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Tue, 09 Jul 2024 21:04:29 -0700 (PDT) Received: from [172.20.2.228] ([4.28.11.157]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ca353ccedasm2701287a91.57.2024.07.09.21.04.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 21:04:28 -0700 (PDT) Message-ID: <9d77dc44-f61c-4e52-938f-c268daf0e169@redhat.com> Date: Wed, 10 Jul 2024 06:04:27 +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> Cc: akpm@linux-foundation.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: 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-Queue-Id: 4697E8001D X-Stat-Signature: e6kjsyos81shk9xmjcxg41bdrarhu97b X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1720584277-977093 X-HE-Meta: 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 tKCMbZ4m 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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 06:02, Barry Song wrote: > On Wed, Jul 10, 2024 at 3:59 PM David Hildenbrand wrote: >> >> 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()? > > my point is that the purpose is skipping redundant swap-out, if shmem is single > mapped, they could be also skipped. But they won't get necessarily *freed* when unmapping them. They might just continue living in tmpfs? where some other process might just map them later? IMHO, there is a big difference here between anon and shmem. (well, anon_shmem would actually be different :) ) -- Cheers, David / dhildenb