From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9AF571E1051 for ; Wed, 30 Oct 2024 08:34:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730277300; cv=none; b=DO0EDfTTkIZ2L5QD1bVi2MQ5tuYjlN/q72PW4RXxl9IWpdSUQAjVNgjtLuMT1MANzUrpKEOTk9c5Nga5f2XIExk/o1Ab6W7MuioYnfU9mcfnBWfclPq/0ZBRDR8xv/7SA0dTvZmiysEuMOS+v3B6Ti125hdUh+2CnMQ/f3zVowY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730277300; c=relaxed/simple; bh=zlos3ROi5kzEr1HCIe3QhChCav3Kh2ANxKv9HThCPcY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NwpMoLyeoEncIwUs1UqfhD1Sgp+NukL7QWxv0og8D47nWvDhtpuuY4dGg1fBFYZyeQ+ROP5yzaQcIC+jan+rTp3UCYT2ormoejYODxHnfxmb+/1JxFEhIK1NCDwt+mVqm3ceScDxYUy2yVE5TyLAYTV/7iUIh6wKfhuvdxwfYDY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=GM+N4L0y; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GM+N4L0y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730277297; 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=RDbKspYQEPtAp9PIc46oWA+G9yo3CZRa6RrJLEqMKK8=; b=GM+N4L0yaejNVSMeAxw258zFzBH1+rJ0DHdjbFrdGhyUgn6XuJAifXH8J16pU33qUnWuHm AVUOkQAj/mIlWLiq9+kdSc4uyjtsv8amZRlZ4E3yZjFzG6nCRBPNQGlSs8Yq1LDBn1vOdh Oegix0TjMBbZt5TOR8w8q3qBBoumg/Q= 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-125-VcIKvQHfOAyF0vUZ5Cx42g-1; Wed, 30 Oct 2024 04:34:56 -0400 X-MC-Unique: VcIKvQHfOAyF0vUZ5Cx42g-1 Received: by mail-lj1-f199.google.com with SMTP id 38308e7fff4ca-2fb44181f04so41574011fa.2 for ; Wed, 30 Oct 2024 01:34:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730277295; x=1730882095; 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=RDbKspYQEPtAp9PIc46oWA+G9yo3CZRa6RrJLEqMKK8=; b=fOyaerSiYA5mCvhbxyuBJQSzB7J7x6Y5UmrxGbbt1O8iMIdsh8cUuaOXm9Tyx9XFhP d7xvJMHl2+nLtkocM2qj2LVyABsYhiX4WoX4m5ay/r3ojQ32OvuXLfJgG+mnHUArKlNg vb7OOKa1xMweNISpL2VZbJbecfyfX2crIhId1Ps2BeZHl5WJ9U3k+Vlhu3sqBte6qhP3 4etnQ9Zdh4y6g4v+CKFXmwZyKKVHxOX+pRIKZO7KhG19wk9IhyVGI5coB11wFqKCIDab RJU+lAiq7LRVj68z5GrBmzOmBQANTCML55jSqdOI7DbUBMiuJshUI9tQnwhUldYg0MiS jP4Q== X-Forwarded-Encrypted: i=1; AJvYcCWrSUxF638QfIluHg/YNMy/TP3DDExLogQHK6X8Scgb5+X3mbSVsDLS2rR672LLkQuN0bJwpEJSk0eI2JE=@vger.kernel.org X-Gm-Message-State: AOJu0YyDMlMjydlQ80fQGIH7LNlEh/kx5Axrof8QL/71Gu1GnmJyx1DP Nek5uu85QB+vPNH/OZlh4WfSpVZOEPDtXl+HwLpCJ5WkuVsGIUfhB3fPDiHoFAz7Vjryz2es4ya +HJ1Ub3bN6bRPe93n+J++BRxu4SUYUVvx0sc+6TTO//hvLXNv0xVQUk+nCdFzvA== X-Received: by 2002:a2e:b8c8:0:b0:2fb:6229:c597 with SMTP id 38308e7fff4ca-2fcbdf5fcf8mr69187091fa.4.1730277294593; Wed, 30 Oct 2024 01:34:54 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEUqXHjWrf0yZc8HqI1EVnYphaEAFWk18vOTEaTr/lQjC8GHkjp05lhb0SF6NZzZNrXwD2/yQ== X-Received: by 2002:a2e:b8c8:0:b0:2fb:6229:c597 with SMTP id 38308e7fff4ca-2fcbdf5fcf8mr69186921fa.4.1730277294132; Wed, 30 Oct 2024 01:34:54 -0700 (PDT) Received: from ?IPV6:2003:cb:c733:7c00:d067:e327:4f99:7546? (p200300cbc7337c00d067e3274f997546.dip0.t-ipconnect.de. [2003:cb:c733:7c00:d067:e327:4f99:7546]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-431bd990dc1sm14201265e9.40.2024.10.30.01.34.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Oct 2024 01:34:52 -0700 (PDT) Message-ID: Date: Wed, 30 Oct 2024 09:34:51 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/gup: restore the ability to pin more than 2GB at a time To: John Hubbard , Alistair Popple Cc: Christoph Hellwig , Andrew Morton , LKML , linux-mm@kvack.org, linux-stable@vger.kernel.org, Vivek Kasireddy , Dave Airlie , Gerd Hoffmann , Matthew Wilcox , Jason Gunthorpe , Peter Xu , Arnd Bergmann , Daniel Vetter , Dongwon Kim , Hugh Dickins , Junxiao Chang , Mike Kravetz , Oscar Salvador References: <20241030030116.670307-1-jhubbard@nvidia.com> <249d2614-0bcc-4ca8-b24e-7c0578a81dce@nvidia.com> <87r07yp0ng.fsf@nvdebian.thelocal> <128d04dd-2d48-4a98-8537-49589b4db1c3@nvidia.com> From: David Hildenbrand Content-Language: en-US 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: <128d04dd-2d48-4a98-8537-49589b4db1c3@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 30.10.24 07:50, John Hubbard wrote: > On 10/29/24 11:18 PM, Alistair Popple wrote: >> John Hubbard writes: >>> On 10/29/24 9:42 PM, Christoph Hellwig wrote: >>>> On Tue, Oct 29, 2024 at 09:39:15PM -0700, John Hubbard wrote: > ... >>>> Because pinning down these amounts of memoryt is completely insane. >>>> I don't mind the switch to kvmalloc, but we need to put in an upper >>>> bound of what can be pinned. >>> >>> I'm wondering though, how it is that we decide how much of the user's >>> system we prevent them from using? :) People with hardware accelerators >>> do not always have page fault capability, and yet these troublesome >>> users insist on stacking their system full of DRAM and then pointing >>> the accelerator to it. >>> >>> How would we choose a value? Memory sizes keep going up... >> >> The obvious answer is you let users decide. I did have a patch series to >> do that via a cgroup[1]. However I dropped that series mostly because I >> couldn't find any users of such a limit to provide feedback on how they >> would use it or how they wanted it to work. >> > > Trawling through the discussion there, I see that Jason Gunthorpe mentioned: > > "Things like VFIO & KVM use cases effectively pin 90% of all system memory" The unusual thing is not the amount of system memory we are pinning but *how many* pages we try pinning in the single call. If you stare at vfio_pin_pages_remote, we seem to be batching it. long req_pages = min_t(long, npage, batch->capacity); Which is #define VFIO_BATCH_MAX_CAPACITY (PAGE_SIZE / sizeof(struct page *)) So you can fix this in your driver ;) We should maybe try a similar limit internally: if you call pin_user_pages_remote() with a large number, we'll cap it at some magic value (similar to above). The caller will simply realize that not all pages were pinned and will retry. See get_user_pages_remote(): "Returns either number of pages pinned (which may be less than the number requested), or an error. Details about the return value:" Alternatively, I recall there was a way to avoid the temporary allocation ... let me hack up a prototype real quick. -- Cheers, David / dhildenb