Messages in this thread Patch in this message | | | Date | Mon, 29 Aug 2016 10:59:23 -0700 | From | Tim Chen <> | Subject | [PATCH v2] cpu: Fix node state for whether it contains CPU |
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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.
v2: 1. Fix the problem for all architectures in the generic path inside vmstat, not just for x86.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> --- mm/vmstat.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/mm/vmstat.c b/mm/vmstat.c index 89cec42..d83f953 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1794,6 +1794,16 @@ 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; @@ -1851,6 +1861,7 @@ 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(); -- 2.5.5
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