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[2003:cb:c719:8200:487a:3426:a17e:d7b7]) by smtp.gmail.com with ESMTPSA id k41-20020a05600c1ca900b00417e8be070csm26910729wms.9.2024.04.25.02.01.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Apr 2024 02:01:14 -0700 (PDT) Message-ID: <49394660-8455-48ec-8ae1-fbd2d590d27a@redhat.com> Date: Thu, 25 Apr 2024 11:01:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] mm/vmscan: avoid split PMD-mapped THP during shrink_folio_list() To: Lance Yang , ziy@nvidia.com Cc: 21cnbao@gmail.com, akpm@linux-foundation.org, fengwei.yin@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, maskray@google.com, mhocko@suse.com, minchan@kernel.org, peterx@redhat.com, ryan.roberts@arm.com, shy828301@gmail.com, songmuchun@bytedance.com, wangkefeng.wang@huawei.com, willy@infradead.org, xiehuan09@gmail.com, zokeefe@google.com References: <20240425085051.74889-1-ioworker0@gmail.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: <20240425085051.74889-1-ioworker0@gmail.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-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 296BDA001B X-Stat-Signature: moedn7xwt6yhqgn8ejibfqrjz4bki8g1 X-HE-Tag: 1714035678-907672 X-HE-Meta: U2FsdGVkX19T0Xx0Rd7E0rrnrZ0Vb41HdZJecvEDF2GUpVLQN04kL13Voi+y1N0K7OjA0qS1lRVi7V9gfqKzfKd71wDepM+TtPrs/xH00KhNyBkbQ7dPAKjBaAX37sEmn+z9XJWxFNOFcqmpajxGo4xdz12bpV9d5OeWsQCxYqxFFfPiguOFgShL7oqDpvNCuoSVMWzmnAAA5MTpimfyqDsNswhd/1GIZpyeLsVQAlT6c5zqFu6m9ITl++3wdHRBht+iJsUEdwT4LU5+Awsb9K735gZMT6f02BFdcPz0B8AgnxAXc/V/slmVs1JB2rMpHygoTiWmAlEt71lN7oDE/kO4LJfOAR8q1MjmAjAzMWmctykU0AmituypasNM1PiWbtpQg6qFcz/DUkGoKg3TD8IIta4GIadooJPAfZjm4faLoXRDoaK+Xo4M073qD7OnUxOI0bemXXQHsTQ+8f/8/NQzDqbqkQmz6NX5y5O8lrCzA5FmPxF4tinKKGhDhndBIzEUQ2aFZCaQJBiJgRYuy8c1B95wOs2x5EOPyJwcE3WiAKsbT7iYPm1Ysqaf6g6dqZqgdWmmejvwvg20fopG7aCuV6WlT2pQpCKmICy6sEELWbddyJcn8CbVOv7DIurPOZhoWw9YQAZ59qFwEBWrG3jGM5GbQ7eIQOPOz7lyRNb8/CwbxNVZpv6ilxl88HZcdAIOe9DYWk+PpQE/16B926B0MlkYOU5OTx5fOWmO1A/q7v/s97Ygwf9OKaA+FiT4T9aSJNTZpLYkw1UIZjF3gAPCTKBYjzpOZmbvnDmV4oQ30RKj5pHvonauI001J29DDLMCiXdSyXDeo4z14uEVFtqbRPzt+qcy6eQ9wkxFIhGpxyTN5iF9aWrTJ1v8Yv+OsEerJ+qOlONBkzmeuJyZvP9O9cQ+bin52p0jpwVsF7mgo2aV/pSqTFsKN8BgPh5RNURZAGm8yn+RWBL+d4P Ya6sjBhA gUUsISefIf2htep8edwx6osJ8kR5rvcEPD2JfGkLpofG53rCbJalKodAounH241nodt8ucz02s/o66mDBlCPqFpdqlSI/IpeSQcXzciJdp2g0eY76bkyQv9uUk4ip02KBrd8I7PgS43JpUupZdNMA8UQYs4TpVyNnStRSqZNbDWDY3HOY585AlfTeqjziOCFBepvb+O7xw0ltb12G2Gw3X6oYJw== 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 25.04.24 10:50, Lance Yang wrote: > Hey Zi, David, Hi, > > How about this change(diff against mm-unstable) as follows? goes into the right direction, please resent the whole thing, that will make it easier to review. > > I'd like to add __try_to_unmap_huge_pmd() as a new internal function > specifically for unmapping PMD-mapped folios. If, for any reason, we cannot > unmap the folio, then we'll still split it as previously done. > > Currently, __try_to_unmap_huge_pmd() only handles lazyfree THPs, but it > can be extended to support other large folios that are PMD-mapped in the > future if needed. > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 670218f762c8..0f906dc6d280 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -100,8 +100,6 @@ enum ttu_flags { > * do a final flush if necessary */ > TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: > * caller holds it */ > - TTU_LAZYFREE_THP = 0x100, /* avoid splitting PMD-mapped THPs > - * that are marked as lazyfree. */ > }; > > #ifdef CONFIG_MMU > diff --git a/mm/rmap.c b/mm/rmap.c > index a7913a454028..879c8923abfc 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1606,6 +1606,19 @@ void folio_remove_rmap_pmd(struct folio *folio, struct page *page, > #endif > } > > +static bool __try_to_unmap_huge_pmd(struct vm_area_struct *vma, > + unsigned long addr, struct folio *folio) > +{ > + VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > + if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) > + return discard_trans_pmd(vma, addr, folio); > +#endif > + > + return false; > +} > + > /* > * @arg: enum ttu_flags will be passed to this argument > */ > @@ -1631,14 +1644,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > if (flags & TTU_SYNC) > pvmw.flags = PVMW_SYNC; > > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (flags & TTU_LAZYFREE_THP) > - if (discard_trans_pmd(vma, address, folio)) > + if (flags & TTU_SPLIT_HUGE_PMD) { > + if (__try_to_unmap_huge_pmd(vma, address, folio)) > return true; > -#endif > - > - if (flags & TTU_SPLIT_HUGE_PMD) > split_huge_pmd_address(vma, address, false, folio); > + } > I was wondering if we can better integrate that into the pagewalk below. That is, don't do the TTU_SPLIT_HUGE_PMD immediately. Start the pagewalk first. If we walk a PMD, try to unmap it. Only if that fails, split it. Less working on "vma + address" and instead directly on PMDs. -- Cheers, David / dhildenb