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[2003:cb:c729:d800:d3b6:a549:7878:a6ee]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42caf33e9b2sm65306325e9.14.2024.09.08.23.52.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 08 Sep 2024 23:52:50 -0700 (PDT) Message-ID: <6e02b962-14e2-48d3-ab26-d6de38dd9eda@redhat.com> Date: Mon, 9 Sep 2024 08:52:49 +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] mm: shmem: fix khugepaged activation policy for shmem To: Ryan Roberts , Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, 21cnbao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <7c796904528e21152ba5aa639e963e0ae45b7040.1725600217.git.baolin.wang@linux.alibaba.com> <58cf63c1-25e5-4958-96cb-a9d65390ca3e@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: <58cf63c1-25e5-4958-96cb-a9d65390ca3e@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 06.09.24 10:55, Ryan Roberts wrote: > On 06/09/2024 06:28, Baolin Wang wrote: >> Shmem has a separate interface (different from anonymous pages) to control >> huge page allocation, that means shmem THP can be enabled while anonymous >> THP is disabled. However, in this case, khugepaged will not start to collapse >> shmem THP, which is unreasonable. >> >> To fix this issue, we should call start_stop_khugepaged() to activate or >> deactivate the khugepaged thread when setting shmem mTHP interfaces. >> Moreover, add a new helper shmem_hpage_pmd_enabled() to help to check >> whether shmem THP is enabled, which will determine if khugepaged should >> be activated. >> >> Reported-by: Ryan Roberts >> Signed-off-by: Baolin Wang >> --- >> Hi Ryan, >> >> I remember we discussed the shmem khugepaged activation issue before, but >> I haven’t seen any follow-up patches to fix it. Recently, I am trying to >> fix the shmem mTHP collapse issue in the series [1], and I also addressed >> this activation issue. Please correct me if you have a better idea. Thanks. > > Thanks for for sorting this - it looks like a good approach to me! Just a couple > of nits. Regardless: > > Reviewed-by: Ryan Roberts > >> >> [1] https://lore.kernel.org/all/cover.1724140601.git.baolin.wang@linux.alibaba.com/T/#u >> --- >> include/linux/shmem_fs.h | 6 ++++++ >> mm/khugepaged.c | 2 ++ >> mm/shmem.c | 29 +++++++++++++++++++++++++++-- >> 3 files changed, 35 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h >> index 515a9a6a3c6f..ee6635052383 100644 >> --- a/include/linux/shmem_fs.h >> +++ b/include/linux/shmem_fs.h >> @@ -114,6 +114,7 @@ int shmem_unuse(unsigned int type); >> unsigned long shmem_allowable_huge_orders(struct inode *inode, >> struct vm_area_struct *vma, pgoff_t index, >> loff_t write_end, bool shmem_huge_force); >> +bool shmem_hpage_pmd_enabled(void); >> #else >> static inline unsigned long shmem_allowable_huge_orders(struct inode *inode, >> struct vm_area_struct *vma, pgoff_t index, >> @@ -121,6 +122,11 @@ static inline unsigned long shmem_allowable_huge_orders(struct inode *inode, >> { >> return 0; >> } >> + >> +static inline bool shmem_hpage_pmd_enabled(void) >> +{ >> + return false; >> +} >> #endif >> >> #ifdef CONFIG_SHMEM >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index f9c39898eaff..caf10096d4d1 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -430,6 +430,8 @@ static bool hugepage_pmd_enabled(void) >> if (test_bit(PMD_ORDER, &huge_anon_orders_inherit) && >> hugepage_global_enabled()) >> return true; >> + if (shmem_hpage_pmd_enabled()) >> + return true; > > nit: There is a comment at the top of this function, perhaps that could be > extended to cover shmem too? > >> return false; >> } >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 74f093d88c78..d7c342ae2b37 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -1653,6 +1653,23 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp) >> } >> >> #ifdef CONFIG_TRANSPARENT_HUGEPAGE >> +bool shmem_hpage_pmd_enabled(void) >> +{ >> + if (shmem_huge == SHMEM_HUGE_DENY) >> + return false; >> + if (test_bit(HPAGE_PMD_ORDER, &huge_shmem_orders_always)) > > question: When is it correct to use HPAGE_PMD_ORDER vs PMD_ORDER? I tend to use > PMD_ORDER (in hugepage_pmd_enabled() for example). I think the HPAGE_PMD_ORDER thingy originally was introduced to detect code that is supposed to handle THPs, but really cannot handle them properly -- e.g., no arch support, not enabled in the kernel config. My take is that we should start removing this HPAGE_* stuff. -- Cheers, David / dhildenb