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rcu: Control RCU_FANOUT_LEAF from boot-time parameter

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Although making RCU_FANOUT_LEAF a kernel configuration parameter rather
than a fixed constant makes it easier for people to decrease cache-miss
overhead for large systems, it is of little help for people who must
run a single pre-built kernel binary.

This commit therefore allows the value of RCU_FANOUT_LEAF to be
increased (but not decreased!) via a boot-time parameter named
rcutree.rcu_fanout_leaf.

Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2012-04-23 15:52:53 -07:00
parent cba6d0d64e
commit f885b7f2b2
5 changed files with 104 additions and 25 deletions
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2
kernel/rcutree_plugin.h
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@@ -70,6 +70,8 @@ static void __init rcu_bootup_announce_oddness(void)
#if NUM_RCU_LVL_4 != 0
printk(KERN_INFO "\tExperimental four-level hierarchy is enabled.\n");
#endif
if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
}
#ifdef CONFIG_TREE_PREEMPT_RCU