diff options
Diffstat (limited to 'include/linux/topology.h')
| -rw-r--r-- | include/linux/topology.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/topology.h b/include/linux/topology.h index 47a3e3c08036..eb2fe6edd73c 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -27,6 +27,7 @@ #ifndef _LINUX_TOPOLOGY_H #define _LINUX_TOPOLOGY_H +#include <linux/arch_topology.h> #include <linux/cpumask.h> #include <linux/bitops.h> #include <linux/mmzone.h> @@ -59,6 +60,20 @@ int arch_update_cpu_topology(void); */ #define RECLAIM_DISTANCE 30 #endif + +/* + * The following tunable allows platforms to override the default node + * reclaim distance (RECLAIM_DISTANCE) if remote memory accesses are + * sufficiently fast that the default value actually hurts + * performance. + * + * AMD EPYC machines use this because even though the 2-hop distance + * is 32 (3.2x slower than a local memory access) performance actually + * *improves* if allowed to reclaim memory and load balance tasks + * between NUMA nodes 2-hops apart. + */ +extern int __read_mostly node_reclaim_distance; + #ifndef PENALTY_FOR_NODE_WITH_CPUS #define PENALTY_FOR_NODE_WITH_CPUS (1) #endif |