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 75797CD6E7C for ; Fri, 5 Jun 2026 18:07:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8BC1F6B0005; Fri, 5 Jun 2026 14:07:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 893E36B0088; Fri, 5 Jun 2026 14:07:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7A93E6B008C; Fri, 5 Jun 2026 14:07:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 687786B0005 for ; Fri, 5 Jun 2026 14:07:21 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 247664023B for ; Fri, 5 Jun 2026 18:07:21 +0000 (UTC) X-FDA: 84846641082.20.69D652E Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf11.hostedemail.com (Postfix) with ESMTP id 3ABCD4000A for ; Fri, 5 Jun 2026 18:07:19 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=alsX+KfK; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf11.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1780682839; 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=/Nhf4jMO4wZRRzTPNpV/mvbXK0GYYQL5VEX2HgG0GMc=; b=OOx+QQ6MRosbgJqEeXBE0eKNv2bHAWO2VBShsBiPBzEnlQ/g7qE3HPA/yDiDkcVfymEC4R Nn/dy9uCvgZ48thtVPjObu9WXEy3D1rdhL8QIVmS7paTsf4QIK6Gyb0Q5lHlj8AL9Nyg75 3Ux/BQ7N1z6SrMR/s+juCZR+uQENqCQ= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=alsX+KfK; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf11.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780682839; b=U5D9K4NvnI0xwUv8J8kMecAQlPtRnBmO0J90cBxlTYuEtMVobW2RNvDwwMq36DbMuKCO4l z6zKsHgVTPKVHWBtbViuzuKfVS1eiHZnVEDxd6a7YKawi9booZcqgo8FUj7zJz5dkywbOX GXAmlDHpKkzOLA1mXMXsBomY6OUEqAc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 3800D4348E; Fri, 5 Jun 2026 18:07:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A07371F00893; Fri, 5 Jun 2026 18:07:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780682838; bh=/Nhf4jMO4wZRRzTPNpV/mvbXK0GYYQL5VEX2HgG0GMc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=alsX+KfKpBh3DHmOFR5AfpAGL8a8etxlfDAQgLlShE1jlMui4LaKD9+wiWQ42voDK 1xswb8uIL6om3S/gp1xwoeb6UEV8V6IWwkyfi/D9E9zDXUSCioSbKg2AHA+ZrY0BFE 2KZS4fs3fhWH8FIlfVJojSt6RX0bDEHEVF7OVAvL9h5+zR4sBRDLw10YjMYHjRWVgn LXwdC3Lvd34Oo6pG+yR6gf6mEfv/QDjo+K/VcfEBfifFGZZYnQsb2tocaaxiIlJQfy HTJTIbHVLR3z0JuQ/r1Hfi/yguSuZcybRH5O8fSD4DHd+AMDmED9H+IOjsNtAauyay 1dFEy9B6/ISyw== Message-ID: <177704e1-03b3-4791-9a69-9b83b72d61d5@kernel.org> Date: Fri, 5 Jun 2026 20:07:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v19 00/14] khugepaged: add mTHP collapse support To: Nico Pache , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260605161422.213817-1-npache@redhat.com> 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: <20260605161422.213817-1-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3ABCD4000A X-Stat-Signature: hktf8som5zge7hbn1gzoaf9jqz8p6j6m X-HE-Tag: 1780682839-353588 X-HE-Meta: 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 U8vaOLpu 2dHL27NtX4Ms1ozoQASE6sDUOO/FzZKU2+Ty5fIvX+NpdlnhfmC5PmWLGhpNJ5j3Y8IvGEcgTbox1B0L7ZqbsPzwxtsP3JI39hL6lp3neEUXm9wV47vYqaY9ZkbDcNSn9qDcEAR/Xsz9PdCojnbpx3sUS7DAA3kNNCm9eRUKU/y0Flz7EPqphE6sB7XiTkPNV+7pCMiqGHEMhjBeNqcxFsakvbEyzjdO2+56QGhM51Qpq323egPb64rIgeUiayUdSMSF/5Qi7O4E6ZzFTCskJgxKSTCn85+rc7jK9VSjqKGceFzcjGn1sA/RyHoGxsUQPdZ4PyUjklMoqCRs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/5/26 18:14, Nico Pache wrote: > The following series provides khugepaged with the capability to collapse > anonymous memory regions to mTHPs. > > To achieve this we generalize the khugepaged functions to no longer depend > on PMD_ORDER. Then during the PMD scan, we use a bitmap to track individual > pages that are occupied (!none/zero). After the PMD scan is done, we use > the bitmap to find the optimal mTHP sizes for the PMD range. The > restriction on max_ptes_none is removed during the scan, to make sure we > account for the whole PMD range in the bitmap. When no mTHP size is > enabled, the legacy behavior of khugepaged is maintained. > > We currently only support max_ptes_none values of 0 or HPAGE_PMD_NR - 1 > (ie 511). If any other value is specified, the kernel will emit a warning > and mTHP collapse will default to max_ptes_none=0. If a mTHP collapse is > attempted, but contains swapped out, or shared pages, we don't perform > the collapse. > It is now also possible to collapse to mTHPs without requiring the PMD THP > size to be enabled. These limitations are to prevent collapse "creep" > behavior. This prevents constantly promoting mTHPs to the next available > size, which would occur because a collapse introduces more non-zero pages > that would satisfy the promotion condition on subsequent scans. > > Patch 1-2: Generalize hugepage_vma_revalidate and alloc_charge_folio > for arbitrary orders. > Patch 3: Rework max_ptes_* handling into helper functions > Patch 4: Generalize __collapse_huge_page_* for mTHP support > Patch 5: Require collapse_huge_page to enter/exit with the lock dropped > Patch 6: Generalize collapse_huge_page for mTHP collapse > Patch 7: Skip collapsing mTHP to smaller orders > Patch 8-9: Add per-order mTHP statistics and tracepoints > Patch 10: Introduce collapse_possible_orders helper functions > Patch 11-13: Introduce bitmap and mTHP collapse support, fully enabled > Patch 14: Documentation > Went through it and didn't find any blockers. Let's wait for Lorenzo's assessment. If he also doesn't find anything major, I think we can move forward with merging it and handle smaller things as follow-ups. -- Cheers, David