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 329D8C47422 for ; Mon, 29 Jan 2024 10:27:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8B1D76B009C; Mon, 29 Jan 2024 05:27:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8611A6B009D; Mon, 29 Jan 2024 05:27:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6DB1E6B009E; Mon, 29 Jan 2024 05:27:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 563016B009C for ; Mon, 29 Jan 2024 05:27:57 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id D699C4096A for ; Mon, 29 Jan 2024 10:27:56 +0000 (UTC) X-FDA: 81731972952.16.987E8F3 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf07.hostedemail.com (Postfix) with ESMTP id 8979340017 for ; Mon, 29 Jan 2024 10:27:54 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VKEYAxps; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf07.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706524074; a=rsa-sha256; cv=none; b=RUbB6990i/qEIuUsc/dJ3xxsVIf+lHf6leILRYhGdFQ976MKSffthxQ87FRf6FKr2tIGNT FkfX2iG5/JLqTa7rkpUG/yljGcTCPUgq42Esq7etamXO1Wl4G/dgrp9pcpIk1xmJmn0PEZ n+dDvSFNeWzeYZwP8V1nvAcx+Lp5dIk= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VKEYAxps; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf07.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706524074; 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=Gtt2+W0a7+pXVqkgz06pfnEh9MgiEut6I2Y5IUeSq8s=; b=5mS6gO62TW0V/VnJLs/0eoA0EkJoATde/As6aG46ymZGUfm4Wm5UIJZQa6uK3J25E7psEW am+K2c5ZivG3/FYwFs/eU1vVPhHKY+jPZ/sLEdGb3LcQat1QqSCPuDKw49+yL3FRhXjqh1 6TmU/ZAEC4u21JRFdAIh1E/yHaoqFg4= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706524073; 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=Gtt2+W0a7+pXVqkgz06pfnEh9MgiEut6I2Y5IUeSq8s=; b=VKEYAxpsWWQ96KENYKf5qlyYV5NMk3l9mJO9zI5M4h8XJ6yPNTR+a1nD7YbWKwk03qRRMK fiS5V6d7GscLHvI30UpHrRE0GDYzg+cBdrdJXjynkYaa6MTWwAu4LjFNNOJ3Bat8eFwxFX SS9/VnIJ7LS7SClzFcZwGuoSfXoiZj8= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-540-RIVLBQHkOnmwtORmFHAahg-1; Mon, 29 Jan 2024 05:27:51 -0500 X-MC-Unique: RIVLBQHkOnmwtORmFHAahg-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-40ef6b8d0f6so4700845e9.2 for ; Mon, 29 Jan 2024 02:27:51 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706524070; x=1707128870; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Gtt2+W0a7+pXVqkgz06pfnEh9MgiEut6I2Y5IUeSq8s=; b=ktRGFWZyEAOHTJ18vBQIEwnXAaU8EDquvAPeUHr7EODvjWFkcn7p76BksDh5GSzjT4 FgIFGH+pNkrVOVi7TQYNW1NqcTlMKaPMZKOb7JM9ZndIK462nWtuOX9j8S+iP4PisCkB 1bNZK0QUexVrU67E9876V3os2eLpnHbNi7wqbWVPQqX6zmH2ZvtxERY42IHYq7vDWO6I 0Hvmp7AuzGsMPxFvy9zBYfuQ2j2rwk/juF8TmM1XanXfwISbZySUyZAZ8bcjR+sS8d95 ghm87MQ2m4ooFlOByk3pFc6mbUQTQbsbmEZQ4s86VrSM71NoZSKZ03j2uD8jxo1WOp7X lNPg== X-Gm-Message-State: AOJu0Yx+DNxf1cQZIe+C6e92rlPMecGQ3BsXyDuzIkpLOJ2Sa6iJoQ46 BFOxBztLGB+IAzyqx5A/JCzgV6fceKMJVPasPeLiHY8lWl/e0Dei5759Ce2UtsOfEdVs5EdVVVG AEQobYtl2de+ZmddCVxzzS5X8O8KqL8xk64qfSr7fA9r7P/oV X-Received: by 2002:a05:600c:4e88:b0:40e:c6d7:4207 with SMTP id f8-20020a05600c4e8800b0040ec6d74207mr4489604wmq.9.1706524070759; Mon, 29 Jan 2024 02:27:50 -0800 (PST) X-Google-Smtp-Source: AGHT+IG8cc4xFddicaS2g1OXR2SgEPAfHUX3dg8sijEj51Z/ofwIM8b41CYK0p+YwIBmcUhtFv4+8A== X-Received: by 2002:a05:600c:4e88:b0:40e:c6d7:4207 with SMTP id f8-20020a05600c4e8800b0040ec6d74207mr4489577wmq.9.1706524070375; Mon, 29 Jan 2024 02:27:50 -0800 (PST) Received: from ?IPV6:2003:cb:c721:aa00:3221:f685:1200:6d03? (p200300cbc721aa003221f68512006d03.dip0.t-ipconnect.de. [2003:cb:c721:aa00:3221:f685:1200:6d03]) by smtp.gmail.com with ESMTPSA id u16-20020a05600c19d000b0040e4733aecbsm9605409wmq.15.2024.01.29.02.27.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jan 2024 02:27:50 -0800 (PST) Message-ID: Date: Mon, 29 Jan 2024 11:27:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] Memory tiering kernel alignment To: Matthew Wilcox , David Rientjes Cc: John Hubbard , Zi Yan , Bharata B Rao , Dave Jiang , "Aneesh Kumar K.V" , "Huang, Ying" , Alistair Popple , Christoph Lameter , Andrew Morton , Linus Torvalds , Dave Hansen , Mel Gorman , Jon Grimm , Gregory Price , Brian Morris , Wei Xu , Johannes Weiner , linux-mm@kvack.org References: <75f21150-1e12-4f4b-e578-e170e4fea18b@google.com> <2b29dd3d-bb2c-6a8c-94d2-d5c2e035516a@google.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: 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: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8979340017 X-Stat-Signature: bsmfnuz1jc3nni5eb6g45odsc8i9acyy X-HE-Tag: 1706524074-574926 X-HE-Meta: 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 Hrwp0JZJ 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 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 25.01.24 21:19, Matthew Wilcox wrote: > On Thu, Jan 25, 2024 at 12:04:37PM -0800, David Rientjes wrote: >> On Thu, 25 Jan 2024, Matthew Wilcox wrote: >>> On Thu, Jan 25, 2024 at 10:26:19AM -0800, David Rientjes wrote: >>>> There is a lot of excitement around upcoming CXL type 3 memory expansion >>>> devices and their cost savings potential. As the industry starts to >>>> adopt this technology, one of the key components in strategic planning is >>>> how the upstream Linux kernel will support various tiered configurations >>>> to meet various user needs. I think it goes without saying that this is >>>> quite interesting to cloud providers as well as other hyperscalers :) >>> >>> I'm not excited. I'm disappointed that people are falling for this scam. >>> CXL is the ATM of this decade. The protocol is not fit for the purpose >>> of accessing remote memory, adding 10ns just for an encode/decode cycle. >>> Hands up everybody who's excited about memory latency increasing by 17%. >> >> Right, I don't think that anybody is claiming that we can leverage locally >> attached CXL memory as through it was DRAM on the same or remote socket >> and that there won't be a noticable impact to application performance >> while the memory is still across the device. >> >> It does offer several cost savings benefits for offloading of cold memory, >> though, if locally attached and I think the support for that use case is >> inevitable -- in fact, Linux has some sophisticated support for the >> locally attached use case already. >> >>> Then there are the lies from the vendors who want you to buy switches. >>> Not one of them are willing to guarantee you the worst case latency >>> through their switches. >> >> I should have prefaced this thread by saying "locally attached CXL memory >> expansion", because that's the primary focus of many of the folks on this >> email thread :) > > That's a huge relief. I was not looking forward to the patches to add > support for pooling (etc). The issue is that CXL standard is at this point extremely over-engineered with obscure use cases, and features that feel completely detached from reality -- especially, what a commodity OS can support and would be willing to support. Thanks for expressing what I've been thinking all of the time. CXL is IMHO great for cheap (slow/cold) memory, GPGPUs etc, and I'm hoping that will be the primary focus for the near future -- not all of that dynamic capacity, memory pooling etc crap (sorry). -- Cheers, David / dhildenb