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]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0B92C4345F for ; Thu, 25 Apr 2024 08:57:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 78E0A6B0092; Thu, 25 Apr 2024 04:57:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 73D636B0093; Thu, 25 Apr 2024 04:57:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5B60B6B0098; Thu, 25 Apr 2024 04:57:12 -0400 (EDT) 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 395826B0092 for ; Thu, 25 Apr 2024 04:57:12 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id DBE931A03D9 for ; Thu, 25 Apr 2024 08:57:11 +0000 (UTC) X-FDA: 82047449862.19.B61CD3A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf05.hostedemail.com (Postfix) with ESMTP id 73D5210000F for ; Thu, 25 Apr 2024 08:57:09 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MBSPA2yH; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1714035429; 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=z4Acf1+QJQLYid45sCXlTITj3Su+r1/KdkNqXgWo+Hw=; b=gZWo+K3GCQsavWBduFKRABp3cCCl0KlK3culR7cDWIk5sEaGazNadfrM81X4UKzd/6MbYz BtRxRhEVBQj10++I8d2RUcVlfTj0R1Ugr+Rm0MzEGBSOEu/nvtOvHA1gsVIlYBZOKUctWA WyoXeQdcaMzpdbMaKi7lvtlP0N2VApU= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MBSPA2yH; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1714035429; a=rsa-sha256; cv=none; b=69MzTFu/HZ02Ul90OtSf2oRxIqfAQgELTVtt11kFvNSvQtxvmtcDDJmllcnbUjPIibhNnW wnrDa8ZxXqqDvwlE3RVSDj2Jx88zvaip4p7+NJ8l49b1QCLmTFbObWAL25kmLegEf14rYZ zauRgpuhur7Sdc/kkiGwK0YXQE9lwXI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714035428; h=from:from: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:autocrypt:autocrypt; bh=z4Acf1+QJQLYid45sCXlTITj3Su+r1/KdkNqXgWo+Hw=; b=MBSPA2yH7mwEFirmSeBF3BqoFRG3Ix32jUPt2T7Go34AeEIhX6UgrBCx1wOUuhcFrq4um/ RwqHv5RAM/WSGegk1biMKnIg3Np4VVDRBFWUydpyIu1Gw2bJr91DvgTdH15okhl0nnoB0J NXnMUCIbbAKPXvg0bcIhF3lpjRQTCnY= Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-76-N6VFfzf1P-CdXPSew8PHDA-1; Thu, 25 Apr 2024 04:57:07 -0400 X-MC-Unique: N6VFfzf1P-CdXPSew8PHDA-1 Received: by mail-lj1-f199.google.com with SMTP id 38308e7fff4ca-2d87d146022so5703981fa.3 for ; Thu, 25 Apr 2024 01:57:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1714035425; x=1714640225; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=z4Acf1+QJQLYid45sCXlTITj3Su+r1/KdkNqXgWo+Hw=; b=K7dNjcGr0wzxeUlqMEhyznJWD1jH46+sCT9d2FBtc/CjLrRWqAU1FVpji1Mu+KiD/b Zca0Hfz2HaQPOlF2c2tu5/Xj4NGXEKx9uNHKyvSUwU5MSkzX1bFPub22uuasDCRicvZj OeQ46AaY9izfcLLb5vbqKizCRM5mvCuqXWsNS6mLg5svA9z682r8p+l126FP49GxnwbH rhMIqcjJ6homj73kNj/6OLKeSBapjiitcCcggZxRp+lUTtsB3hVAJyWNZegWTOXpJxZV wltjvO9MvXxg1NXW+uFcP0MXO967UkBQjOQFWhDq6O8I0aUywLi/Ml/oPK+7Kg8cIURw Jd/A== X-Forwarded-Encrypted: i=1; AJvYcCX/mp65gsROQgzc73YSl7XJSDSLQOwMUiWk0kNJSOspuBrIKUXNZNp2E3FbOgfG9SpofOAjWNk/tVt/h5HWgcwf0/Q= X-Gm-Message-State: AOJu0YxAk4Fv6SP4KqyhARz4gBSnL2i8HuRMvsXvGyA+j2t5wMW/al9c 69969MxLJbxh85gqRFtsVWwmZ6Zc6003T0bVVfCnvkDNCgyBXgjZ5BGGWCqUUBNwhIG7dkasBpG tn99F8sqO9bjxP78ioaNQr+a+pHFjYv4j1tyoGwplBqsf4CGr X-Received: by 2002:a2e:848f:0:b0:2de:9e31:5011 with SMTP id b15-20020a2e848f000000b002de9e315011mr2537217ljh.24.1714035425475; Thu, 25 Apr 2024 01:57:05 -0700 (PDT) X-Google-Smtp-Source: AGHT+IF+0qMo5BWRinGlbLJjrts+NIrJBiHVAT3aROb6lBsPp9cMxfaGKSNmkMW+MkyNC+jdAHyaWw== X-Received: by 2002:a2e:848f:0:b0:2de:9e31:5011 with SMTP id b15-20020a2e848f000000b002de9e315011mr2537185ljh.24.1714035424954; Thu, 25 Apr 2024 01:57:04 -0700 (PDT) Received: from ?IPV6:2003:cb:c719:8200:487a:3426:a17e:d7b7? (p200300cbc7198200487a3426a17ed7b7.dip0.t-ipconnect.de. [2003:cb:c719:8200:487a:3426:a17e:d7b7]) by smtp.gmail.com with ESMTPSA id m25-20020a05600c3b1900b0041816c3049csm26789079wms.11.2024.04.25.01.57.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Apr 2024 01:57:04 -0700 (PDT) Message-ID: Date: Thu, 25 Apr 2024 10:57:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/5] add mTHP support for anonymous share pages To: Ryan Roberts , Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ying.huang@intel.com, shy828301@gmail.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <4b998e7d-153f-48cc-a9bb-8c84bb675581@arm.com> <80b5f87e-c156-4ccc-98f0-96f1fd864273@arm.com> <5b8b22e7-6355-4b08-b5b5-1e33ebae6f16@arm.com> <813fe7fd-3004-4e8b-801d-95c33559a025@linux.alibaba.com> <76f816dd-3bbf-48c9-a630-3787051cf289@arm.com> <8c0d6358-3c16-4a57-822c-04b3b3403fe6@linux.alibaba.com> <4204b5f6-21f0-4aa2-a625-3dd2f416b649@arm.com> <94ae96f7-79ce-4b3f-a272-6af62d01a3f8@redhat.com> <71c1e953-84f9-4d47-bd4c-725a447627df@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <71c1e953-84f9-4d47-bd4c-725a447627df@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: jrg6bgxt51wzo1qi4ioj7dnjcur5gaac X-Rspamd-Queue-Id: 73D5210000F X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1714035429-271314 X-HE-Meta: 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 N6re1Ttm Rbet680vwvILzUxva9wNN5dYcSI0bnE1A8A2HGmnyT6ED2z+/LlViIXCQ9I75PqMPxZvpu6fTpkwmaZO63fdX1sW42KFU62S4P4zh6b6yMBRtFa9owFkGu/dJkne63jmEmg4Jly9ZB2gZyubAPPfT7TWpDdp7jQk4fDnhDNE0VFjOWF7s6UB0ct7vY/rnDnLnK4LUqRVRZI2nnuWqopqay9gEKAZ01T/t9ci+BPPlAH2mDK4gq4hKUb5INnLQuglV1HtzvQ6j26FO2EebmZCOOqPWxLR7rf5ZFvq7ylduha5FuRxvMh7FwiOPNz+Ft2P/bHt9KrRnub0cxK3Vi9XAYM1cYeh0Z89ZHBKkLupBQsITbE/HaLZo0iYSis9oeq2x9FMHJea6zGy+olD41aVH/UD3DkVaNUpXp/X3my7JB4ovXA0qsbWP8hs9lLD8/qOYaDtnoUJWF1lUZlL83qsGDOub0sIAJrwkfetp 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 25.04.24 10:46, Ryan Roberts wrote: > On 25/04/2024 09:26, David Hildenbrand wrote: >> On 25.04.24 10:17, Ryan Roberts wrote: >>> On 25/04/2024 07:20, Baolin Wang wrote: >>>> >>>> >>>> On 2024/4/24 22:20, Ryan Roberts wrote: >>>>> On 24/04/2024 14:49, Baolin Wang wrote: >>>>>> >>>>>> >>>>>> On 2024/4/24 18:01, Ryan Roberts wrote: >>>>>>> On 24/04/2024 10:55, Baolin Wang wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 2024/4/24 16:26, Ryan Roberts wrote: >>>>>>>>> On 24/04/2024 07:55, Baolin Wang wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On 2024/4/23 18:41, Ryan Roberts wrote: >>>>>>>>>>> On 22/04/2024 08:02, Baolin Wang wrote: >>>>>>>>>>>> Anonymous pages have already been supported for multi-size (mTHP) >>>>>>>>>>>> allocation >>>>>>>>>>>> through commit 19eaf44954df, that can allow THP to be configured >>>>>>>>>>>> through the >>>>>>>>>>>> sysfs interface located at >>>>>>>>>>>> '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'. >>>>>>>>>>>> >>>>>>>>>>>> However, the anonymous shared pages will ignore the anonymous mTHP rule >>>>>>>>>>>> configured through the sysfs interface, and can only use the PMD-mapped >>>>>>>>>>>> THP, that is not reasonable. Many implement anonymous page sharing >>>>>>>>>>>> through >>>>>>>>>>>> mmap(MAP_SHARED | MAP_ANONYMOUS), especially in database usage >>>>>>>>>>>> scenarios, >>>>>>>>>>>> therefore, users expect to apply an unified mTHP strategy for anonymous >>>>>>>>>>>> pages, >>>>>>>>>>>> also including the anonymous shared pages, in order to enjoy the >>>>>>>>>>>> benefits of >>>>>>>>>>>> mTHP. For example, lower latency than PMD-mapped THP, smaller memory >>>>>>>>>>>> bloat >>>>>>>>>>>> than PMD-mapped THP, contiguous PTEs on ARM architecture to reduce TLB >>>>>>>>>>>> miss >>>>>>>>>>>> etc. >>>>>>>>>>> >>>>>>>>>>> This sounds like a very useful addition! >>>>>>>>>>> >>>>>>>>>>> Out of interest, can you point me at any workloads (and off-the-shelf >>>>>>>>>>> benchmarks >>>>>>>>>>> for those workloads) that predominantly use shared anon memory? >>>>>>>>>> >>>>>>>>>> As far as I know, some database related workloads make extensive use of >>>>>>>>>> shared >>>>>>>>>> anonymous page, such as PolarDB[1] in our Alibaba fleet, or MySQL likely >>>>>>>>>> also >>>>>>>>>> uses shared anonymous memory. And I still need to do some investigation to >>>>>>>>>> measure the performance. >>>>>>>>>> >>>>>>>>>> [1] https://github.com/ApsaraDB/PolarDB-for-PostgreSQL >>>>>>>>> >>>>>>>>> Thanks for the pointer! >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>> The primary strategy is that, the use of huge pages for anonymous shared >>>>>>>>>>>> pages >>>>>>>>>>>> still follows the global control determined by the mount option "huge=" >>>>>>>>>>>> parameter >>>>>>>>>>>> or the sysfs interface at >>>>>>>>>>>> '/sys/kernel/mm/transparent_hugepage/shmem_enabled'. >>>>>>>>>>>> The utilization of mTHP is allowed only when the global 'huge' switch is >>>>>>>>>>>> enabled. >>>>>>>>>>>> Subsequently, the mTHP sysfs interface >>>>>>>>>>>> (/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled) >>>>>>>>>>>> is checked to determine the mTHP size that can be used for large folio >>>>>>>>>>>> allocation >>>>>>>>>>>> for these anonymous shared pages. >>>>>>>>>>> >>>>>>>>>>> I'm not sure about this proposed control mechanism; won't it break >>>>>>>>>>> compatibility? I could be wrong, but I don't think shmem's use of THP >>>>>>>>>>> used to >>>>>>>>>>> depend upon the value of /sys/kernel/mm/transparent_hugepage/enabled? >>>>>>>>>>> So it >>>>>>>>>> >>>>>>>>>> Yes, I realized this after more testing. >>>>>>>>>> >>>>>>>>>>> doesn't make sense to me that we now depend upon the >>>>>>>>>>> /sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled values >>>>>>>>>>> (which by >>>>>>>>>>> default disables all sizes except 2M, which is set to "inherit" from >>>>>>>>>>> /sys/kernel/mm/transparent_hugepage/enabled). >>>>>>>>>>> >>>>>>>>>>> The other problem is that shmem_enabled has a different set of options >>>>>>>>>>> (always/never/within_size/advise/deny/force) to enabled >>>>>>>>>>> (always/madvise/never) >>>>>>>>>>> >>>>>>>>>>> Perhaps it would be cleaner to do the same trick we did for enabled; >>>>>>>>>>> Introduce >>>>>>>>>>> /mm/transparent_hugepage/hugepage-XXkb/shmem_enabled, which can have all >>>>>>>>>>> the >>>>>>>>>>> same values as the top-level >>>>>>>>>>> /sys/kernel/mm/transparent_hugepage/shmem_enabled, >>>>>>>>>>> plus the additional "inherit" option. By default all sizes will be set to >>>>>>>>>>> "never" except 2M, which is set to "inherit". >>>>>>>>>> >>>>>>>>>> Sounds good to me. But I do not want to copy all same values from >>>>>>>>>> top-level >>>>>>>>>> '/sys/kernel/mm/transparent_hugepage/shmem_enabled': >>>>>>>>>> always within_size advise never deny force >>>>>>>>>> >>>>>>>>>> For mTHP's shmem_enabled interface, we can just keep below values: >>>>>>>>>> always within_size advise never >>>>>>>>>> >>>>>>>>>> Cause when checking if mTHP can be used for anon shmem, 'deny' is equal to >>>>>>>>>> 'never', and 'force' is equal to 'always'. >>>>>>>>> >>>>>>>>> I'll admit it wasn't completely clear to me after reading the docs, but my >>>>>>>>> rough >>>>>>>>> understanding is: >>>>>>>>> >>>>>>>>>      - /sys/kernel/mm/transparent_hugepage/shmem_enabled controls >>>>>>>>>        mmap(SHARED|ANON) allocations (mostly; see rule 3) >>>>>>>>>      - huge=... controls tmpfs allocations >>>>>>>>>      - deny and force in shmem_enabled are equivalent to never and >>>>>>>>> always for >>>>>>>>>        mmap(SHARED|ANON) but additionally override all tmpfs mounts so they >>>>>>>>> act as >>>>>>>>>        if they were mounted with huge=never or huge=always >>>>>>>>> >>>>>>>>> Is that correct? If so, then I think it still makes sense to support >>>>>>>>> per-size >>>>>>>> >>>>>>>> Correct. >>>>>>>> >>>>>>>>> deny/force. Certainly if a per-size control is set to "inherit" and the >>>>>>>>> top-level control is set to deny or force, you would need that to mean >>>>>>>>> something. >>>>>>>> >>>>>>>> IMHO, the '/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled' interface >>>>>>>> should only control the anonymous shmem. And 'huge=' controls tmpfs >>>>>>>> allocation, >>>>>>>> so we should not use anonymous control to override tmpfs control, which >>>>>>>> seems a >>>>>>>> little mess? >>>>>>> >>>>>>> I agree it would be cleaner to only handle mmap(SHARED|ANON) here, and leave >>>>>>> the >>>>>>> tmpfs stuff for another time. But my point is that >>>>>>> /mm/transparent_hugepage/shmem_enabled already interferes with tmpfs if the >>>>>>> value is deny or force. So if you have: >>>>>>> >>>>>>> echo deny > /mm/transparent_hugepage/shmem_enabled >>>>>> >>>>>> IIUC, this global control will cause shmem_is_huge() to always return >>>>>> false, so >>>>>> no matter how '/mm/transparent_hugepage/hugepage-xxxkB/shmem_enabled' is set, >>>>>> anonymous shmem will not use mTHP. No? >>>>> >>>>> No, that's not how '/mm/transparent_hugepage/hugepage-xxxkB/enabled' works, and >>>>> I think '/mm/transparent_hugepage/hugepage-xxxkB/shmem_enabled' should follow >>>>> the established pattern. >>>>> >>>>> For anon-private, each size is controlled by its >>>>> /mm/transparent_hugepage/hugepage-xxxkB/enabled value. Unless that value is >>>>> "inherit", in which case the value in /mm/transparent_hugepage/enabled is used >>>>> for that size. >>>>> >>>>> That approach enables us to 1) maintain back-compat and 2) control each size >>>>> independently >>>>> >>>>> 1) is met because the default is that all sizes are initially set to "never", >>>>> except the PMD-size (e.g. /mm/transparent_hugepage/hugepage-2048kB/enabled) >>>>> which is initially set to inherit. So any mTHP unaware SW can still modify >>>>> /mm/transparent_hugepage/enabled and it will still only apply to PMD size. >>>>> >>>>> 2) is met because mTHP aware SW can come along and e.g. enable the 64K size >>>>> (echo always > /mm/transparent_hugepage/hugepage-64kB/enabled) without >>>>> having to >>>>> modify the value in /mm/transparent_hugepage/enabled. >>>> >>>> Thanks for explanation. Initially, I want to make >>>> ‘/mm/transparent_hugepage/shmem_enabled’ be a global control for huge page, but >>>> I think it should follow the same strategy as anon mTHP as you said. >>>> >>>>>>> echo inherit > /mm/transparent_hugepage/hugepage-64kB/shmem_enabled >>>>>>> >>>>>>> What does that mean? >>>>> >>>>> So I think /mm/transparent_hugepage/hugepage-xxxkB/shmem_enabled will need to >>>>> support the deny and force values. When applied to non-PMD sizes, "deny" can >>>>> just be a noop for now, because there was no way to configure a tmpfs mount for >>>>> non-PMD size THP in the first place. But I'm not sure what to do with "force"? >>>> >>>> OK. And I also prefer that "force" should be a noop too, since anon shmem >>>> control should not configure tmpfs huge page allocation. >>> >>> I guess technically they won't be noops, but (for the non-PMD-sizes) "force" >>> will be an alias for "always" and "deny" will be an alias for "never"? >>> >>> I was just a bit concerned about later changing that behavior to also impact >>> tmpfs once tmpfs supports mTHP; could that cause breaks? But thinking about it, >>> I don't see that as a problem. >> >> Is the question what should happen if we "inherit" "force" or if someone >> specifies "force" for a mTP size explicitly? > > Well I think it amounts to the same thing; there isn't much point in forbidding > "force" to be set directly because it can still be set indirectly through > "inherit". We can't forbid indirectly setting it, because "inherit" could be set > first, then the top-level shmem_enabled changed to "force" after - and we > wouldn't want to fail that. The default for PMD should be "inherit", for the other mTHP sizes it should be "never". So we should fail if: * Setting top-level to "force" when any non-PMD size is "inherit" * Setting "inherit" of a non-PMD size when the top-level is force Both will only happen if someone messes with the mTHP configuration manually. And we should only offer "force" as an option for PMD-sized mTHP as long as the others are not supported. See below. > > So I think the question is just 'what should happen when "force" is configured > for a non-PMD-sized mTHP'? We should hide it and not offer a configuration toggle that is inactive. If someone wants to sense support for other mTHP "force" settings in the future, they can just parse if the "shmem_enabled" toggle offers "force" as an option. Then they know that it can actually be enabled and will also do what is promised. -- Cheers, David / dhildenb