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 X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7232DC43461 for ; Tue, 8 Sep 2020 14:22:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D867822527 for ; Tue, 8 Sep 2020 14:22:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Wq6eqkpN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D867822527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 350496B0055; Tue, 8 Sep 2020 10:22:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2FF8C6B005A; Tue, 8 Sep 2020 10:22:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1C7D36B005C; Tue, 8 Sep 2020 10:22:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0064.hostedemail.com [216.40.44.64]) by kanga.kvack.org (Postfix) with ESMTP id 055526B0055 for ; Tue, 8 Sep 2020 10:22:25 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id BF1DA180AD802 for ; Tue, 8 Sep 2020 14:22:24 +0000 (UTC) X-FDA: 77240109408.02.pear16_2c00bd8270d5 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 790E4100B215F for ; Tue, 8 Sep 2020 14:22:24 +0000 (UTC) X-HE-Tag: pear16_2c00bd8270d5 X-Filterd-Recvd-Size: 9220 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Tue, 8 Sep 2020 14:22:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599574943; 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=4kpP9XU0+UuUolyV891ejphwy2iWWA+w3mapvFltoqQ=; b=Wq6eqkpNfAP1FZYYxyBsx+dT/huSudbOHlFN9QaJXEoVAoNwdbgxWvDdjfg7wN/j5ejis0 G+QaeWGr0nQnBUhTomqunkuZgo/JLtuuJDe6CSBC8fi69Ko/U6+xCmuCC4i6ireLs1wwXh b8V2AY1jNrP4+dWvXycr/urXcXaftKo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-537-cDJyKfWiMiKkwKb5iKQU2Q-1; Tue, 08 Sep 2020 10:22:16 -0400 X-MC-Unique: cDJyKfWiMiKkwKb5iKQU2Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5DF0B10ABDA1; Tue, 8 Sep 2020 14:22:14 +0000 (UTC) Received: from [10.36.115.46] (ovpn-115-46.ams2.redhat.com [10.36.115.46]) by smtp.corp.redhat.com (Postfix) with ESMTP id E9A917ED84; Tue, 8 Sep 2020 14:22:11 +0000 (UTC) Subject: Re: [RFC PATCH 00/16] 1GB THP support on x86_64 To: Zi Yan Cc: Roman Gushchin , "Kirill A. Shutemov" , linux-mm@kvack.org, Rik van Riel , "Kirill A . Shutemov" , Matthew Wilcox , Shakeel Butt , Yang Shi , David Nellans , linux-kernel@vger.kernel.org References: <20200902180628.4052244-1-zi.yan@sent.com> <20200903142300.bjq2um5y5nwocvar@box> <20200903163020.GG60440@carbon.dhcp.thefacebook.com> <8e677ead-206d-08dd-d73e-569bd3803e3b@redhat.com> <7E20392E-5ED7-4C22-9555-F3BAABF3CBE9@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW 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/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/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 GmbH Message-ID: <32e979c4-68c0-f309-d9d7-d274724bd23e@redhat.com> Date: Tue, 8 Sep 2020 16:22:11 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <7E20392E-5ED7-4C22-9555-F3BAABF3CBE9@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Rspamd-Queue-Id: 790E4100B215F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable 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: On 08.09.20 16:05, Zi Yan wrote: > On 8 Sep 2020, at 7:57, David Hildenbrand wrote: >=20 >> On 03.09.20 18:30, Roman Gushchin wrote: >>> On Thu, Sep 03, 2020 at 05:23:00PM +0300, Kirill A. Shutemov wrote: >>>> On Wed, Sep 02, 2020 at 02:06:12PM -0400, Zi Yan wrote: >>>>> From: Zi Yan >>>>> >>>>> Hi all, >>>>> >>>>> This patchset adds support for 1GB THP on x86_64. It is on top of >>>>> v5.9-rc2-mmots-2020-08-25-21-13. >>>>> >>>>> 1GB THP is more flexible for reducing translation overhead and incr= easing the >>>>> performance of applications with large memory footprint without app= lication >>>>> changes compared to hugetlb. >>>> >>>> This statement needs a lot of justification. I don't see 1GB THP as = viable >>>> for any workload. Opportunistic 1GB allocation is very questionable >>>> strategy. >>> >>> Hello, Kirill! >>> >>> I share your skepticism about opportunistic 1 GB allocations, however= it might be useful >>> if backed by an madvise() annotations from userspace application. In = this case, >>> 1 GB THPs might be an alternative to 1 GB hugetlbfs pages, but with a= more convenient >>> interface. >> >> I have concerns if we would silently use 1~GB THPs in most scenarios >> where be would have used 2~MB THP. I'd appreciate a trigger to >> explicitly enable that - MADV_HUGEPAGE is not sufficient because some >> applications relying on that assume that the THP size will be 2~MB >> (especially, if you want sparse, large VMAs). >=20 > This patchset is not intended to silently use 1GB THP in place of 2MB T= HP. > First of all, there is a knob /sys/kernel/mm/transparent_hugepage/enabl= e_1GB > to enable 1GB THP explicitly. Also, 1GB THP is allocated from a reserve= d CMA > region (although I had alloc_contig_pages as a fallback, which can be r= emoved > in next version), so users need to add hugepage_cma=3DnG kernel paramet= er to > enable 1GB THP allocation. If a finer control is necessary, we can add > a new MADV_HUGEPAGE_1GB for 1GB THP. Thanks for the information - I would have loved to see important information like that (esp. how to use) in the cover letter. So what you propose is (excluding alloc_contig_pages()) really just automatically using (previously reserved) 1GB huge pages as 1GB THP instead of explicitly using them in an application using hugetlbfs. Still, not convinced how helpful that actually is - most certainly you really want a mechanism to control this per application (+ maybe make the application indicate actual ranges where it makes sense - but then you can directly modify the application to use hugetlbfs). I guess the interesting thing of this approach is that we can mix-and-match THP of differing granularity within a single mapping - whereby a hugetlbfs allocation would fail in case there isn't sufficient 1GB pages available. However, there are no guarantees for applications anymore (thinking about RT KVM and similar, we really want gigantic pages and cannot tolerate falling back to smaller granularity). What are intended use cases/applications that could benefit? I doubt databases and virtualization are really a good fit - they know how to handle hugetlbfs just fine. --=20 Thanks, David / dhildenb