Commit b17c7035 authored by Paul E. McKenney's avatar Paul E. McKenney

rcu: Shrink RCU based on number of CPUs

Currently, rcu_init_geometry() only reshapes RCU's combining trees
if the leaf fanout is changed at boot time.  This means that by
default, kernels compiled with (say) NR_CPUS=4096 will keep oversized
data structures, even when running on systems with (say) four CPUs.

This commit therefore checks to see if the maximum number of CPUs on
the actual running system (nr_cpu_ids) differs from NR_CPUS, and if so
reshapes the combining trees accordingly.
Reported-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 4dbd6bb3
...@@ -2821,7 +2821,8 @@ static void __init rcu_init_geometry(void) ...@@ -2821,7 +2821,8 @@ static void __init rcu_init_geometry(void)
int rcu_capacity[MAX_RCU_LVLS + 1]; int rcu_capacity[MAX_RCU_LVLS + 1];
/* If the compile-time values are accurate, just leave. */ /* If the compile-time values are accurate, just leave. */
if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF) if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
nr_cpu_ids == NR_CPUS)
return; return;
/* /*
......
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