rcu: Make rcu_nocb_wait_gp() check if GP already requested

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This commit makes rcu_nocb_wait_gp() check rdp->gp_seq_needed to see
if the current CPU already knows about the needed grace period having
already been requested.  If so, it avoids acquiring the corresponding
leaf rcu_node structure's ->lock, thus decreasing contention.  This
optimization is intended for cases where either multiple leader rcuo
kthreads are running on the same CPU or these kthreads are running on
a non-offloaded (e.g., housekeeping) CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Move lock release past "if" as suggested by Joel Fernandes. ]
[ paulmck: Fix caching of furthest-future requested grace period. ]

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This commit is contained in:

Paul E. McKenney 2018-05-01 11:07:23 -07:00

parent 7a1d0f23ad

commit ab5e869c1f

2 changed files with 15 additions and 5 deletions

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5

kernel/rcu/tree.c

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15

kernel/rcu/tree_plugin.h

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