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| author | Joel Fernandes (Google) <joel@joelfernandes.org> | 2020-11-14 14:31:32 -0500 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-01-06 16:24:19 -0800 |
| commit | 3afe7fa535491ecd0382c3968dc2349602bff8a2 (patch) | |
| tree | fc03859921463287aa6c086ddc78635d05ab7da6 /kernel | |
| parent | 68804cf1c905ce227e4e1d0bc252c216811c59fd (diff) | |
| download | linux-stable-3afe7fa535491ecd0382c3968dc2349602bff8a2.tar.gz linux-stable-3afe7fa535491ecd0382c3968dc2349602bff8a2.tar.bz2 linux-stable-3afe7fa535491ecd0382c3968dc2349602bff8a2.zip | |
rcu/trace: Add tracing for how segcb list changes
This commit adds tracing to track how the segcb list changes before/after
acceleration, during queuing and during dequeuing.
This tracing helped discover an optimization that avoided needless GP
requests when no callbacks were accelerated. The tracing overhead is
minimal as each segment's length is now stored in the respective segment.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b0fb654cba80..6bf269c91393 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1495,6 +1495,8 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp) if (!rcu_segcblist_pend_cbs(&rdp->cblist)) return false; + trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPreAcc")); + /* * Callbacks are often registered with incomplete grace-period * information. Something about the fact that getting exact @@ -1515,6 +1517,8 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp) else trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB")); + trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPostAcc")); + return ret; } @@ -2471,11 +2475,14 @@ static void rcu_do_batch(struct rcu_data *rdp) rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); if (offloaded) rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); + + trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued")); rcu_nocb_unlock_irqrestore(rdp, flags); /* Invoke callbacks. */ tick_dep_set_task(current, TICK_DEP_BIT_RCU); rhp = rcu_cblist_dequeue(&rcl); + for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { rcu_callback_t f; @@ -2987,6 +2994,8 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) trace_rcu_callback(rcu_state.name, head, rcu_segcblist_n_cbs(&rdp->cblist)); + trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCBQueued")); + /* Go handle any RCU core processing required. */ if (unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) { __call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */ |