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 48E3328DB62 for ; Wed, 18 Jun 2025 16:14:28 +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=1750263270; cv=none; b=engQIogw9TJGdKt3R5o7jMSJ8NL9a7sronPv4iXyy+Omeal9JHiUF+nmNBSS9vs0hIRbnF6O6cxYCu/hyPCDC1GpeAYDQ4dl7pszdxoNG6NHM0H3V41bTCp5IFf0DJFTYxQEDNxcFiw0bHBH6itSKpLH+/HUU33tWSTfM6iJZ3Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750263270; c=relaxed/simple; bh=SqqhJ8mOIg55dmbqfeFWD5nnZuIaSJAzk6LWwq97lSI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZoV8QR39KCuJ2WU3Yvok1/O/MIzMm+Lhbb6ro3zbxXuCkkvi0DHGyMrR0coUBAUoRrNQZjLl4sh1F9XBm5kAjoG+CCs+7XEsVWVl4Hr7DN4IxUN3DUnGPnDDd7KM9UK1IjMeDoP35KhURxGS5HQ96r3fZGnKqBsU2PfP8POEeOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=XXL2Zy4A; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="XXL2Zy4A" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750263267; 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=qv6rWz3G7zQ3HwLveL9JzkEtus+WQoTHanBk5L+liRk=; b=XXL2Zy4AHVH4qFDXFHhKEMJV3NEDMog8o1H81HPE939lL/7AT5iDz9gmXBOcWo7zkmFKQI L+LXYgUF/2mS9Rau1IgnoYtIhtWClhgCQkOKDxsflDbzBMJYDM+treyEWdmCwlVpAj778C W6koVWqV42XU51PWTBYH0NK6eyRqkjo= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-452-UUJ4GFUQOuGVTp0nxH150A-1; Wed, 18 Jun 2025 12:14:26 -0400 X-MC-Unique: UUJ4GFUQOuGVTp0nxH150A-1 X-Mimecast-MFC-AGG-ID: UUJ4GFUQOuGVTp0nxH150A_1750263265 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-450d6768d4dso46585275e9.2 for ; Wed, 18 Jun 2025 09:14:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750263265; x=1750868065; 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=qv6rWz3G7zQ3HwLveL9JzkEtus+WQoTHanBk5L+liRk=; b=ssOfXlovhtQESRtfgaF0jhQDPZZFpB7PJFDRRauQFHfLX0SG8pjpvJhCZFnG6zSj/E z+aT81WniniC5WxdR+U1JgPydYuolyHXafmiYHaP0BUeFJWNpL99gsuscgMEu/Htea39 VrLl+7etose/q6RBbPz0G6EHW/m4pc9CuleYxtJJiZtMKLRlnS9lQqgrv05CMB5dtB3s 9Mt4A2SUY+uKP/AcSs8eScUDjFolfSnF0UtnYmPaM/5/wyXztK+YokXqLuP0K+87i/GZ 9bDGfcl4eCIGZfqih9uJReGjGl3/E7Qi/mKhlD3g64vuNJE552XoIPAae2uiIDZq2eAi So4w== X-Forwarded-Encrypted: i=1; AJvYcCVVlmCcIlqGe2e1gpzgzuLhTRXpglH/8LFsygnLCx+Edbzkd0ObBKKiYWEB8ZNDqAw/fxwAEU4WC1T3LWg=@vger.kernel.org X-Gm-Message-State: AOJu0YyeM2CEtdJRB90YPw5kyrWp9IC+trruDNYu+f28P1fe9vcjgx6q KXF35unvfanQsx0UncZOWJg5EC3oOOJQNvJiM0J5PjY1Mu6Qvmr7Xdd3JcSFEtUVoeCSTaFFVBP T8jIDMs5ifMuf8AVE7VCDR6yFigIO0MEv04eWX1qYO+wbOukEOM2UkOjR0rJB0PB5lQ== X-Gm-Gg: ASbGncvBEufDaPsEzDXKEMTLB2D3KPHk31K4xtS/RC2qxs05uYfknpEO1dIRhrfT0Gx qADwL82GLAULJtWX5ZHEeCmCp3PjAY6V2ZVbeGSTpdvXbyxIRZoCU2mJYom0X6wxdry8Z/G4YWp pit/Sxg/ipZ6Sf+9zaZXkfNINttlD636XJCGykbcDo5hKESjwq4dWpkg75QQrPcD+ODw2I36RHj IFBsImjnmi2wu5uK0hjds1ht+N0x3e5FuLvFQyzsupRua7dBVfvsm6erlIvw3RowJ91dWL2FE3F evw6PlHv9JkjKWYr63nXaso/ALu2gx8BmnsbD+mChyx2UiXieiBd13fXFg2wUZumHYSUImU9Vrj HOlEdgh+7AtN6a/gv07QIyZmTmYAkKtIYizB8YrLwn6x+KDM= X-Received: by 2002:a05:600c:a089:b0:441:d4e8:76cd with SMTP id 5b1f17b1804b1-4533cb55c28mr171957925e9.29.1750263264608; Wed, 18 Jun 2025 09:14:24 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH9DGEuzgpP2c+6KXNCStjPN6PpIwlpQzQ+R7yaqZtF8tW81pjSe7ZCl5P8XepH5ib4ANXh/A== X-Received: by 2002:a05:600c:a089:b0:441:d4e8:76cd with SMTP id 5b1f17b1804b1-4533cb55c28mr171957635e9.29.1750263264182; Wed, 18 Jun 2025 09:14:24 -0700 (PDT) Received: from ?IPV6:2003:d8:2f2d:2400:4052:3b5:fff9:4ed0? (p200300d82f2d2400405203b5fff94ed0.dip0.t-ipconnect.de. [2003:d8:2f2d:2400:4052:3b5:fff9:4ed0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4535e97abf6sm1813025e9.6.2025.06.18.09.14.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Jun 2025 09:14:23 -0700 (PDT) Message-ID: <738669ec-a9e5-4ba1-85a7-605cb4132d05@redhat.com> Date: Wed, 18 Jun 2025 18:14:22 +0200 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] khugepaged: Optimize __collapse_huge_page_copy_succeeded() for large folios by PTE batching To: Dev Jain , akpm@linux-foundation.org Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250618102607.10551-1-dev.jain@arm.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: <20250618102607.10551-1-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18.06.25 12:26, Dev Jain wrote: > Use PTE batching to optimize __collapse_huge_page_copy_succeeded(). > > On arm64, suppose khugepaged is scanning a pte-mapped 2MB THP for collapse. > Then, calling ptep_clear() for every pte will cause a TLB flush for every > contpte block. Instead, clear_full_ptes() does a > contpte_try_unfold_partial() which will flush the TLB only for the (if any) > starting and ending contpte block, if they partially overlap with the range > khugepaged is looking at. > > For all arches, there should be a benefit due to batching atomic operations > on mapcounts due to folio_remove_rmap_ptes(). > > No issues were observed with mm-selftests. > > Signed-off-by: Dev Jain > --- > mm/khugepaged.c | 31 +++++++++++++++++++++++-------- > 1 file changed, 23 insertions(+), 8 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index d45d08b521f6..649ccb2670f8 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -700,12 +700,14 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte, > spinlock_t *ptl, > struct list_head *compound_pagelist) > { > + unsigned long end = address + HPAGE_PMD_SIZE; > struct folio *src, *tmp; > - pte_t *_pte; > + pte_t *_pte = pte; > pte_t pteval; > + int nr_ptes; > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; > - _pte++, address += PAGE_SIZE) { > + do { > + nr_ptes = 1; > pteval = ptep_get(_pte); > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); > @@ -719,23 +721,36 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte, > ksm_might_unmap_zero_page(vma->vm_mm, pteval); > } > } else { > + const fpb_t flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; > + int max_nr_ptes; > + bool is_large; folio_test_large() should be cheap, no need for the temporary variable (the compiler will likely optimize this either way). > + > struct page *src_page = pte_page(pteval); > > src = page_folio(src_page); > - if (!folio_test_large(src)) > + is_large = folio_test_large(src); > + if (!is_large) > release_pte_folio(src); > + > + max_nr_ptes = (end - address) >> PAGE_SHIFT; > + if (is_large && max_nr_ptes != 1) > + nr_ptes = folio_pte_batch(src, address, _pte, > + pteval, max_nr_ptes, > + flags, NULL, NULL, NULL); Starting to wonder if we want a simplified, non-inlined version of folio_pte_batch() in mm/util.c (e.g., without the 3 NULL parameters), renaming existing folio_pte_batch to __folio_pte_batch() and only using it where required (performance like in fork/zap, or because the other parameters are relevant). Let me see if I find time for a quick patch later. Have to look at what other similar code needs. > + > /* > * ptl mostly unnecessary, but preempt has to > * be disabled to update the per-cpu stats > * inside folio_remove_rmap_pte(). > */ > spin_lock(ptl); Existing code: The PTL locking should just be moved outside of the loop. > - ptep_clear(vma->vm_mm, address, _pte); > - folio_remove_rmap_pte(src, src_page, vma); > + clear_full_ptes(vma->vm_mm, address, _pte, nr_ptes, false); Starting to wonder if we want a shortcut #define clear_ptes(__mm, __addr, __pte, __nr_ptes) \ clear_full_ptes(__mm, __addr, __pte, __nr_ptes, false) > + folio_remove_rmap_ptes(src, src_page, nr_ptes, vma); > spin_unlock(ptl); > - free_folio_and_swap_cache(src); > + free_swap_cache(src); > + folio_put_refs(src, nr_ptes); > } > - } > + } while (_pte += nr_ptes, address += nr_ptes * PAGE_SIZE, address != end); > > list_for_each_entry_safe(src, tmp, compound_pagelist, lru) { > list_del(&src->lru); I think this should just work. -- Cheers, David / dhildenb