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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-381c10d4d82sm13124659f8f.45.2024.11.04.04.42.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Nov 2024 04:42:09 -0800 (PST) Message-ID: Date: Mon, 4 Nov 2024 13:42:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: count zeromap read and set for swapout and swapin To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , Usama Arif , Chengming Zhou , Yosry Ahmed , Nhat Pham , Johannes Weiner , Hugh Dickins , Matthew Wilcox , Shakeel Butt , Andi Kleen , Baolin Wang , Chris Li , "Huang, Ying" , Kairui Song , Ryan Roberts References: <20241102101240.35072-1-21cnbao@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: <20241102101240.35072-1-21cnbao@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-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 03706C001B X-Stat-Signature: r6t1rxhhmtm4iounmz4ttna9jzhs41u7 X-HE-Tag: 1730724119-589847 X-HE-Meta: U2FsdGVkX1+jXyCBUn5JIfwZFtN9/V/wWVKTurXyZlESHpGQ+F0Owy0OgehirrtzfKofx79ojPclYUouUcFnMvmkaLVo+dATpmfonXDAyuC9lGfMJ1reBLFM2E0EcroE21M5p5B5f0GGCztBDbbUld4HvqeYP6eSuLd1Xh4zFV5aoP+E1DMUCtqvbKsnU9NUusrB14GiPVuQ32DA7mtEk2Id0G9Q8vq87fPSaWV5AURVYtiarO+bXgOygZIIIxi7aIlHQaN4CPeF8kdl54vPN7OPmOOyRzaBNrer25mnrQPlkTkadtHkIIBnRrJrCfKZSPVxP2YMscCsxsrs5LZtcHIre4uM7/mnNCfu5SOdiOeuvDucwJdHXhMWABGZIcdb8hK6CPsLJ+k/KMEz5iv3gne9Gk+jOpcjgkUid5CaVnuPWc66xzbtVyeXIpHqpJijqJVXdtNM4iZeUT0hqm5WaOAwQ7GZ86Rb/tKHQZQ0an8V4z+gsLVEDklbdZrkXKJn71PSyu5rLD6SSDt7aZICQiTZCkvMliFL1Pq0pGthQJtMC+/xM/uDi6s6bADs7CCbjjKUXhLSmTHXbEcOMDMtl6r5NIsAB8DNoJxH3iOi0BHLVSdmXqpVEyadl6OqjfibfnqynzOEcTerk6OElHZ75FY/B+3oG2QuJoqW1wkugiIc0WLZb7it4mYDj+R+izUHwNCnJkOXN+abExgIXz9FwswUhLSwCsRwDF1P1ndKX0+OURkpGwAerNyxB14fQgUnK+ZbtWqUtXOuTIwRbsbbHYB+luWwxqMjLOL4UPK0zUhVLwxtD+RW5/dLpaWibs+jrvmDnDjby9fIcr3nwrtnbEBaGDBqqOOECawTFpQ550gYjuhTeIs6VSjtu8yajOideT/0eEHlCgUNRd8T07ewvYc5RxAzIqxYS81A00e8f9fCjMpe+3hDwNnsSHxfhf2unxVCBTAKM9E76oPzzV+ XCV4v3AA 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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 02.11.24 11:12, Barry Song wrote: > From: Barry Song > > When the proportion of folios from the zero map is small, missing their > accounting may not significantly impact profiling. However, it’s easy > to construct a scenario where this becomes an issue—for example, > allocating 1 GB of memory, writing zeros from userspace, followed by > MADV_PAGEOUT, and then swapping it back in. In this case, the swap-out > and swap-in counts seem to vanish into a black hole, potentially > causing semantic ambiguity. > > We have two ways to address this: > > 1. Add a separate counter specifically for the zero map. > 2. Continue using the current accounting, treating the zero map like > a normal backend. (This aligns with the current behavior of zRAM > when supporting same-page fills at the device level.) > > This patch adopts option 1 as pswpin/pswpout counters are that they > only apply to IO done directly to the backend device (as noted by > Nhat Pham). > > We can find these counters from /proc/vmstat (counters for the whole > system) and memcg's memory.stat (counters for the interested memcg). > > For example: > > $ grep -E 'swpin_zero|swpout_zero' /proc/vmstat > swpin_zero 1648 > swpout_zero 33536 > > $ grep -E 'swpin_zero|swpout_zero' /sys/fs/cgroup/system.slice/memory.stat > swpin_zero 3905 > swpout_zero 3985 > > Fixes: 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap") > Cc: Usama Arif > Cc: Chengming Zhou > Cc: Yosry Ahmed > Cc: Nhat Pham > Cc: Johannes Weiner > Cc: David Hildenbrand > Cc: Hugh Dickins > Cc: Matthew Wilcox (Oracle) > Cc: Shakeel Butt > Cc: Andi Kleen > Cc: Baolin Wang > Cc: Chris Li > Cc: "Huang, Ying" > Cc: Kairui Song > Cc: Ryan Roberts > Signed-off-by: Barry Song > --- > -v2: > * add separate counters rather than using pswpin/out; thanks > for the comments from Usama, David, Yosry and Nhat; > * Usama also suggested a new counter like swapped_zero, I > prefer that one be separated as an enhancement patch not > a hotfix. will probably handle it later on. > > Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++++ > include/linux/vm_event_item.h | 2 ++ > mm/memcontrol.c | 4 ++++ > mm/page_io.c | 16 ++++++++++++++++ > mm/vmstat.c | 2 ++ > 5 files changed, 34 insertions(+) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index db3799f1483e..984eb3c9d05b 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1599,6 +1599,16 @@ The following nested keys are defined. > pglazyfreed (npn) > Amount of reclaimed lazyfree pages > > + swpin_zero > + Number of pages moved into memory with zero content, meaning no > + copy exists in the backend swapfile, allowing swap-in to avoid > + I/O read overhead. > + > + swpout_zero > + Number of pages moved out of memory with zero content, meaning no > + copy is needed in the backend swapfile, allowing swap-out to avoid > + I/O write overhead. Hm, can make it a bit clearer that this is a pure optimization and refer to the other counters? swpin_zero Portion of "pswpin" pages for which I/O was optimized out because the page content was detected to be zero during swapout. swpout_zero Portion of "pswout" pages for which I/O was optimized out because the page content was detected to be zero. -- Cheers, David / dhildenb