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Thu, 19 Oct 2023 01:17:55 -0700 (PDT) Received: from [10.84.155.153] ([203.208.167.147]) by smtp.gmail.com with ESMTPSA id a13-20020a65640d000000b005b458aa0541sm2500961pgv.15.2023.10.19.01.17.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Oct 2023 01:17:54 -0700 (PDT) Message-ID: Date: Thu, 19 Oct 2023 16:17:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v2 0/2] handle memoryless nodes more appropriately Content-Language: en-US To: David Hildenbrand Cc: akpm@linux-foundation.org, rppt@kernel.org, vbabka@suse.cz, mhocko@suse.com, willy@infradead.org, mgorman@techsingularity.net, mingo@kernel.org, aneesh.kumar@linux.ibm.com, ying.huang@intel.com, hannes@cmpxchg.org, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <2a3bd858-5464-4569-be1e-2a1867d90c15@redhat.com> From: Qi Zheng In-Reply-To: <2a3bd858-5464-4569-be1e-2a1867d90c15@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: utd1bwrkzag4oi5ss98emadscnffnh79 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7F5CBA0022 X-Rspam-User: X-HE-Tag: 1697703476-539184 X-HE-Meta: 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 DO8/beGn 6Yc0hVWWAIXmPdufIM2DFpPbYe+8pkWLtRK5O/A6twWAVEMIIzxxXHONOONtqGCPUllSkzyY5HDKaSI9+7cKn3F5gA4N4PcB8yMdTJMklku59qRawvGild5TWjL+tYj7yDdwXMtLBMKhtFlBQq4m8lEUn5o71EiynilH5YiwZondH/SLxkKbC3DYzylQWuX6EFeFtTP6KzQkhyKZ7HzCRgAJRhla7/LHbPV2CjJtG6WaDqidmhMGy3DMDM1PpzUl1bxevgFJjP8LZOoZ4ewDxskUqouURpyOercb/NcwyjEWvKgKojInAQeI1S+uofedu/+rHDphdrwtGDhnOT7nYmACUB6emOilQDBq+nRDN0U4MDxgOBZ3Zx4lF2g== 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: Hi David, On 2023/10/19 15:56, David Hildenbrand wrote: > On 19.10.23 09:36, 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. > > What's the end result of this change -- IOW why do we care? Patch #1 > mentions "which will reduce runtime overhead." and patch #2 mentions > "This will incur some runtime overhead.". IIUC the comment in patch #1 > correctly, these changes don't fix anything, correct? Yes, after dropping the NODE_MIN_SIZE constrain in x86, the panic problem fixed by this patch no longer exists (Unless there are other architectures that have this constrain). The reason I am re-sending this patch is that I agree with Ingo's point of view: ``` While I agree with dropping the limitation, and I agree that 9391a3f9c7f1 should have provided more of a justification, I believe a core MM fix is in order as well, for it to not crash. ``` I also think that core MM should be safe (not crash) even in some weird topology. > > Did you look into showing a performance gain? > No, and I think the performance gain should be small, after all it just traverses one less node. ;) Thanks, Qi