJZrIWK7E= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=cDz1BuWN; spf=pass (imf13.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=1771520955; a=rsa-sha256; cv=none; b=E5akhQ9USsmuYXbS4a8suNtk5ZFw7nzFS2G4YCA1V4vE9XkQLBGwZ73kx2FzC+X4NiWZIF Y010zoPlIiHe5sUsHyiR3OzF5eyBM5eWyR/RnmeUdkwN0A7jwxbcd8AxN3qVOxfMKU7/lW Z77mUZ1fp0F8ufOHdAwpTEXVaySQdUk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 93B4D6132F; Thu, 19 Feb 2026 17:09:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C43D8C4CEF7; Thu, 19 Feb 2026 17:09:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771520954; bh=UjbEwHCLAlRPRnGztN5Qtc5zs+16ZgPdDu1lHfw3ues=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=cDz1BuWNxxN7WcY42EaYiFgRbNk1Bz9YL8BF23ErfOnmrLOgLQ9ip/OoOlDShXdp6 iWx1WNJggasZvbnikY+s8C8YLPEZKSPOvuDXzqKG8OiJ+oeINw9+9Cn143357ZIDmY QZuWb+enqgFxxcVMvHEp/12lEGD1F0gxds6EbR80AQ2glSePSOybbPNxpxfFCaaXMR 3Y7iCDpaT5hNwtZJUU4pB+dLmsx2RBbf43yPhmS73Q9Vzm6R+fNl+xXuC1Wj9o0zn8 2zs3SwfbFETH1rdcEI3KVb8wKZ03fEMoffRNxURGuroO/oz/9z3tWRJGGhagotM2ME gGR/Y5iPVyGaw== Message-ID: <43a065a3-dcff-4d6a-8c5a-c68cda7065ee@kernel.org> Date: Thu, 19 Feb 2026 18:09:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] Beyond 2MB: Why Terabyte-Scale Machines Need 1GB Transparent Huge Pages To: Zi Yan , Johannes Weiner Cc: Usama Arif , willy@infradead.org, Lorenzo Stoakes , Andrew Morton , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, riel@surriel.com, Shakeel Butt , Kiryl Shutsemau , Barry Song , Dev Jain , Baolin Wang , Nico Pache , "Liam R . Howlett" , Ryan Roberts , Vlastimil Babka , Lance Yang , Frank van der Linden References: <540c5c13-9cfb-44ea-b18f-8e4abff30a01@linux.dev> <3485c8c8-9bfc-4725-885a-626e79d0aebb@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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: 9fz86f3j1mr11kf8dypxf6gbdcxwekgo X-Rspam-User: X-Rspamd-Queue-Id: 54F2A20019 X-Rspamd-Server: rspam01 X-HE-Tag: 1771520955-954287 X-HE-Meta: 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 fnApl1GL O6WiZGqBXPRmMGRMlvlE5dPXsSXaUtvWTlLuuG2rU37wTYrKUdsNY3vRDmLX0F5eVK6GblFubI9YCyLfsPwTBu9q5g8iP8PTpSXchUs1Ll7TNS0l1SWvb/w+kKMBQo0m412az2by8kvjHDmzdO++rX0pzjqKI+Nct83vfqxWHAdiRPiXwns7CRtjKu6sWCA6xcFUMSDuZG+JnjjQtzySsYH15RJ78QqYSBEzgItLWjaGzQMaDd8NlevrZZY/1LsKojXnYpSR02FN+PP6xSBk9wkUNmXjeduLQkMWB 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 2/19/26 17:52, Zi Yan wrote: > On 19 Feb 2026, at 11:48, Johannes Weiner wrote: > >> On Thu, Feb 19, 2026 at 05:00:19PM +0100, David Hildenbrand (Arm) wrote: >>> >>> >>> There once was this proposal where we would, instead of splitting a THP, >>> migrate all memory away instead. That means, instead of splitting the 1 >>> GiB THP, you would instead return it to the page allocator where >>> somebody else could use it. >> >> With TLB coalescing, there is benefit in preserving contiguity. If you >> lop off the last 4k of a 2M-backed range, a split still gives you 511 >> contiguously mapped pfns that can be coalesced. > > Which CPU are you referring to? AMD’s PTE coalescing works up to 32KB > and ARM’s contig PTE supports larger sizes. BTW, do we have PMD level > ARM contiguous bit support? Yes. It's used for hugetlb only so far, obviously (np THP > PMD). -- Cheers, David