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[2003:cb:c71c:4e00:b097:7075:f6ba:300a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-429059a564asm118053785e9.32.2024.08.09.01.39.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Aug 2024 01:39:14 -0700 (PDT) Message-ID: <537d7a30-2ad8-4c31-9ad3-ad86f1a7b519@redhat.com> Date: Fri, 9 Aug 2024 10:39:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 1/2] mm: collect the number of anon large folios To: Ryan Roberts , Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: chrisl@kernel.org, kaleshsingh@google.com, kasong@tencent.com, linux-kernel@vger.kernel.org, ioworker0@gmail.com, baolin.wang@linux.alibaba.com, ziy@nvidia.com, hanchuanhua@oppo.com, Barry Song References: <20240808010457.228753-1-21cnbao@gmail.com> <20240808010457.228753-2-21cnbao@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: 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-Stat-Signature: 74wnb9ytt5odxyu13fgacphapun85xb6 X-Rspamd-Queue-Id: DF44380019 X-Rspamd-Server: rspam11 X-HE-Tag: 1723192759-901382 X-HE-Meta: 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 6KFLg+L/ Jwkt5B8P+z8ynJHGpkUP3k2rVSI4k/CBieYyLGpyjrkmnh4T8IWZ/Vke8IL3HgVleVHwIQrkXBcN8AyMpWNiw4RXroenEFg6zbrvLwBbaOWp97KFB5MFau9YsPOLpQungzC3YesX0bt12c0xB2npiobqQALQ1EfhMcpjX6BtGeAt5/1gdFysYR22RIONpW1vVv8OnffPxbj/6EnvW5/fw8EJKn0fMPA2mgKFZKD+EZ/AudBAPJJMjcE/tJdUeAXhC+oP39/1HcAHZAQ2UO5Vpenk6HmkadxYl36z951PfLuznzn5gC45t+2WDbdm2j1sXM9ImAAOFqNU5iXcqd/opOwoK45VgvDflh+eaLlwfMFc8XQVgej7P05006VGauaaB6G3d1xtcijbIftok2Zg6ioCvqN2b2taDKmtI0qRjeuIIx0WGSbK3eopENg== 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 09.08.24 10:13, Ryan Roberts wrote: > On 08/08/2024 02:04, Barry Song wrote: >> From: Barry Song >> >> When a new anonymous mTHP is added to the rmap, we increase the count. >> We reduce the count whenever an mTHP is completely unmapped. >> >> Signed-off-by: Barry Song >> --- >> Documentation/admin-guide/mm/transhuge.rst | 5 +++++ >> include/linux/huge_mm.h | 15 +++++++++++++-- >> mm/huge_memory.c | 2 ++ >> mm/rmap.c | 3 +++ >> 4 files changed, 23 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst >> index 058485daf186..715f181543f6 100644 >> --- a/Documentation/admin-guide/mm/transhuge.rst >> +++ b/Documentation/admin-guide/mm/transhuge.rst >> @@ -527,6 +527,11 @@ split_deferred >> it would free up some memory. Pages on split queue are going to >> be split under memory pressure, if splitting is possible. >> >> +anon_num >> + the number of anon huge pages we have in the whole system. >> + These huge pages could be still entirely mapped and have partially >> + unmapped and unused subpages. > > nit: "entirely mapped and have partially unmapped and unused subpages" -> > "entirely mapped or have partially unmapped/unused subpages" > >> + >> As the system ages, allocating huge pages may be expensive as the >> system uses memory compaction to copy data around memory to free a >> huge page for use. There are some counters in ``/proc/vmstat`` to help >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index e25d9ebfdf89..294c348fe3cc 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -281,6 +281,7 @@ enum mthp_stat_item { >> MTHP_STAT_SPLIT, >> MTHP_STAT_SPLIT_FAILED, >> MTHP_STAT_SPLIT_DEFERRED, >> + MTHP_STAT_NR_ANON, >> __MTHP_STAT_COUNT >> }; >> >> @@ -291,14 +292,24 @@ struct mthp_stat { >> #ifdef CONFIG_SYSFS >> DECLARE_PER_CPU(struct mthp_stat, mthp_stats); >> >> -static inline void count_mthp_stat(int order, enum mthp_stat_item item) >> +static inline void mod_mthp_stat(int order, enum mthp_stat_item item, int delta) >> { >> if (order <= 0 || order > PMD_ORDER) >> return; >> >> - this_cpu_inc(mthp_stats.stats[order][item]); >> + this_cpu_add(mthp_stats.stats[order][item], delta); >> +} >> + >> +static inline void count_mthp_stat(int order, enum mthp_stat_item item) >> +{ >> + mod_mthp_stat(order, item, 1); >> } >> + >> #else >> +static inline void mod_mthp_stat(int order, enum mthp_stat_item item, int delta) >> +{ >> +} >> + >> static inline void count_mthp_stat(int order, enum mthp_stat_item item) >> { >> } >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 697fcf89f975..b6bc2a3791e3 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -578,6 +578,7 @@ DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE); >> DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT); >> DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED); >> DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED); >> +DEFINE_MTHP_STAT_ATTR(anon_num, MTHP_STAT_NR_ANON); >> >> static struct attribute *stats_attrs[] = { >> &anon_fault_alloc_attr.attr, >> @@ -591,6 +592,7 @@ static struct attribute *stats_attrs[] = { >> &split_attr.attr, >> &split_failed_attr.attr, >> &split_deferred_attr.attr, >> + &anon_num_attr.attr, >> NULL, >> }; >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 901950200957..2b722f26224c 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1467,6 +1467,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, >> } >> >> __folio_mod_stat(folio, nr, nr_pmdmapped); >> + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); >> } >> >> static __always_inline void __folio_add_file_rmap(struct folio *folio, >> @@ -1582,6 +1583,8 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, >> list_empty(&folio->_deferred_list)) >> deferred_split_folio(folio); >> __folio_mod_stat(folio, -nr, -nr_pmdmapped); >> + if (folio_test_anon(folio) && !atomic_read(mapped)) > > Agree that atomic_read() is dodgy here. > > Not sure I fully understand why David prefers to do the unaccounting at > free-time though? It feels unbalanced to me to increment when first mapped but > decrement when freed. Surely its safer to either use alloc/free or use first > map/last map? Doing it when we set/clear folio->mapping is straight forward. Anon folios currently come to live when we first map them, and they stay that way until we free them. In the future, we'll have to move that anon handling further out, when if have to allocate anon-specific memdesc ahead of time, then, it will be clued to that lifetime. > > If using alloc/free isn't there a THP constructor/destructor that prepares the > deferred list? (My memory may be failing me). Could we use that? Likely the deconstructor could work as well. Not sure if that is any better than the freeing path where folio->mapping currently gets cleared. The generic constructor certainly won't work right now. That's not where the "anon" part comes to live. Let's take a look how NR_FILE_THPS is handled: __filemap_add_folio() increments it -- when we set folio->mapping __filemap_remove_folio() (->filemap_unaccount_folio) decrements it -- after which we usually call page_cache_delete() to set folio->mapping = NULL; -- Cheers, David / dhildenb