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authorEric Dumazet <eric.dumazet@gmail.com>2011-04-28 07:23:45 +0200
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-05-05 23:16:59 -0700
commitb554d7de8d112fca4188da3bf0d7f8b56f42fb95 (patch)
tree3641a25b7356da1bdcb52f6ff160f605ed778cd4
parent2655d57ef35aa327a2e58a1c5dc7b65c65003f4e (diff)
rcu: optimize rcutiny
rcu_sched_qs() currently calls local_irq_save()/local_irq_restore() up to three times. Remove irq masking from rcu_qsctr_help() / invoke_rcu_kthread() and do it once in rcu_sched_qs() / rcu_bh_qs() This generates smaller code as well. text data bss dec hex filename 2314 156 24 2494 9be kernel/rcutiny.old.o 2250 156 24 2430 97e kernel/rcutiny.new.o Fix an outdated comment for rcu_qsctr_help() Move invoke_rcu_kthread() definition before its use. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
-rw-r--r--kernel/rcutiny.c43
1 files changed, 21 insertions, 22 deletions
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 4d60fbc9c64c..421abfd3641d 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -40,10 +40,10 @@
static struct task_struct *rcu_kthread_task;
static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
static unsigned long have_rcu_kthread_work;
-static void invoke_rcu_kthread(void);
/* Forward declarations for rcutiny_plugin.h. */
struct rcu_ctrlblk;
+static void invoke_rcu_kthread(void);
static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
static int rcu_kthread(void *arg);
static void __call_rcu(struct rcu_head *head,
@@ -79,36 +79,45 @@ void rcu_exit_nohz(void)
#endif /* #ifdef CONFIG_NO_HZ */
/*
- * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
- * Also disable irqs to avoid confusion due to interrupt handlers
+ * Helper function for rcu_sched_qs() and rcu_bh_qs().
+ * Also irqs are disabled to avoid confusion due to interrupt handlers
* invoking call_rcu().
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
- unsigned long flags;
-
- local_irq_save(flags);
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
- local_irq_restore(flags);
return 1;
}
- local_irq_restore(flags);
return 0;
}
/*
+ * Wake up rcu_kthread() to process callbacks now eligible for invocation
+ * or to boost readers.
+ */
+static void invoke_rcu_kthread(void)
+{
+ have_rcu_kthread_work = 1;
+ wake_up(&rcu_kthread_wq);
+}
+
+/*
* Record an rcu quiescent state. And an rcu_bh quiescent state while we
* are at it, given that any rcu quiescent state is also an rcu_bh
* quiescent state. Use "+" instead of "||" to defeat short circuiting.
*/
void rcu_sched_qs(int cpu)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
rcu_qsctr_help(&rcu_bh_ctrlblk))
invoke_rcu_kthread();
+ local_irq_restore(flags);
}
/*
@@ -116,8 +125,12 @@ void rcu_sched_qs(int cpu)
*/
void rcu_bh_qs(int cpu)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
invoke_rcu_kthread();
+ local_irq_restore(flags);
}
/*
@@ -208,20 +221,6 @@ static int rcu_kthread(void *arg)
}
/*
- * Wake up rcu_kthread() to process callbacks now eligible for invocation
- * or to boost readers.
- */
-static void invoke_rcu_kthread(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- have_rcu_kthread_work = 1;
- wake_up(&rcu_kthread_wq);
- local_irq_restore(flags);
-}
-
-/*
* Wait for a grace period to elapse. But it is illegal to invoke
* synchronize_sched() from within an RCU read-side critical section.
* Therefore, any legal call to synchronize_sched() is a quiescent