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[2003:d8:2f20:7500:5f99:9633:990e:138]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4589ee57922sm57069765e9.22.2025.08.01.02.04.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 Aug 2025 02:04:01 -0700 (PDT) Message-ID: <3939866f-e57e-4caa-919a-558bf6866b82@redhat.com> Date: Fri, 1 Aug 2025 11:04:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mempolicy: Clarify what zone reclaim means To: SeongJae Park , Joshua Hahn Cc: Andrew Morton , Ying Huang , Zi Yan , Johannes Weiner , Matthew Brost , Rakie Kim , Byungchul Park , Gregory Price , Alistair Popple , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com References: <20250731224155.1646-1-sj@kernel.org> 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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <20250731224155.1646-1-sj@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Q-B3PYSpAyxyOyhbOYnEoNRhgBxQSt2q8XDW5R1kbLw_1754039043 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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C6A6C40011 X-Stat-Signature: dh9w7g36bqnaxhmn4d7xo98qgiuthmfk X-HE-Tag: 1754039047-907168 X-HE-Meta: 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 SIEDQLCd 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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 01.08.25 00:41, SeongJae Park wrote: > On Thu, 31 Jul 2025 14:07:37 -0700 Joshua Hahn wrote: > >> The zone_reclaim_mode API controls the reclaim behavior when a node runs out of >> memory. Contrary to its user-facing name, it is internally referred to as >> "node_reclaim_mode". >> >> This can be confusing. But because we cannot change the name of the API since >> it has been in place since at least 2.6, let's try to be more explicit about >> what the behavior of this API is. >> >> Change the description to clarify what zone reclaim entails, and be explicit >> about the RECLAIM_ZONE bit, whose purpose has led to some confusion in the >> past already [1] [2]. >> >> [1] https://lore.kernel.org/linux-mm/1579005573-58923-1-git-send-email-alex.shi@linux.alibaba.com/ >> [2] https://lore.kernel.org/linux-mm/20200626003459.D8E015CA@viggo.jf.intel.com/ >> >> Signed-off-by: Joshua Hahn >> --- >> include/uapi/linux/mempolicy.h | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h >> index 1f9bb10d1a47..6c9c9385ff89 100644 >> --- a/include/uapi/linux/mempolicy.h >> +++ b/include/uapi/linux/mempolicy.h >> @@ -66,10 +66,16 @@ enum { >> #define MPOL_F_MORON (1 << 4) /* Migrate On protnone Reference On Node */ >> >> /* >> + * Enabling zone reclaim means the page allocator will attempt to fulfill >> + * the allocation request on the current node by triggering reclaim and >> + * trying to shrink the current node. >> + * Fallback allocations on the next candidates in the zonelist are considered >> + * zone when reclaim fails to free up enough memory in the current node/zone. > > s/zone when reclaim fails/when reclaim fails/ ? Agreed, that confused me as well. Acked-by: David Hildenbrand -- Cheers, David / dhildenb