From: Paul E. McKenney Date: Thu, 6 Sep 2012 22:38:02 +0000 (-0700) Subject: rcu: Shrink RCU based on number of CPUs X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=b17c7035f37f47c7f7cb08a5555ab2aebfa31f91;p=openwrt%2Fstaging%2Fblogic.git 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: Mike Galbraith Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 8b9496fee235..b703989148e4 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -2821,7 +2821,8 @@ static void __init rcu_init_geometry(void) int rcu_capacity[MAX_RCU_LVLS + 1]; /* 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; /*