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 6DCFBC021AA for ; Tue, 18 Feb 2025 20:57:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C912228019F; Tue, 18 Feb 2025 15:57:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C410E28019B; Tue, 18 Feb 2025 15:57:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A94D328019F; Tue, 18 Feb 2025 15:57:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 8B3ED28019B for ; Tue, 18 Feb 2025 15:57:17 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 2853C4B4CB for ; Tue, 18 Feb 2025 20:57:17 +0000 (UTC) X-FDA: 83134275714.21.4EBF230 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf16.hostedemail.com (Postfix) with ESMTP id B449018000E for ; Tue, 18 Feb 2025 20:57:14 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=cpNjySLk; spf=pass (imf16.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1739912234; 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=6FsbwLcxUhHZW9FHTie3Ead3JpCjVkROaSdeAT2Lgyo=; b=Skstt52CCVY+xh7A1xC4dteJvv1cMpuBe/pWeCUBGYviUoekcm86QVWyPh1zkLTcVZFz69 /MD0PneEO6k3mLkjfomYWLdPFMiVRGegNvT2yFP0sDJbx8tfi4ZfooUUWu7GJINIjRV4TZ Z0hSugLoB4ivL28sytyuaSoKVX3OEyM= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=cpNjySLk; spf=pass (imf16.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1739912234; a=rsa-sha256; cv=none; b=k9ZuHidm8NNo/CvUyYntxCQ/+1z8wCksLYe6TpXZdiKQ3BgQG2iR0XnhUmE78UUn6dqoW1 NCwmW8Hs/zo1Ld9l4R4QP8qdGhmEEUi7xC0GHIv8ci4Sl7jBemo4dCqEewy1fvDW0jPhXP qkLokP05H2D32YEwEkMFcyEvyrTW0NM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739912234; 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=6FsbwLcxUhHZW9FHTie3Ead3JpCjVkROaSdeAT2Lgyo=; b=cpNjySLk2dvgJFD+HaxgcG38dY5ZlGg1qdXdvrrejvSBj1GPuDN//jZ9CWpMK6pYuy4dwT rAtScikRrl8c9Mo4Qj8otWsPqh/DJ/xf98v83xkzuDo6G9zC0yCjuKr3gcPUM2kkD6jbbi 6ewxF5SKkDiteDIn5BWgK6PBa+TBFis= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-589-fnOKmYS_NZahTzuVMfFIqg-1; Tue, 18 Feb 2025 15:57:10 -0500 X-MC-Unique: fnOKmYS_NZahTzuVMfFIqg-1 X-Mimecast-MFC-AGG-ID: fnOKmYS_NZahTzuVMfFIqg_1739912230 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-38f4e47d0b2so920523f8f.2 for ; Tue, 18 Feb 2025 12:57:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739912229; x=1740517029; 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=6FsbwLcxUhHZW9FHTie3Ead3JpCjVkROaSdeAT2Lgyo=; b=DtG+uxp8PuBWIGSeezzjqyHzUoDCR6zouQY5GhbasZ4jlDsf195MiiijJbM1Eigyw3 OmMjobEXcq4S5NrQIHIlxCoNUbZ41vAPsoBTJ0Sh4qQRmtq5Z5xWu8Thcif1n8nUZgAz NgMbP0vSzSeePbWqRv1Jl4tr6nCP3yifyuwvfaNw3vq/M3vPjTxUPo7A7PzjwTR1TkZZ UrqS/jkfXK8xET4u/cQ1Nj5l3PbwMuZr5zwSWB2Q1rcEIhQL01AjQbEF4wKYA52XIrVu DUrIptVoGpwjJo9BRSbJnLv3YZGt5JJ6eWbotdk2tP7rXilcSrxzLbWqtWjMbLSqWEDr rDEQ== X-Forwarded-Encrypted: i=1; AJvYcCXEO917MqVe9wEeYUGT5c7i+WaGdjI0DCNhxs74GMmifW0twKb/gtcNtFC68zu7yOT4KUfzoKv1CA==@kvack.org X-Gm-Message-State: AOJu0YyNpvNr4jwFJfFLiZKq6dKSVKWLmge1+K0tkCBVcG+z8qk7C67+ EuMRhm6rzVzeUT2Ff69GNbyFQg23l5AaBbU1l0gWP3ZfRRGoTQBWiWWJwD1f9kRZWFe2t7FvDIk kRKd9tgAcVqTRXGaRiBPw3Ko7FEA5DKaX/whgIFA+0sFd/lCN X-Gm-Gg: ASbGncs1O+aTgnbBGJ5g7NrHwNi2FuO+VSHmqeE+L96e+15vWsWPP6E2QYhy+FopN6u CuSlUzTHILWWbRa9gfChAJEZ6zPrS20DK0JheROtayGBM4udgaM2zrxQhHBucJgy2sYYPgkI+7J yIgSmgM179a3UMJkZ+wXk/5W1kAFlfIqCZDET70+It6r6nJO5A8Nrw70FmF1lAOfS/mBo0Jk/AI eqguulMpNFN53Fa+TFHGAL6PemBT++fMGtgawZgKJCCPq6sV+yiFBdWQSYpShDbSkCGzQixYyyd E92cj/UJT9kfVQSKd5pB7a5z/hW+SlBzwMRzksQjUUmJ0ttBZElLqmziOzdM8xpPeOsrtZWELhl SKHe9euKGfFgufBea1KpZaYE6CLp2LIE3 X-Received: by 2002:a05:6000:1faf:b0:38f:3392:9fd8 with SMTP id ffacd0b85a97d-38f5878dea4mr808589f8f.18.1739912229605; Tue, 18 Feb 2025 12:57:09 -0800 (PST) X-Google-Smtp-Source: AGHT+IEhJl5VYJN1ZER6U6SOjF2yYBkVq3hxhtLzuzokjKHCH1grxuxyGuoLNfn8/aO4cMRuRSnstQ== X-Received: by 2002:a05:6000:1faf:b0:38f:3392:9fd8 with SMTP id ffacd0b85a97d-38f5878dea4mr808574f8f.18.1739912229238; Tue, 18 Feb 2025 12:57:09 -0800 (PST) Received: from ?IPV6:2003:cb:c70d:fb00:d3ed:5f44:1b2d:12af? (p200300cbc70dfb00d3ed5f441b2d12af.dip0.t-ipconnect.de. [2003:cb:c70d:fb00:d3ed:5f44:1b2d:12af]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43987d1865asm62509405e9.3.2025.02.18.12.57.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 12:57:08 -0800 (PST) Message-ID: Date: Tue, 18 Feb 2025 21:57:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: CXL Boot to Bash - Section 3: Memory (block) Hotplug To: Gregory Price Cc: Yang Shi , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org References: <1b4c6442-a2b0-4290-8b89-c7b82a66d358@redhat.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-MFC-PROC-ID: rrJ5QjLEddUabtm8JdtIXuHT6pSCysZiVHGZqav_CXw_1739912230 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: rspam08 X-Rspamd-Queue-Id: B449018000E X-Stat-Signature: d4wj36er8r5r597uynagr3jamseaqrwn X-HE-Tag: 1739912234-243210 X-HE-Meta: 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 G0/twpip YVoRVCqNFjuDknjl39y/Q7djn+VfGKehGATdudPRBNqyMJcD5o7bB0m8pUrN0aSaBI6LqNd4H2gk7xFeqUqou3CUw+SnO+udgfRC4M1Da/vn2aN3GGdUpWb1ikLG8/0gDZ942/ew4pg2XFBDfq2+lFVAkpEyiCt28oDy2tEERQKenADm6G0ppFD6DEJIZuIOdGlZOfT0K94Woig8IOp9/ds8gtoKpbH5iTycs+IyAPpbSEIShAQe4vHOY+eZZqvliQqJntSN55bPNUF2k+e0FVeQl6zsa8FHSPRcHM76/+kY9Bd8tb+kYFhjG1zVlOd4cjypmGZrilZ+D7lPWqFXHTSGyg7JwgPukc8Q4yhOXEF+VajmyiacCRlyIXR+8OZkd5jAXszyzIzVdfhF5AVmn8shEFaQJ1GpP1MgRzK2+unx4F9nEALllomM1lRjaT55+DmPtMF46oE/gd19ZwX6kUoj4lNS+2yGUUd/yBq8fhyFrZnc= 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 18.02.25 21:25, Gregory Price wrote: > On Tue, Feb 18, 2025 at 08:25:59PM +0100, David Hildenbrand wrote: >> On 18.02.25 19:04, Gregory Price wrote: >> >> Hm? >> >> If you enable memmap_on_memory, we will place the memmap on that carved-out >> region, independent of ZONE_NORMAL/ZONE_MOVABLE etc. It's the "altmap". >> >> Reason that we can place the memmap on a ZONE_MOVABLE is because, although >> it is "unmovable", we told memory offlining code that it doesn't have to >> care about offlining that memmap carveout, there is no migration to be done. >> Just offline the block (memmap gets stale) and remove that block (memmap >> gets removed). >> >> If there is a reason where we carve out the memmap and *not* use it, that >> case must be fixed. >> > > Hm, I managed to trace down the wrong path on this particular code. > > I will go back and redo my tests to sanity check, but here's what I > would expect to see: > > 1) if memmap_on_memory is off, and hotplug capacity (node1) is > zone_movable - then zone_normal (node0) should have N pages > accounted in nr_memmap_pages Right, we'll allocate the memmap from the buddy, which ends up allocating from ZONE_NORMAL on that node. > > 1a) when dropping these memory blocks, I should see node0 memory > use drop by 4GB - since this is just GFP_KERNEL pages. I assume you mean "when hotunplugging them". Yes, we should be freeing the memmap back to the buddy. > > 2) if memmap_on_memory is on, and hotplug capacity (node1) is > zone_movable - then each memory block (256MB) should appear > as 252MB (-4MB of 64-byte page structs). For 256GB (my system) > I should see a total of 252GB of onlined memory (-4GB of page struct) In memory_block_online(), we have: /* * Account once onlining succeeded. If the zone was unpopulated, it is * now already properly populated. */ if (nr_vmemmap_pages) adjust_present_page_count(pfn_to_page(start_pfn), mem->group, nr_vmemmap_pages); So we'd add the vmemmap pages to * zone->present_pages * zone->zone_pgdat->node_present_pages (mhp_init_memmap_on_memory() moved the vmemmap pages to ZONE_MOVABLE) However, we don't add them to * zone->managed_pages * totalram pages /proc/zoneinfo would show them as present but not managed. /proc/meminfo would not include them in MemTotal We could adjust the latter two, if there is a problem. (just needs some adjust_managed_page_count() calls) So yes, staring at MemTotal, you should see an increase by 252 MiB right now. > > 2a) when dropping these memory blocks, I should see node0 memory use > stay the same - since it was vmemmap usage. Yes. > > I will double check that this isn't working as expected, and i'll double > check for a build option as well. > > stupid question - it sorta seems like you'd want this as the default > setting for driver-managed hotplug memory blocks, but I suppose for > very small blocks there's problems (as described in the docs). The issue is that it is per-memblock. So you'll never have 1 GiB ranges of consecutive usable memory (e.g., 1 GiB hugetlb page). > > :thinking: - is it silly to suggest maybe a per-driver memmap_on_memory > setting rather than just a global setting? For CXL capacity, this seems > like a no-brainer since blocks can't be smaller than 256MB (per spec). I thought we had that? See MHP_MEMMAP_ON_MEMORY set by dax/kmem. IIRC, the global toggle must be enabled for the driver option to be considered. -- Cheers, David / dhildenb