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 A6E9846B8 for ; Mon, 9 Dec 2024 21:35:31 +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=1733780133; cv=none; b=HragpqekVnwey9IsLj6/aIxEfOFWW6+b41uc4nvVtQ8vukWSv8KKYJ78hDJy+F6hF8aJHFuw5Xyj9m0vW3lnus03uDslkzVLN7T4SOVYJMg5IL/fRHrq+qhQRINPENycAyX0SGpfPhM07slbTqPRTOaewVHYdvg21eSbaN/qCnE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733780133; c=relaxed/simple; bh=Ur8mB59paoe0fWuu808yYLLVrha1nH4CxuFXuQwAGR0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dFnFNLYKx/vgFfL7Dts7hnG8CoEGLldrBBOEdvmLaGO5f7C7fOcbI24/AWhy3Goj1H9wU5bg5xj/+nrhwcGNoSiqxm+xy3X8ZEBwvMj4VFjIxlhE/J4LKh1Zu4QkWZdeS/9EsJKPhlbkwl3zdjMtTRriXaacvcdL1rAXCLHce6U= 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=UpFjKrvC; 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="UpFjKrvC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1733780130; 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=70n3xdSaZgXZO2ROhuJrTZaqwaJdkTElowkjJvLcak0=; b=UpFjKrvCc/C9dUWLMqlm74Q3I65qLq26AoMu4q5teeTulMEEbia28Q0Q9NjnM8aYh6eZHn Vc+oMfCp06/0CZTbwPeBRMsOy+8PMi0mRRIPu2+IW1oWm9raJQG3ODO8LNRsSW+6vLcDmb SJdsmBkU5Fd6EHCSU9cgsbCHt0wttOg= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-516-5jxv8TjjMoyJtDZn8xAecQ-1; Mon, 09 Dec 2024 16:35:29 -0500 X-MC-Unique: 5jxv8TjjMoyJtDZn8xAecQ-1 X-Mimecast-MFC-AGG-ID: 5jxv8TjjMoyJtDZn8xAecQ Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-434f3398326so8125225e9.0 for ; Mon, 09 Dec 2024 13:35:29 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733780128; x=1734384928; 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=70n3xdSaZgXZO2ROhuJrTZaqwaJdkTElowkjJvLcak0=; b=f3FyhnEC8xMOKuHcn1VnKM74ocBxbKAD5c4Ug6wDJ7c4GhXCwr2sSt9Ex6X8P6ECSl wbNB5lA5PhQNKQPTSjpV8iqye1yifQn5wPHPsuhqMMVOb5tOnk+QLwW4ptOWAaETLh+T TGdeE08A1WdN0jrrgHecov2+/rj6Gc3dPFHVsoyy+2g6l8vX9AubSrJeD+B6FTu0Htsq +QSX0NQQjptN9siVMG5he//0oyjblTyNah6OCO6Kkm0BHoVXsrsjo6nqAKtBqNCNM9ko blv3zt6VMXYo+iV5Mbr+h0gzpp9snMJRyaLJShragOQy7aqpX+1QJmgG2S56RcrHkwtV jcLA== X-Gm-Message-State: AOJu0YxZIGTnkubDOwD/5t8hiKYgk2+SguxdpWfMtLZvtA+u7z6WwOS7 7I5AB4dPa53P/ezh7qEFEz88PlXqgFY6MRQcWphjwmhQQvKv18jSXA/uEj0a402ZMRN889+0QJa twYvvdzZQnk1/x/MvjAiouvu4eEEt7wqZT/5y372CHHm33ZjI68rK2aBQiVO3l4xlMiI2iw== X-Gm-Gg: ASbGnctT//5V+54UqHx6c2OrmwM2cL8mcKaW+PsCiZRkBYfd+BVbMzgPlY0Vbt/ZV9n ulG9uf7EMPGqYoE2NGYjR+S+JcxXz/OFHjbNdbzfpCjFPBqMM0B96ovVZwrYeDm9QEyKUGz9nAC lcEezSTbg7StkfKVJ8UE2VfH20Dtf7bdogRvnbKiPSt4HTPL+WQcj+ZGpM3tl2vqAbZZXWOJKIT SMvJfAg8ciXmLdo+HshcrpJamHr7liy8GQMG1sdqNHKVYXf8Kvdjk9+dekI8gxj1Dk2CeGfxGgg xDMZarpLCdHH91Z9H4qiSbZR5VcJ8ek+xVuPxntQOkDGGNxE796cgKH1wL0EUvQ5whPOAnVVz+r F9Jqg3A== X-Received: by 2002:a05:600c:1791:b0:431:15f1:421d with SMTP id 5b1f17b1804b1-435021e916emr6443895e9.16.1733780128154; Mon, 09 Dec 2024 13:35:28 -0800 (PST) X-Google-Smtp-Source: AGHT+IG40vlopO3K0D70apQhM15wsvzbvmNktiJfG0OC439H7arNAniPqnPN6AKEeuu1AiCMWIZTDw== X-Received: by 2002:a05:600c:1791:b0:431:15f1:421d with SMTP id 5b1f17b1804b1-435021e916emr6443765e9.16.1733780127803; Mon, 09 Dec 2024 13:35:27 -0800 (PST) Received: from ?IPV6:2003:cb:c71b:2c00:7bfb:29fe:9e6f:2e65? (p200300cbc71b2c007bfb29fe9e6f2e65.dip0.t-ipconnect.de. [2003:cb:c71b:2c00:7bfb:29fe:9e6f:2e65]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4350159f6a4sm12209525e9.21.2024.12.09.13.35.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Dec 2024 13:35:26 -0800 (PST) Message-ID: Date: Mon, 9 Dec 2024 22:35:25 +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 v1 1/2] mm/page_alloc: conditionally split > pageblock_order pages in free_one_page() and move_freepages_block_isolate() To: Zi Yan , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, Johannes Weiner , linux-mm@kvack.org, Andrew Morton , Yu Zhao References: <20241206095951.98007-1-david@redhat.com> <20241206095951.98007-2-david@redhat.com> <37B7A92E-B58F-442D-8501-B07A507F0451@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: <37B7A92E-B58F-442D-8501-B07A507F0451@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 09.12.24 20:23, Zi Yan wrote: > On 9 Dec 2024, at 14:01, Vlastimil Babka wrote: > >> On 12/6/24 10:59, David Hildenbrand wrote: >>> Let's special-case for the common scenarios that: >>> >>> (a) We are freeing pages <= pageblock_order >>> (b) We are freeing a page <= MAX_PAGE_ORDER and all pageblocks match >>> (especially, no mixture of isolated and non-isolated pageblocks) >> >> Well in many of those cases we could also just adjust the pageblocks... But >> perhaps they indeed shouldn't differ in the first place, unless there's an >> isolation attempt. >> >>> When we encounter a > MAX_PAGE_ORDER page, it can only come from >>> alloc_contig_range(), and we can process MAX_PAGE_ORDER chunks. >>> >>> When we encounter a >pageblock_order <= MAX_PAGE_ORDER page, >>> check whether all pageblocks match, and if so (common case), don't >>> split them up just for the buddy to merge them back. >>> >>> This makes sure that when we free MAX_PAGE_ORDER chunks to the buddy, >>> for example during system startups, memory onlining, or when isolating >>> consecutive pageblocks via alloc_contig_range()/memory offlining, that >>> we don't unnecessarily split up what we'll immediately merge again, >>> because the migratetypes match. >>> >>> Rename split_large_buddy() to __free_one_page_maybe_split(), to make it >>> clearer what's happening, and handle in it only natural buddy orders, >>> not the alloc_contig_range(__GFP_COMP) special case: handle that in >>> free_one_page() only. >>> >>> Signed-off-by: David Hildenbrand >> >> Acked-by: Vlastimil Babka > >> Hm but noticed something: >> >>> +static void __free_one_page_maybe_split(struct zone *zone, struct page *page, >>> + unsigned long pfn, int order, fpi_t fpi_flags) >>> +{ >>> + const unsigned long end_pfn = pfn + (1 << order); >>> + int mt = get_pfnblock_migratetype(page, pfn); >>> + >>> + VM_WARN_ON_ONCE(order > MAX_PAGE_ORDER); >>> VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order)); >>> /* Caller removed page from freelist, buddy info cleared! */ >>> VM_WARN_ON_ONCE(PageBuddy(page)); >>> >>> - if (order > pageblock_order) >>> - order = pageblock_order; >>> - >>> - while (pfn != end) { >>> - int mt = get_pfnblock_migratetype(page, pfn); >>> + /* >>> + * With CONFIG_MEMORY_ISOLATION, we might be freeing MAX_ORDER_NR_PAGES >>> + * pages that cover pageblocks with different migratetypes; for example >>> + * only some migratetypes might be MIGRATE_ISOLATE. In that (unlikely) >>> + * case, fallback to freeing individual pageblocks so they get put >>> + * onto the right lists. >>> + */ >>> + if (!IS_ENABLED(CONFIG_MEMORY_ISOLATION) || >>> + likely(order <= pageblock_order) || >>> + pfnblock_migratetype_equal(pfn + pageblock_nr_pages, end_pfn, mt)) { >>> + __free_one_page(page, pfn, zone, order, mt, fpi_flags); >>> + return; >>> + } >>> >>> - __free_one_page(page, pfn, zone, order, mt, fpi); >>> - pfn += 1 << order; >>> + while (pfn != end_pfn) { >>> + mt = get_pfnblock_migratetype(page, pfn); >>> + __free_one_page(page, pfn, zone, pageblock_order, mt, fpi_flags); >>> + pfn += pageblock_nr_pages; >>> page = pfn_to_page(pfn); >> >> This predates your patch, but seems potentially dangerous to attempt >> pfn_to_page(end_pfn) with SPARSEMEM and no vmemmap and the end_pfn perhaps >> being just outside of the valid range? Should we change that? >> >> But seems this code was initially introduced as part of Johannes' >> migratetype hygiene series. > > It starts as split_free_page() from commit b2c9e2fbba32 ("mm: make > alloc_contig_range work at pageblock granularity”), but harmless since > it is only used to split a buddy page. Then commit fd919a85cd55 ("mm: > page_isolation: prepare for hygienic freelists") refactored it, which > should be fine, since it is still used for the same purpose in page > isolation. Then commit e98337d11bbd ("mm/contig_alloc: support __GFP_COMP") > used it for gigantic hugetlb. > > For SPARSEMEM && !SPARSEMEM_VMEMMAP, PFNs are contiguous, vmemmap might not > be. The code above using pfn in the loop might be fine. And since order > is provided, unless the caller is providing a falsely large order, pfn > should be valid. Or am I missing anything? I think the question is, what happens when we call pfn_to_page() on a PFN that falls into a memory section that is either offline, doesn't have a memmap, or does not exist. With CONFIG_SPARSEMEM, we do a struct mem_section *__sec = __pfn_to_section(__pfn) __section_mem_map_addr(__sec) + __pfn; __pfn_to_section() can return NULL, in which case __section_mem_map_addr() would dereference NULL. I assume it ould happen in corner cases, if we'd exceed NR_SECTION_ROOTS. (IOW, large memory, and we free a page that is at the very end of physical memory). Likely, we should do the pfn_to_page() before the __free_one_page() call. -- Cheers, David / dhildenb