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Tue, 09 Jul 2024 20:59:03 -0700 (PDT) Received: from [172.20.2.228] ([4.28.11.157]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6ac0841sm23425215ad.211.2024.07.09.20.59.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 20:59:02 -0700 (PDT) Message-ID: Date: Wed, 10 Jul 2024 05:59:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7] mm: shrink skip folio mapped by an exiting process To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org Cc: baohua@kernel.org, justinjiang@vivo.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, opensource.kernel@vivo.com, willy@infradead.org References: <20240709142312.372b20d49c6a97ecd2cd9904@linux-foundation.org> <20240710033212.36497-1-21cnbao@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: <20240710033212.36497-1-21cnbao@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: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A322440003 X-Stat-Signature: oxk9q8d3a1oti68qsa8ddufmoessmsc1 X-Rspam-User: X-HE-Tag: 1720583946-135973 X-HE-Meta: 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 cn2OzwDe 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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 10.07.24 05:32, Barry Song wrote: > On Wed, Jul 10, 2024 at 9:23 AM Andrew Morton wrote: >> >> On Tue,  9 Jul 2024 20:31:15 +0800 Zhiguo Jiang wrote: >> >>> The releasing process of the non-shared anonymous folio mapped solely by >>> an exiting process may go through two flows: 1) the anonymous folio is >>> firstly is swaped-out into swapspace and transformed into a swp_entry >>> in shrink_folio_list; 2) then the swp_entry is released in the process >>> exiting flow. This will result in the high cpu load of releasing a >>> non-shared anonymous folio mapped solely by an exiting process. >>> >>> When the low system memory and the exiting process exist at the same >>> time, it will be likely to happen, because the non-shared anonymous >>> folio mapped solely by an exiting process may be reclaimed by >>> shrink_folio_list. >>> >>> This patch is that shrink skips the non-shared anonymous folio solely >>> mapped by an exting process and this folio is only released directly in >>> the process exiting flow, which will save swap-out time and alleviate >>> the load of the process exiting. >> >> It would be helpful to provide some before-and-after runtime >> measurements, please.  It's a performance optimization so please let's >> see what effect it has. > > Hi Andrew, > > This was something I was curious about too, so I created a small test program > that allocates and continuously writes to 256MB of memory. Using QEMU, I set > up a small machine with only 300MB of RAM to trigger kswapd. > > qemu-system-aarch64 -M virt,gic-version=3,mte=off -nographic \ > -smp cpus=4 -cpu max \ > -m 300M -kernel arch/arm64/boot/Image > > The test program will be randomly terminated by its subprocess to trigger > the use case of this patch. > > #include > #include > #include > #include > #include > #include > #include > #include > > #define MEMORY_SIZE (256 * 1024 * 1024) > > unsigned char *memory; > > void allocate_and_write_memory() > { > memory = (unsigned char *)malloc(MEMORY_SIZE); > if (memory == NULL) { > perror("malloc"); > exit(EXIT_FAILURE); > } > > while (1) > memset(memory, 0x11, MEMORY_SIZE); > } > > int main() > { > pid_t pid; > srand(time(NULL)); > > pid = fork(); > > if (pid < 0) { > perror("fork"); > exit(EXIT_FAILURE); > } > > if (pid == 0) { > int delay = (rand() % 10000) + 10000; > usleep(delay * 1000); > > /* kill parent when it is busy on swapping */ > kill(getppid(), SIGKILL); > _exit(0); > } else { > allocate_and_write_memory(); > > wait(NULL); > > free(memory); > } > > return 0; > } > > I tracked the number of folios that could be redundantly > swapped out by adding a simple counter as shown below: > > @@ -879,6 +880,9 @@ static bool folio_referenced_one(struct folio *folio, > check_stable_address_space(vma->vm_mm)) && > folio_test_swapbacked(folio) && > !folio_likely_mapped_shared(folio)) { > + static long i, size; > + size += folio_size(folio); > + pr_err("index: %d skipped folio:%lx total size:%d\n", i++, (unsigned long)folio, size); > pra->referenced = -1; > page_vma_mapped_walk_done(&pvmw); > return false; > > > This is what I have observed: > > / # /home/barry/develop/linux/skip_swap_out_test > [ 82.925645] index: 0 skipped folio:fffffdffc0425400 total size:65536 > [ 82.925960] index: 1 skipped folio:fffffdffc0425800 total size:131072 > [ 82.927524] index: 2 skipped folio:fffffdffc0425c00 total size:196608 > [ 82.928649] index: 3 skipped folio:fffffdffc0426000 total size:262144 > [ 82.929383] index: 4 skipped folio:fffffdffc0426400 total size:327680 > [ 82.929995] index: 5 skipped folio:fffffdffc0426800 total size:393216 > ... > [ 88.469130] index: 6112 skipped folio:fffffdffc0390080 total size:97230848 > [ 88.469966] index: 6113 skipped folio:fffffdffc038d000 total size:97296384 > [ 89.023414] index: 6114 skipped folio:fffffdffc0366cc0 total size:97300480 > > I observed that this patch effectively skipped 6114 folios (either 4KB or 64KB > mTHP), potentially reducing the swap-out by up to 92MB (97,300,480 bytes) during > the process exit. > > Despite the numerous mistakes Zhiguo made in sending this patch, it is still > quite valuable. Please consider pulling his v9 into the mm tree for testing. BTW, we dropped the folio_test_anon() check, but what about shmem? They also do __folio_set_swapbacked()? -- Cheers, David / dhildenb