From c2baef394af88af19e3945f861145679e92ff3e4 Mon Sep 17 00:00:00 2001 From: Qi Zheng Date: Thu, 19 Oct 2023 18:43:54 +0800 Subject: [PATCH] mm: page_alloc: skip memoryless nodes entirely Patch series "handle memoryless nodes more appropriately", v3. 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. This patch (of 2): In find_next_best_node(), we skipped the memoryless nodes when building the zonelists of other normal nodes (N_NORMAL), but did not skip the memoryless node itself when building the zonelist. This will cause it to be traversed at runtime. For example, say we have node0 and node1, node0 is memoryless node, then the fallback order of node0 and node1 as follows: [ 0.153005] Fallback order for Node 0: 0 1 [ 0.153564] Fallback order for Node 1: 1 After this patch, we skip memoryless node0 entirely, then the fallback order of node0 and node1 as follows: [ 0.155236] Fallback order for Node 0: 1 [ 0.155806] Fallback order for Node 1: 1 So it becomes completely invisible, which will reduce runtime overhead. And in this way, we will not try to allocate pages from memoryless node0, then the panic mentioned in [1] will also be fixed. Even though this problem has been solved by dropping the NODE_MIN_SIZE constrain in x86 [2], it would be better to fix it in core MM as well. [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/ [zhengqi.arch@bytedance.com: update comment, per Ingo] Link: https://lkml.kernel.org/r/7300fc00a057eefeb9a68c8ad28171c3f0ce66ce.1697799303.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/cover.1697799303.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/cover.1697711415.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/157013e978468241de4a4c05d5337a44638ecb0e.1697711415.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Acked-by: David Hildenbrand Acked-by: Ingo Molnar Cc: Aneesh Kumar K.V Cc: "Huang, Ying" Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/page_alloc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d52718284029..aa90758950a7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5020,8 +5020,11 @@ int find_next_best_node(int node, nodemask_t *used_node_mask) int min_val = INT_MAX; int best_node = NUMA_NO_NODE; - /* Use the local node if we haven't already */ - if (!node_isset(node, *used_node_mask)) { + /* + * Use the local node if we haven't already, but for memoryless local + * node, we should skip it and fall back to other nodes. + */ + if (!node_isset(node, *used_node_mask) && node_state(node, N_MEMORY)) { node_set(node, *used_node_mask); return node; }