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imf12.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf12.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1708067288; a=rsa-sha256; cv=none; b=T0m+FbBKeRZN+E0vVFOnSyFdmRC+U9cwaStcxGMAjAjLLyXEoYuBtbvOZ9V0ldVDTFr+39 WWOjI9yLk2UJQKJwknBzW64bTnQEUzFeYsa9orNJEDEXw4alVaeL56O5FwyC57ImqWbW8Z djnQCU1E9haq4dVehCe/rzR/yXMflNw= X-AuditID: a67dfc5b-d6dff70000001748-87-65cf09cf730f Date: Fri, 16 Feb 2024 16:07:54 +0900 From: Byungchul Park To: Oscar Salvador Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org Subject: Re: [PATCH] sched/numa, mm: do not promote folios to nodes not set N_MEMORY Message-ID: <20240216070754.GB32626@system.software.com> References: <20240214035355.18335-1-byungchul@sk.com> MIME-Version: 1.0 Content-Type: text/plain; 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It's because of null pointers of ->zone_pgdat of zones of > > those nodes that are not initialized at booting time. So should avoid > > nodes not set N_MEMORY from getting promoted. > > Looking at free_area_init(), we call free_area_init_node() for each node > found on the system. > And free_area_init_node()->free_area_init_core() inits all zones > belonging to the system via zone_init_internals(). For normal numa nodes, node_data[] is initialized at alloc_node_data(), but it's not for memoryless node. However, the node *gets onlined* at init_cpu_to_node(). Let's look at back free_area_init(). free_area_init_node() will be called with node_data[] not set yet, because it's already *onlined*. So ->zone_pgdat cannot be initialized properly in the path you mentioned. Byungchul > Now, I am not saying the check is wrong because we obviously do not want > migrate memory to a memoryless node, but I am confused as to where > we are crashing. > > > -- > Oscar Salvador > SUSE Labs