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Wed, 15 Feb 2023 15:11:27 -0800 (PST) Received: from [10.200.11.190] ([139.177.225.228]) by smtp.gmail.com with ESMTPSA id g2-20020a62e302000000b005a7f8a326a3sm7128156pfh.50.2023.02.15.15.11.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Feb 2023 15:11:26 -0800 (PST) Message-ID: <3426457c-99bf-9f7c-f663-c29474d9fa73@bytedance.com> Date: Thu, 16 Feb 2023 07:11:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 Subject: Re: [PATCH 0/2] handle memoryless nodes more appropriately Content-Language: en-US To: Michal Hocko Cc: akpm@linux-foundation.org, vbabka@suse.cz, david@redhat.com, rppt@kernel.org, willy@infradead.org, mgorman@techsingularity.net, osalvador@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song References: <20230215152412.13368-1-zhengqi.arch@bytedance.com> From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 1tjrc6oesfd4oog7s3y5pwcc18x6e9m5 X-Rspamd-Queue-Id: 610EDC0013 X-HE-Tag: 1676502688-720259 X-HE-Meta: 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 61IhUPlz 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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: On 2023/2/16 00:36, Michal Hocko wrote: > On Wed 15-02-23 23:24:10, Qi Zheng wrote: >> Hi all, >> >> Currently, in the process of initialization or offline memory, memoryless >> nodes will still be built into the fallback list of itself or other nodes. >> >> This is not what we expected, so this patch series removes memoryless >> nodes from the fallback list entirely. >> >> Comments and suggestions are welcome. Hi Michal, > > This is a tricky area full of surprises and it is really easy to Would you mind giving an example of a "new problem"? > introduce new problems. What kind of problem/issue are you trying to > solve/handle by these changes? IIUC, I think there are two reasons: Firstly, as mentioned in commit message, the memoryless node has no memory to allocate (If it can be allocated, it may also cause the panic I mentioned in [1]), so we should not continue to traverse it when allocating memory at runtime, which will have a certain overhead. Secondly, from the perspective of semantic correctness, why do we remove the memoryless node from the fallback list of other normal nodes (N_MEMORY), but not from its own fallback list (PATCH[1/2])? Why should an upcoming memoryless node continue exist in the fallback list of itself and other normal nodes (PATCH[2/2])? Please let me know if I missed something. [1] https://lore.kernel.org/lkml/20230212110305.93670-1-zhengqi.arch@bytedance.com/ Thanks, Qi >