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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-08-20 00:35:53 -0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-11-16 13:05:56 -0500
commit3fbfbf7a3b66ec424042d909f14ba2ddf4372ea8 (patch)
treecc364c320a6e23927ecc154a8ef8021dc7d1a9e8 /include/trace
parentaac1cda34b84a9411d6b8d18c3658f094c834911 (diff)
rcu: Add callback-free CPUs
RCU callback execution can add significant OS jitter and also can degrade both scheduling latency and, in asymmetric multiprocessors, energy efficiency. This commit therefore adds the ability for selected CPUs ("rcu_nocbs=" boot parameter) to have their callbacks offloaded to kthreads. If the "rcu_nocb_poll" boot parameter is also specified, these kthreads will do polling, removing the need for the offloaded CPUs to do wakeups. At least one CPU must be doing normal callback processing: currently CPU 0 cannot be selected as a no-CBs CPU. In addition, attempts to offline the last normal-CBs CPU will fail. This feature was inspired by Jim Houston's and Joe Korty's JRCU, and this commit includes fixes to problems located by Fengguang Wu's kbuild test robot. [ paulmck: Added gfp.h include file as suggested by Fengguang Wu. ] Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/trace')
-rw-r--r--include/trace/events/rcu.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 5bde94d8585b..d4f559b1ec34 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -549,6 +549,7 @@ TRACE_EVENT(rcu_torture_read,
549 * "EarlyExit": rcu_barrier_callback() piggybacked, thus early exit. 549 * "EarlyExit": rcu_barrier_callback() piggybacked, thus early exit.
550 * "Inc1": rcu_barrier_callback() piggyback check counter incremented. 550 * "Inc1": rcu_barrier_callback() piggyback check counter incremented.
551 * "Offline": rcu_barrier_callback() found offline CPU 551 * "Offline": rcu_barrier_callback() found offline CPU
552 * "OnlineNoCB": rcu_barrier_callback() found online no-CBs CPU.
552 * "OnlineQ": rcu_barrier_callback() found online CPU with callbacks. 553 * "OnlineQ": rcu_barrier_callback() found online CPU with callbacks.
553 * "OnlineNQ": rcu_barrier_callback() found online CPU, no callbacks. 554 * "OnlineNQ": rcu_barrier_callback() found online CPU, no callbacks.
554 * "IRQ": An rcu_barrier_callback() callback posted on remote CPU. 555 * "IRQ": An rcu_barrier_callback() callback posted on remote CPU.