From f7c9a9b664fb32a127e8e9a987b52023b92c3a0b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 1 Apr 2019 09:57:01 -0700 Subject: rcu/nocb: Rename and document no-CB CB kthread sleep trace event The nocb_cb_wait() function traces a "FollowerSleep" trace_rcu_nocb_wake() event, which never was documented and is now misleading. This commit therefore changes "FollowerSleep" to "CBSleep", documents this, and updates the documentation for "Sleep" as well. Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/trace') diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 02a3f78f7cd8..313324d1b135 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -267,7 +267,8 @@ TRACE_EVENT_RCU(rcu_exp_funnel_lock, * "WakeNotPoll": Don't wake rcuo kthread because it is polling. * "DeferredWake": Carried out the "IsDeferred" wakeup. * "Poll": Start of new polling cycle for rcu_nocb_poll. - * "Sleep": Sleep waiting for CBs for !rcu_nocb_poll. + * "Sleep": Sleep waiting for GP for !rcu_nocb_poll. + * "CBSleep": Sleep waiting for CBs for !rcu_nocb_poll. * "WokeEmpty": rcuo kthread woke to find empty list. * "WokeNonEmpty": rcuo kthread woke to find non-empty list. * "WaitQueue": Enqueue partially done, timed wait for it to complete. -- cgit v1.2.3 From 5d6742b37727e111f4755155e59c5319cf5caa7b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 15 May 2019 09:56:40 -0700 Subject: rcu/nocb: Use rcu_segcblist for no-CBs CPUs Currently the RCU callbacks for no-CBs CPUs are queued on a series of ad-hoc linked lists, which means that these callbacks cannot benefit from "drive-by" grace periods, thus suffering needless delays prior to invocation. In addition, the no-CBs grace-period kthreads first wait for callbacks to appear and later wait for a new grace period, which means that callbacks appearing during a grace-period wait can be delayed. These delays increase memory footprint, and could even result in an out-of-memory condition. This commit therefore enqueues RCU callbacks from no-CBs CPUs on the rcu_segcblist structure that is already used by non-no-CBs CPUs. It also restructures the no-CBs grace-period kthread to be checking for incoming callbacks while waiting for grace periods. Also, instead of waiting for a new grace period, it waits for the closest grace period that will cause some of the callbacks to be safe to invoke. All of these changes reduce callback latency and thus the number of outstanding callbacks, in turn reducing the probability of an out-of-memory condition. Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/trace') diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 313324d1b135..694bd040cf51 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -100,7 +100,6 @@ TRACE_EVENT_RCU(rcu_grace_period, * "Startedroot": Requested a nocb grace period based on root-node data. * "NoGPkthread": The RCU grace-period kthread has not yet started. * "StartWait": Start waiting for the requested grace period. - * "ResumeWait": Resume waiting after signal. * "EndWait": Complete wait. * "Cleanup": Clean up rcu_node structure after previous GP. * "CleanupMore": Clean up, and another GP is needed. -- cgit v1.2.3