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=-4.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,LH_URI_DOM_IN_PATH, 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 E0C89C47095 for ; Mon, 5 Oct 2020 18:33:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5BF8220853 for ; Mon, 5 Oct 2020 18:33:59 +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="fzE9/l4m" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BF8220853 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 97720900016; Mon, 5 Oct 2020 14:33:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8FFFF90000C; Mon, 5 Oct 2020 14:33:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7A1AB900016; Mon, 5 Oct 2020 14:33:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0235.hostedemail.com [216.40.44.235]) by kanga.kvack.org (Postfix) with ESMTP id 4B73290000C for ; Mon, 5 Oct 2020 14:33:58 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id DAD8E181AE870 for ; Mon, 5 Oct 2020 18:33:57 +0000 (UTC) X-FDA: 77338720914.26.wave43_1f0edeb271c0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 09F831804B669 for ; Mon, 5 Oct 2020 18:33:56 +0000 (UTC) X-HE-Tag: wave43_1f0edeb271c0 X-Filterd-Recvd-Size: 11603 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Mon, 5 Oct 2020 18:33:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601922835; 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=zZSWnSFyk7MS3PaY/M4AEA2+8yQ+I+LXHl1znh3Du24=; b=fzE9/l4mHVVk10yKe+0lg7UqzqNgEjN3bXazrqHsou4XEXcm+QuYf9B53wFAq6iZQJmqGt sNqF22V9menBwwiftSpPcK+TfW7btdrV+XbZt0fRfzMFuxOUnAesrhBl7bmNB5O+p76uOS oqa92BrAgBkq5RHOIm3BNTpe6+Ac8f8= 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-312-Lq6JpqSsP7qcGOd1j95joQ-1; Mon, 05 Oct 2020 14:33:51 -0400 X-MC-Unique: Lq6JpqSsP7qcGOd1j95joQ-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 AA35618C5201; Mon, 5 Oct 2020 18:33:48 +0000 (UTC) Received: from [10.36.112.79] (ovpn-112-79.ams2.redhat.com [10.36.112.79]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2C0339CBA; Mon, 5 Oct 2020 18:33:45 +0000 (UTC) Subject: Re: [RFC PATCH v2 00/30] 1GB PUD THP support on x86_64 To: Roman Gushchin Cc: Zi Yan , Michal Hocko , linux-mm@kvack.org, "Kirill A . Shutemov" , Rik van Riel , Matthew Wilcox , Shakeel Butt , Yang Shi , Jason Gunthorpe , Mike Kravetz , William Kucharski , Andrea Arcangeli , John Hubbard , David Nellans , linux-kernel@vger.kernel.org References: <20200928175428.4110504-1-zi.yan@sent.com> <20200930115505.GT2277@dhcp22.suse.cz> <73394A41-16D8-431C-9E48-B14D44F045F8@nvidia.com> <20201002073205.GC20872@dhcp22.suse.cz> <9a7600e2-044a-50ca-acde-bf647932c751@redhat.com> <20201002081023.GA4555@dhcp22.suse.cz> <645b35a5-970d-dcfe-2b4a-04ebd4444756@redhat.com> <20201005171632.GB2990415@carbon.DHCP.thefacebook.com> <20201005182518.GA3001706@carbon.dhcp.thefacebook.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: <824eee1c-a47b-361b-ad5b-6ed64a9cbd38@redhat.com> Date: Mon, 5 Oct 2020 20:33:44 +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: <20201005182518.GA3001706@carbon.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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 05.10.20 20:25, Roman Gushchin wrote: > On Mon, Oct 05, 2020 at 07:27:47PM +0200, David Hildenbrand wrote: >> On 05.10.20 19:16, Roman Gushchin wrote: >>> On Mon, Oct 05, 2020 at 11:03:56AM -0400, Zi Yan wrote: >>>> On 2 Oct 2020, at 4:30, David Hildenbrand wrote: >>>> >>>>> On 02.10.20 10:10, Michal Hocko wrote: >>>>>> On Fri 02-10-20 09:50:02, David Hildenbrand wrote: >>>>>>>>>> - huge page sizes controllable by the userspace? >>>>>>>>> >>>>>>>>> It might be good to allow advanced users to choose the page siz= es, so they >>>>>>>>> have better control of their applications. >>>>>>>> >>>>>>>> Could you elaborate more? Those advanced users can use hugetlb, = right? >>>>>>>> They get a very good control over page size and pool preallocati= on etc. >>>>>>>> So they can get what they need - assuming there is enough memory= . >>>>>>>> >>>>>>> >>>>>>> I am still not convinced that 1G THP (TGP :) ) are really what we= want >>>>>>> to support. I can understand that there are some use cases that m= ight >>>>>>> benefit from it, especially: >>>>>> >>>>>> Well, I would say that internal support for larger huge pages (e.g= . 1GB) >>>>>> that can transparently split under memory pressure is a useful >>>>>> funtionality. I cannot really judge how complex that would be >>>>> >>>>> Right, but that's then something different than serving (scarce, >>>>> unmovable) gigantic pages from CMA / reserved hugetlbfs pool. Nothi= ng >>>>> wrong about *real* THP support, meaning, e.g., grouping consecutive >>>>> pages and converting them back and forth on demand. (E.g., 1GB -> >>>>> multiple 2MB -> multiple single pages), for example, when having to >>>>> migrate such a gigantic page. But that's very different from our >>>>> existing gigantic page code as far as I can tell. >>>> >>>> Serving 1GB PUD THPs from CMA is a compromise, since we do not want = to >>>> bump MAX_ORDER to 20 to enable 1GB page allocation in buddy allocato= r, >>>> which needs section size increase. In addition, unmoveable pages can= not >>>> be allocated in CMA, so allocating 1GB pages has much higher chance = from >>>> it than from ZONE_NORMAL. >>> >>> s/higher chances/non-zero chances >> >> Well, the longer the system runs (and consumes a significant amount of >> available main memory), the less likely it is. >> >>> >>> Currently we have nothing that prevents the fragmentation of the memo= ry >>> with unmovable pages on the 1GB scale. It means that in a common case >>> it's highly unlikely to find a continuous GB without any unmovable pa= ge. >>> As now CMA seems to be the only working option. >>> >> >> And I completely dislike the use of CMA in this context (for example, >> allocating via CMA and freeing via the buddy by patching CMA when >> splitting up PUDs ...). >> >>> However it seems there are other use cases for the allocation of cont= inuous >>> 1GB pages: e.g. secretfd ( https://urldefense.proofpoint.com/v2/url?u= =3Dhttps-3A__lwn.net_Articles_831628_&d=3DDwIDaQ&c=3D5VD0RTtNlTh3ycd41b3M= Uw&r=3DjJYgtDM7QT-W-Fz_d29HYQ&m=3DmdcwiGna7gQ4-RC_9XdaxFZ271PEQ09M0YtCcRo= Ckf8&s=3D4KlK2p0AVh1QdL8XDVeWyXPz4F63pdbbSCoxQlkNaa4&e=3D ), where using >>> 1GB pages can reduce the fragmentation of the direct mapping. >> >> Yes, see RFC v1 where I already cced Mike. >> >>> >>> So I wonder if we need a new mechanism to avoid fragmentation on 1GB/= PUD scale. >>> E.g. something like a second level of pageblocks. That would allow to= group >>> all unmovable memory in few 1GB blocks and have more 1GB regions avai= lable for >>> gigantic THPs and other use cases. I'm looking now into how it can be= done. >> >> Anything bigger than sections is somewhat problematic: you have to tra= ck >> that data somewhere. It cannot be the section (in contrast to pagebloc= ks) >=20 > Well, it's not a large amount of data: the number of 1GB regions is not= that > high even on very large machines. Yes, but then you can have very sparse systems. And some use cases would actually want to avoid fragmentation on smaller levels (e.g., 128MB) - optimizing memory efficiency by turning off banks and such ... >=20 >> >>> If anybody has any ideas here, I'll appreciate a lot. >> >> I already brought up the idea of ZONE_PREFER_MOVABLE (see RFC v1). Tha= t >> somewhat mimics what CMA does (when sized reasonably), works well with >> memory hot(un)plug, and is immune to misconfiguration. Within such a >> zone, we can try to optimize the placement of larger blocks. >=20 > Thank you for pointing at it! >=20 > The main problem with it is the same as with ZONE_MOVABLE: it does requ= ire > a boot-time educated guess on a good size. I admit that the CMA does to= o. "Educated guess" of ratios like 1:1. 1:2, and even 1:4 (known from highmem times) ares usually perfectly fine. And if you mess up - in comparison to CMA - you won't shoot yourself in the foot, you get less gigantic pages - which is usually better than before. I consider that a clear win. Perfect? No. Can we be perfect? unlikely. In comparison to CMA / ZONE_MOVABLE, a bad guess won't cause instabilitie= s. --=20 Thanks, David / dhildenb