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 B507DC4345F for ; Thu, 11 Apr 2024 15:46:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0FA236B0089; Thu, 11 Apr 2024 11:46:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0A9BA6B008A; Thu, 11 Apr 2024 11:46:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E8BC76B008C; Thu, 11 Apr 2024 11:46:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id CC2E26B0089 for ; Thu, 11 Apr 2024 11:46:54 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 89F3D1A0995 for ; Thu, 11 Apr 2024 15:46:54 +0000 (UTC) X-FDA: 81997679148.16.9B1C3CA Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf21.hostedemail.com (Postfix) with ESMTP id 30C851C001E for ; Thu, 11 Apr 2024 15:46:52 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=V9VZZGTs; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 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=1712850412; 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=UEZGV9VCe3aTsy6N7RQCWu4uCsIfjLyWqxbtHAKGNN4=; b=cKtJFx/Q6Whyktud8POe3OnnIIBnyg36XXMb5XGTOGW3UCmg24IFX4gqklOc06axFkaO0D M+jzrgQDgSWP7pJmSWwi0JKouZmZRNaWImz/GPK8h5Aurz7+ju5C3NYBDUQVlTfFPKP6Y3 u5vwDVapHFDbiBK87TpbTjnXKjxL9jU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712850412; a=rsa-sha256; cv=none; b=B5wn74EGxMrm/Yn6geuHOHlWfItDXbY5jCuFJsxR0J1eIRvR07D+kFLbktM4i4/S+XR0ZC qDbQ5OILN9X/GAopAuIM/WgGdg9cYMZZAD9vsfcgdRubKvTfZvGUcg6Xtl41NA6TImPm8P QSMm9RzIwzBUA7Z51K2SCnc4yBf/uVg= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=V9VZZGTs; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712850411; 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=UEZGV9VCe3aTsy6N7RQCWu4uCsIfjLyWqxbtHAKGNN4=; b=V9VZZGTsT3RCY+6VcemGSonnjbu0pG4kg8j43AdQD/XVCxdD+GUQGyqI7BwaIYidGDlXIW vJdmuv1QLEBWoZ/zpbKUsPHjA5/rd2CiVSjFxHkzHtCEmblo2ZsINhlBGABybWCM7q3C12 a+BauDExWDv8pudYfkU03KPneVqkTOA= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-586-XG75gedCOnqSGnRlcw-tTg-1; Thu, 11 Apr 2024 11:46:48 -0400 X-MC-Unique: XG75gedCOnqSGnRlcw-tTg-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-41641a8895dso88545e9.0 for ; Thu, 11 Apr 2024 08:46:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712850407; x=1713455207; 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=UEZGV9VCe3aTsy6N7RQCWu4uCsIfjLyWqxbtHAKGNN4=; b=lXqSrJkFlje6PKakJt5kvvcfsgQjKjo/iriwa7Nvw6z554ZvqfVlK6jsxwKNroPHZ4 KzgtMXy/bZi+ou64n0yHXSaMsffaVkACoZUOhvY9ABytBRX55gyvGEbF7dxM5zT8gLU7 ZktRhL3SyU4uQIUhkWW3Kj56726S+0cd2asFQ1JMt0YsdIOh2bH5VMhsiEvUbfd0y7um Q8MtevJLILbjTG7YVI4DW18Nv8H7s35Uytx0aTGvgxw93P/zsAF73WVPovDwI60vEz0k i0ZIWGjmhed/Cvso2UcYalPm34GWkVKiMCLw+ETfBPIGkXGo+6OEMXsg5iiUOPiqiy5T QicA== X-Forwarded-Encrypted: i=1; AJvYcCWo7nMzQLfwtrW00SwTRB8PHHNzZG8pnGjo8JTg8KvkpvTEU28WM2qPUg/Od1jaWbXz8d2aTjYrkJMD64en5ec0pHk= X-Gm-Message-State: AOJu0YyI2LsNiduNmh7OWnH4liz5JIs+gV5K8qXhcegAfaFyFCX4S8Ua FrFydou6CI+wN89bby6NUCEnybSETKVw0X/p9P3tURT1vSDS82BmC6TVBIbNztjquMLX4Kvu3Fq izC3CKYIqT1ksu4EDVyuyaILSKejl8nPFoSr77LFxUcSm0zcq X-Received: by 2002:a05:600c:35ce:b0:416:9e38:3bdd with SMTP id r14-20020a05600c35ce00b004169e383bddmr129430wmq.27.1712850407037; Thu, 11 Apr 2024 08:46:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGxor1/9ucJeIy1LK54eldxqmchESlilSiUTk4WniHLuvcgqIR+xz6Rwmt5XvZDncL3E9GVSQ== X-Received: by 2002:a05:600c:35ce:b0:416:9e38:3bdd with SMTP id r14-20020a05600c35ce00b004169e383bddmr129396wmq.27.1712850405736; Thu, 11 Apr 2024 08:46:45 -0700 (PDT) Received: from ?IPV6:2003:cb:c724:4300:430f:1c83:1abc:1d66? (p200300cbc7244300430f1c831abc1d66.dip0.t-ipconnect.de. [2003:cb:c724:4300:430f:1c83:1abc:1d66]) by smtp.gmail.com with ESMTPSA id o4-20020a05600c510400b0041624ddff48sm5919487wms.28.2024.04.11.08.46.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Apr 2024 08:46:45 -0700 (PDT) Message-ID: Date: Thu, 11 Apr 2024 17:46:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/rmap: do not add fully unmapped large folio to deferred split list To: Zi Yan , linux-mm@kvack.org Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , Yang Shi , Ryan Roberts , Barry Song <21cnbao@gmail.com>, linux-kernel@vger.kernel.org References: <20240411153232.169560-1-zi.yan@sent.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: <20240411153232.169560-1-zi.yan@sent.com> 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-Stat-Signature: u5nbhnyzqcim5kr1cd9gkcuzutj1ww3r X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 30C851C001E X-Rspam-User: X-HE-Tag: 1712850412-820905 X-HE-Meta: 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 kbIuJF9t 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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 11.04.24 17:32, Zi Yan wrote: > From: Zi Yan > > In __folio_remove_rmap(), a large folio is added to deferred split list > if any page in a folio loses its final mapping. It is possible that > the folio is unmapped fully, but it is unnecessary to add the folio > to deferred split list at all. Fix it by checking folio mapcount before > adding a folio to deferred split list. > > Signed-off-by: Zi Yan > --- > mm/rmap.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 2608c40dffad..d599a772e282 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1494,7 +1494,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > enum rmap_level level) > { > atomic_t *mapped = &folio->_nr_pages_mapped; > - int last, nr = 0, nr_pmdmapped = 0; > + int last, nr = 0, nr_pmdmapped = 0, mapcount = 0; > enum node_stat_item idx; > > __folio_rmap_sanity_checks(folio, page, nr_pages, level); > @@ -1506,7 +1506,8 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > break; > } > > - atomic_sub(nr_pages, &folio->_large_mapcount); > + mapcount = atomic_sub_return(nr_pages, > + &folio->_large_mapcount) + 1; That becomes a new memory barrier on some archs. Rather just re-read it below. Re-reading should be fine here. > do { > last = atomic_add_negative(-1, &page->_mapcount); > if (last) { > @@ -1554,7 +1555,9 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > * is still mapped. > */ > if (folio_test_large(folio) && folio_test_anon(folio)) > - if (level == RMAP_LEVEL_PTE || nr < nr_pmdmapped) > + if ((level == RMAP_LEVEL_PTE && > + mapcount != 0) || > + (level == RMAP_LEVEL_PMD && nr < nr_pmdmapped)) > deferred_split_folio(folio); > } But I do wonder if we really care? Usually the folio will simply get freed afterwards, where we simply remove it from the list. If it's pinned, we won't be able to free or reclaim, but it's rather a corner case ... Is it really worth the added code? Not convinced. -- Cheers, David / dhildenb