diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2022-08-05 15:42:25 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-08-31 05:09:22 -0700 |
| commit | d761de8a7dcef8e8e9e20a543f85a2c079ae3d0d (patch) | |
| tree | e2016c6787384500b8f3520c78782dbc3d5b6230 /kernel/rcu | |
| parent | b3cdd0a79c875d5e9cac9f6555485031ce5bea81 (diff) | |
rcu: Make synchronize_rcu() fastpath update only boot-CPU counters
Large systems can have hundreds of rcu_node structures, and updating
counters in each of them might slow down booting. This commit therefore
updates only the counters in those rcu_node structures corresponding
to the boot CPU, up to and including the root rcu_node structure.
The counters for the remaining rcu_node structures are updated by the
rcu_scheduler_starting() function, which executes just before the first
non-boot kthread is spawned.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b9e8ed00536d..ef15bae3c7c7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3504,11 +3504,14 @@ void synchronize_rcu(void) rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_snap); rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_snap); - // Update normal grace-period counters to record grace period. + // Update the normal grace-period counters to record + // this grace period, but only those used by the boot CPU. + // The rcu_scheduler_starting() will take care of the rest of + // these counters. local_irq_save(flags); WARN_ON_ONCE(num_online_cpus() > 1); rcu_state.gp_seq += (1 << RCU_SEQ_CTR_SHIFT); - rcu_for_each_node_breadth_first(rnp) + for (rnp = this_cpu_ptr(&rcu_data)->mynode; rnp; rnp = rnp->parent) rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq; local_irq_restore(flags); } @@ -4456,9 +4459,20 @@ early_initcall(rcu_spawn_gp_kthread); */ void rcu_scheduler_starting(void) { + unsigned long flags; + struct rcu_node *rnp; + WARN_ON(num_online_cpus() != 1); WARN_ON(nr_context_switches() > 0); rcu_test_sync_prims(); + + // Fix up the ->gp_seq counters. + local_irq_save(flags); + rcu_for_each_node_breadth_first(rnp) + rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq; + local_irq_restore(flags); + + // Switch out of early boot mode. rcu_scheduler_active = RCU_SCHEDULER_INIT; rcu_test_sync_prims(); } |