From 03e86dba5b628a13a58adae62e5b918b969ae93e Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Fri, 7 Oct 2016 17:00:02 -0700 Subject: [PATCH] cpu: fix node state for whether it contains CPU In current kernel code, we only call node_set_state(cpu_to_node(cpu), N_CPU) when a cpu is hot plugged. But we do not set the node state for N_CPU when the cpus are brought online during boot. So this could lead to failure when we check to see if a node contains cpu with node_state(node_id, N_CPU). One use case is in the node_reclaime function: /* * Only run node reclaim on the local node or on nodes that do * not * have associated processors. This will favor the local * processor * over remote processors and spread off node memory allocations * as wide as possible. */ if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) return NODE_RECLAIM_NOSCAN; I instrumented the kernel to call this function after boot and it always returns 0 on a x86 desktop machine until I apply the attached patch. int num_cpu_node(void) { int i, nr_cpu_nodes = 0; for_each_node(i) { if (node_state(i, N_CPU)) ++ nr_cpu_nodes; } return nr_cpu_nodes; } Fix this by checking each node for online CPU when we initialize vmstat that's responsible for maintaining node state. Link: http://lkml.kernel.org/r/20160829175922.GA21775@linux.intel.com Signed-off-by: Tim Chen Acked-by: David Rientjes Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: Tim Chen Cc: Cc: Ying Cc: Andi Kleen Cc: Dave Hansen Cc: Dan Williams Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmstat.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/vmstat.c b/mm/vmstat.c index dc04e76c7950..73aab319969d 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1715,6 +1715,16 @@ static void __init start_shepherd_timer(void) round_jiffies_relative(sysctl_stat_interval)); } +static void __init init_cpu_node_state(void) +{ + int cpu; + + get_online_cpus(); + for_each_online_cpu(cpu) + node_set_state(cpu_to_node(cpu), N_CPU); + put_online_cpus(); +} + static void vmstat_cpu_dead(int node) { int cpu; @@ -1772,6 +1782,7 @@ static int __init setup_vmstat(void) #ifdef CONFIG_SMP cpu_notifier_register_begin(); __register_cpu_notifier(&vmstat_notifier); + init_cpu_node_state(); start_shepherd_timer(); cpu_notifier_register_done(); -- 2.20.1