From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 78E811B4C23 for ; Mon, 28 Oct 2024 09:48:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730108932; cv=none; b=X5Wn77cJqSxYRXCogWD/S6E5pl8x/Ak3FSBHVEYtksrglHoslJFP2/1flphRVy9NK9P+j0+cMeIdhPbBOXy4rB844+KOfJVHvAt+8td6ne1zbCKk+5L1tik47CviTbCIqTDNT3WgpKCuH/pt4f3DmH01JoBL0IqQ5bwDbVhTHaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730108932; c=relaxed/simple; bh=FQj3S1PJRVwAsgeE2gJ/qqEKLhrs9AAygGNJaqvKB7I=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=exSsb56hvolcnaWAkmFzvaCRN/OE+kAXvYQBJqmdxHU58RVutN1FSJGHgKKhFP9AU9LXnZqY1NnaeX2i+po151k+gDQHE5q4eiIDy+NDHiXiVPa7GbXUcrYlsVjJ3noVc7mIRJsuVTQInSR5+45kQHn5VNRki+3v1FLuu6K9XxI= 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=Iah17rPK; arc=none smtp.client-ip=170.10.133.124 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="Iah17rPK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730108929; 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=b5zLY75SeOz+vX8IBwgnxl+5DpkitlpkKm4uVYKjbxE=; b=Iah17rPK14HMkXTqgYiCvcLaLOFIztj2rlbyqjhG8+sEyZYKmxcrLhIV5/sqzCDZgTioH+ 6cb87AFqsSeYS6wjIrUNIDbeeQX5xEqeMpNMc6/cXcHZ99mAYDZAJxfoIYI6EGpCzeSDaE s4UIxFBmj5ELs7GEqi05M/0uTBbkhCE= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-692-zQjqgT11NOuMJHuOfpM3EA-1; Mon, 28 Oct 2024 05:48:47 -0400 X-MC-Unique: zQjqgT11NOuMJHuOfpM3EA-1 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-37d4cf04be1so1979040f8f.2 for ; Mon, 28 Oct 2024 02:48:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730108926; x=1730713726; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:references:cc:to:from:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=b5zLY75SeOz+vX8IBwgnxl+5DpkitlpkKm4uVYKjbxE=; b=m0XRDrTV1ky/JdBMaFt/3NqR53gZK/G/sHkMGY92/9rsKkQngZX470HdvrFRGCfi4u vwZ+M0Ji+2aCR4dlUVVCJp792aLtxaBJoQFpNRfQHoPtG6NBJT7y4z8K8v5VmQFY9pad bva8+XqRVN2d0QyQcCEqfFlucLv+Iu2+FhQ+vxBsOIrvjV+pLulvJHi9DuGeaFPjJ39H IvcbxJE9mopOUeVpDRJDKEm45y0QstK8rb2pFobVlqJGGkUABkpq1+liLiVhPuZj7PnM 9ldl8T9ymLYJzOdhYTHlhm9Kl4JlLkZsO0ZYJ6DtFhUiYHVXgdrLMGztVV9b7M86qePD 8Ebg== X-Forwarded-Encrypted: i=1; AJvYcCUfzIFwghD2ZfMa4D8Nz5YI3AdAvWe+87Y+FlYB9JhsUFOXMJj1txJcB6eX2eItwocDSYkfCHdJWIyPTHM=@vger.kernel.org X-Gm-Message-State: AOJu0YyYPjWhOfXlWeEpHEer64PJSn7SyLJnQiQFkSpMpcMkwqBT63bG dYcm+9yVvSMjDDhBMe2XhjhO7kwYXR5aKD+eVIL6CoAir2pfiRe2tQqIdACIzDJ5HFyN/F+Aeth zaPMdhDV+bVlzp0zR511cvNVC2/auI8vXjdF8ptJvTY1VfT3sWe6aw94ifs74pw== X-Received: by 2002:adf:a1cc:0:b0:37d:5129:f45e with SMTP id ffacd0b85a97d-380611433f5mr5483869f8f.20.1730108926665; Mon, 28 Oct 2024 02:48:46 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFOt2n+dP8wK3WpU/VMjWv2ws7V43qjZ5csjHr+yOUQkp8x86ZkMd987pqwf747f7iip4oIzA== X-Received: by 2002:adf:a1cc:0:b0:37d:5129:f45e with SMTP id ffacd0b85a97d-380611433f5mr5483853f8f.20.1730108926218; Mon, 28 Oct 2024 02:48:46 -0700 (PDT) Received: from ?IPV6:2a09:80c0:192:0:5dac:bf3d:c41:c3e7? ([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38058b47946sm9029551f8f.47.2024.10.28.02.48.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Oct 2024 02:48:45 -0700 (PDT) Message-ID: <7ca333ba-f9bc-4f78-8f5b-1035ca91c2d5@redhat.com> Date: Mon, 28 Oct 2024 10:48:44 +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: [RFC PATCH v3 0/4] Support large folios for tmpfs From: David Hildenbrand To: Daniel Gomez , Baolin Wang , Daniel Gomez , "Kirill A. Shutemov" Cc: Matthew Wilcox , akpm@linux-foundation.org, hughd@google.com, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ryan.roberts@arm.com, ioworker0@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" References: <6dohx7zna7x6hxzo4cwnwarep3a7rohx4qxubds3uujfb7gp3c@2xaubczl2n6d> <8e48cf24-83e1-486e-b89c-41edb7eeff3e@linux.alibaba.com> <486a72c6-5877-4a95-a587-2a32faa8785d@redhat.com> <7eb412d1-f90e-4363-8c7b-072f1124f8a6@linux.alibaba.com> <1b0f9f94-06a6-48ac-a68e-848bce1008e9@redhat.com> 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 25.10.24 22:21, David Hildenbrand wrote: > Sorry for the late reply! > >>>>>> IMHO, as I discussed with Kirill, we still need maintain compatibility >>>>>> with the 'huge=' mount option. This means that if 'huge=never' is set >>>>>> for tmpfs, huge page allocation will still be prohibited (which can >>>>>> address Hugh's request?). However, if 'huge=' is not set, we can >>>>>> allocate large folios based on the write size. >> >> So, in order to make tmpfs behave like other filesystems, we need to >> allocate large folios by default. Not setting 'huge=' is the same as >> setting it to 'huge=never' as per documentation. But 'huge=' is meant to >> control THP, not large folios, so it should not have a conflict here, or >> else, what case are you thinking? > > I think we really have to move away from "huge/thp == PMD", that's a > historical artifact. Everything else will simply be inconsistent and > confusing in the future -- and I don't see any real need for that. For > anonymous memory and anon shmem we managed the transition. (there is a > longer writeup from me about this topic, so I won't go into detail). > > > I think I raised this in the past, but tmpfs/shmem is just like any > other file system .. except it sometimes really isn't and behaves much > more like (swappable) anonymous memory. (or mlocked files) > > There are many systems out there that run without swap enabled, or with > extremely minimal swap (IIRC until recently kubernetes was completely > incompatible with swapping). Swap can even be disabled today for shmem > using a mount option. > > That's a big difference to all other file systems where you are > guaranteed to have backend storage where you can simply evict under > memory pressure (might temporarily fail, of course). > > I *think* that's the reason why we have the "huge=" parameter that also > controls the THP allocations during page faults (IOW possible memory > over-allocation). Maybe also because it was a new feature, and we only > had a single THP size. > > There is, of course also the "fallocate() might not free up memory if > there is an unexpected reference on the page because splitting it will > fail" problem, that even exists when not over-allocating memory in the > first place ... > > > So ...I don't think tmpfs behaves like other file system in some cases. > And I don't think ignoring these points is a good idea. > > Fortunately I don't maintain that code :) > > > If we don't want to go with the shmem_enabled toggles, we should > probably still extend the documentation to cover "all THP sizes", like > we did elsewhere. > > huge=never: no THPs of any size > huge=always: THPs of any size (fault/write/etc) > huge=fadvise: like "always" but only with fadvise/madvise > huge=within_size: like "fadvise" but respect i_size Thinking some more about that over the weekend, this is likely the way to go, paired with conditionally changing the default to always/within_size. I suggest a kconfig option for that. That should probably do as a first shot; I assume people will want more control over which size to use, especially during page faults, but that can likely be added later. -- Cheers, David / dhildenb