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rcu: Segregate rcu_state fields to improve cache locality 

The fields in the rcu_state structure that are protected by the
root rcu_node structure's ->lock can share a cache line with the
fields protected by ->onofflock.  This can result in excessive
memory contention on large systems, so this commit applies
____cacheline_internodealigned_in_smp to the ->onofflock field in
order to segregate them.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Dimitri Sivanich 2012-06-29 14:17:29 -07:00 committed by Paul E. McKenney
parent b626c1b689
commit b402b73b3a
1 changed files with 2 additions and 1 deletions
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3
kernel/rcutree.h
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@ -394,7 +394,8 @@ struct rcu_state {
/* End of fields guarded by root rcu_node's lock. */
raw_spinlock_t onofflock; /* exclude on/offline and */
raw_spinlock_t onofflock ____cacheline_internodealigned_in_smp;
/* exclude on/offline and */
/* starting new GP. */
struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */
/* need a grace period. */