From 8219fc48adb3b09eabf502c560bf13f273ea69a3 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Wed, 12 Dec 2012 13:51:21 -0800 Subject: [PATCH] mm: node_states: introduce N_MEMORY We have N_NORMAL_MEMORY for standing for the nodes that have normal memory with zone_type <= ZONE_NORMAL. And we have N_HIGH_MEMORY for standing for the nodes that have normal or high memory. But we don't have any word to stand for the nodes that have *any* memory. And we have N_CPU but without N_MEMORY. Current code reuse the N_HIGH_MEMORY for this purpose because any node which has memory must have high memory or normal memory currently. A) But this reusing is bad for *readability*. Because the name N_HIGH_MEMORY just stands for high or normal: A.example 1) mem_cgroup_nr_lru_pages(): for_each_node_state(nid, N_HIGH_MEMORY) The user will be confused(why this function just counts for high or normal memory node? does it counts for ZONE_MOVABLE's lru pages?) until someone else tell them N_HIGH_MEMORY is reused to stand for nodes that have any memory. A.cont) If we introduce N_MEMORY, we can reduce this confusing AND make the code more clearly: A.example 2) mm/page_cgroup.c use N_HIGH_MEMORY twice: One is in page_cgroup_init(void): for_each_node_state(nid, N_HIGH_MEMORY) { It means if the node have memory, we will allocate page_cgroup map for the node. We should use N_MEMORY instead here to gaim more clearly. The second using is in alloc_page_cgroup(): if (node_state(nid, N_HIGH_MEMORY)) addr = vzalloc_node(size, nid); It means if the node has high or normal memory that can be allocated from kernel. We should keep N_HIGH_MEMORY here, and it will be better if the "any memory" semantic of N_HIGH_MEMORY is removed. B) This reusing is out-dated if we introduce MOVABLE-dedicated node. The MOVABLE-dedicated node should not appear in node_stats[N_HIGH_MEMORY] nor node_stats[N_NORMAL_MEMORY], because MOVABLE-dedicated node has no high or normal memory. In x86_64, N_HIGH_MEMORY=N_NORMAL_MEMORY, if a MOVABLE-dedicated node is in node_stats[N_HIGH_MEMORY], it is also means it is in node_stats[N_NORMAL_MEMORY], it causes SLUB wrong. The slub uses for_each_node_state(nid, N_NORMAL_MEMORY) and creates kmem_cache_node for MOVABLE-dedicated node and cause problem. In one word, we need a N_MEMORY. We just intrude it as an alias to N_HIGH_MEMORY and fix all im-proper usages of N_HIGH_MEMORY in late patches. Signed-off-by: Lai Jiangshan Acked-by: Christoph Lameter Acked-by: Hillf Danton Signed-off-by: Wen Congyang Cc: Lin Feng Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/nodemask.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 7afc36334d52..c6ebdc97a428 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -380,6 +380,7 @@ enum node_states { #else N_HIGH_MEMORY = N_NORMAL_MEMORY, #endif + N_MEMORY = N_HIGH_MEMORY, N_CPU, /* The node has one or more cpus */ NR_NODE_STATES }; -- 2.39.2