rcu: Size rcu_node tree from nr_cpu_ids rather than NR_CPUS

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The rcu_node tree array is sized based on compile-time constants,
including NR_CPUS.  Although this approach has worked well in the past,
the recent trend by many distros to define NR_CPUS=4096 results in
excessive grace-period-initialization latencies.

This commit therefore substitutes the run-time computed nr_cpu_ids for
the compile-time NR_CPUS when building the tree.  This can result in
much of the compile-time-allocated rcu_node array being unused.  If
this is a major problem, you are in a specialized situation anyway,
so you can manually adjust the NR_CPUS, RCU_FANOUT, and RCU_FANOUT_LEAF
kernel config parameters.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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This commit is contained in:

Paul E. McKenney 2012-05-08 21:00:28 -07:00

parent cc5df65b03

commit cca6f39319

2 changed files with 3 additions and 1 deletions

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kernel/rcutree.c

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kernel/rcutree_plugin.h

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