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| author | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-05-21 22:39:15 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-08-13 23:35:49 +0200 |
| commit | c1ab99d66ebcebedd9d416a840c488eaf079f3e9 (patch) | |
| tree | 5785689b2e0fb75287b792a3d6f6271325b28ba9 /kernel/rcu | |
| parent | rcu/nocb: Use build-time no-CBs check in rcu_do_batch() (diff) | |
| download | linux-c1ab99d66ebcebedd9d416a840c488eaf079f3e9.tar.xz linux-c1ab99d66ebcebedd9d416a840c488eaf079f3e9.zip | |
rcu/nocb: Use build-time no-CBs check in rcu_core()
Currently, rcu_core() invokes rcu_segcblist_is_offloaded() each time it
needs to know whether the current CPU is a no-CBs CPU. Given that it is
not possible to change the no-CBs status of a CPU after boot, and given
that it is not possible to even have no-CBs CPUs in CONFIG_RCU_NOCB_CPU=n
kernels, this repeated runtime invocation wastes CPU. This commit
therefore created a const on-stack variable to allow this check to be
done only once per rcu_core() invocation.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 16dabd6b36d7..14939273d120 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2302,6 +2302,8 @@ static __latent_entropy void rcu_core(void) unsigned long flags; struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); struct rcu_node *rnp = rdp->mynode; + const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); if (cpu_is_offline(smp_processor_id())) return; @@ -2321,8 +2323,7 @@ static __latent_entropy void rcu_core(void) /* No grace period and unregistered callbacks? */ if (!rcu_gp_in_progress() && - rcu_segcblist_is_enabled(&rdp->cblist) && - !rcu_segcblist_is_offloaded(&rdp->cblist)) { + rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) { local_irq_save(flags); if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) rcu_accelerate_cbs_unlocked(rnp, rdp); @@ -2332,8 +2333,7 @@ static __latent_entropy void rcu_core(void) rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check()); /* If there are callbacks ready, invoke them. */ - if (!rcu_segcblist_is_offloaded(&rdp->cblist) && - rcu_segcblist_ready_cbs(&rdp->cblist) && + if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist) && likely(READ_ONCE(rcu_scheduler_fully_active))) rcu_do_batch(rdp); |