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 66F20106ACEA for ; Thu, 12 Mar 2026 21:19:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9B1776B00BB; Thu, 12 Mar 2026 17:19:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9682E6B00BE; Thu, 12 Mar 2026 17:19:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 86A7E6B00C0; Thu, 12 Mar 2026 17:19:49 -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 7404A6B00BB for ; Thu, 12 Mar 2026 17:19:49 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 1A71BB955C for ; Thu, 12 Mar 2026 21:19:49 +0000 (UTC) X-FDA: 84538678098.03.6A79BF5 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf17.hostedemail.com (Postfix) with ESMTP id 81A884000F for ; Thu, 12 Mar 2026 21:19:47 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=oAmgV2ar; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.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=1773350387; 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=UJW95MAAwk02Yo5Bqs/qbwpbpbptX/VVoXNWJEuoRrQ=; b=IMrTmx1dTyJNHbJ2VcIQVEkLyhvGWKEK6zPVXm5Oy2X3uHxGkVWvw9AvrvcA57YV3K81r9 BWgL6TYaon8tS86l8sRCCChvrwBhwihL6/pDXlDZ/a8GPpcXPEJhxxs24MDAlDKzWH2V4Q S+T0Ro1a+wl4+m0bopSW1NXF1BAxBxE= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=oAmgV2ar; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.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=1773350387; a=rsa-sha256; cv=none; b=aty9ZMxHJDYDPdCjgtzcUIiLIxsVPRyKHhW4CzYgow9MpHBlbbls3l8oLBDaUh/6tKokBH HfOVNaRyvSHpD2f0xNtuvKcFwiS64JULOwq9D72eEpKsmJJ97rm12Pw8wrenh0v8OkYqyJ xw/OMdYzqqTTtdMgcOWLahZAvpscCos= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id A8CA860142; Thu, 12 Mar 2026 21:19:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CE64C4CEF7; Thu, 12 Mar 2026 21:19:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773350386; bh=b/n1AB5/3Poo0rQsSnXTnJrEIrDJtXE5V+mRQh+spI4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oAmgV2arw8JwtUgPzmUkQXEI7qwOzfCbG1n6XzBr808nXkT+OTjcRoZGUbQVs225r 9oL/+sG4BcrmV3hycYoRG47G00JbqB8hTMHM0ptNJU7mjsuefL4tvMRzuId6W14LfC IhC3XdsJFW4ICAXdSYDHW57MGspUq0ZIKv9UDCO2lWLUNOBuhtz5raqUE/EXj07yKw lSTutMzLLYbUh0c0Tgi5w3ADbIccOK0ATm2IM7ZQRhFJKmmxtB8JJh2aueu/1QEbET doHY7gQJmOOlG2DNwXemCr96moZ7CqMMX0kfhuAXOVJR/pnLfkaz6t22RHEZ5xmisP wmCkSME14rwIQ== Message-ID: Date: Thu, 12 Mar 2026 22:19:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v15 11/13] mm/khugepaged: avoid unnecessary mTHP collapse attempts 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.Howlett@oracle.com, lorenzo.stoakes@oracle.com, 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: <20260226031741.230674-1-npache@redhat.com> <20260226032631.234234-1-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: <20260226032631.234234-1-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 81A884000F X-Stat-Signature: 4ubcbtwgo8e5p7q881ekkka4yi9cao3n X-Rspam-User: X-HE-Tag: 1773350387-905631 X-HE-Meta: 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 ruJcqxUo WtF/T5pqTKGjO3rAes2LUYN9Kg5HOI5B+ve7y Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/26/26 04:26, Nico Pache wrote: > There are cases where, if an attempted collapse fails, all subsequent > orders are guaranteed to also fail. Avoid these collapse attempts by > bailing out early. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 35 ++++++++++++++++++++++++++++++++++- > 1 file changed, 34 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 1c3711ed4513..388d3f2537e2 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1492,9 +1492,42 @@ static int mthp_collapse(struct mm_struct *mm, unsigned long address, > ret = collapse_huge_page(mm, collapse_address, referenced, > unmapped, cc, mmap_locked, > order); > - if (ret == SCAN_SUCCEED) { > + > + switch (ret) { > + /* Cases were we continue to next collapse candidate */ > + case SCAN_SUCCEED: > collapsed += nr_pte_entries; > + fallthrough; > + case SCAN_PTE_MAPPED_HUGEPAGE: > continue; > + /* Cases were lower orders might still succeed */ > + case SCAN_LACK_REFERENCED_PAGE: > + case SCAN_EXCEED_NONE_PTE: > + case SCAN_EXCEED_SWAP_PTE: > + case SCAN_EXCEED_SHARED_PTE: > + case SCAN_PAGE_LOCK: > + case SCAN_PAGE_COUNT: > + case SCAN_PAGE_LRU: > + case SCAN_PAGE_NULL: > + case SCAN_DEL_PAGE_LRU: > + case SCAN_PTE_NON_PRESENT: > + case SCAN_PTE_UFFD_WP: > + case SCAN_ALLOC_HUGE_PAGE_FAIL: > + goto next_order; > + /* Cases were no further collapse is possible */ > + case SCAN_CGROUP_CHARGE_FAIL: > + case SCAN_COPY_MC: > + case SCAN_ADDRESS_RANGE: > + case SCAN_NO_PTE_TABLE: > + case SCAN_ANY_PROCESS: > + case SCAN_VMA_NULL: > + case SCAN_VMA_CHECK: > + case SCAN_SCAN_ABORT: > + case SCAN_PAGE_ANON: > + case SCAN_PMD_MAPPED: > + case SCAN_FAIL: > + default: > + return collapsed; > } > } > LGTM, but I do wonder, given that you have the "default" case, why spell out the ones that fall into the "default" category? I'd strip those /* For all other cases no futher collapse is possible */ default: return collapsed; Acked-by: David Hildenbrand (Arm) -- Cheers, David