* [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() for RCU_NOCB_CPU_ALL
2013-11-18 22:02 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Paul E. McKenney
@ 2013-11-18 22:02 ` Paul E. McKenney
2013-11-18 22:02 ` [PATCH tip/core/rcu 3/3] Optimize RCU_FAST_NO_HZ " Paul E. McKenney
1 sibling, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2013-11-18 22:02 UTC (permalink / raw)
To: linux-kernel
Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, niv, tglx,
peterz, rostedt, dhowells, edumazet, darren, fweisbec, sbw,
Paul E. McKenney
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_needs_cpu() will always
return false, however, the current version nevertheless checks
for RCU callbacks. This commit therefore creates a static inline
implementation of rcu_needs_cpu() that unconditionally returns false
when CONFIG_RCU_NOCB_CPU_ALL=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/linux/rcupdate.h | 9 +++++++++
include/linux/rcutiny.h | 6 ------
include/linux/rcutree.h | 2 ++
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree_plugin.h | 4 ++++
5 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 277d3697f2f3..e6331a6843c4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1027,6 +1027,15 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
#define kfree_rcu(ptr, rcu_head) \
__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
+#if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
+
+static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+{
+ *delta_jiffies = ULONG_MAX;
+ return 0;
+}
+#endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */
+
#ifdef CONFIG_RCU_NOCB_CPU
#ifdef CONFIG_RCU_NOCB_CPU_ALL
static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 6f01771b571c..9524903487d0 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -68,12 +68,6 @@ static inline void kfree_call_rcu(struct rcu_head *head,
call_rcu(head, func);
}
-static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
-{
- *delta_jiffies = ULONG_MAX;
- return 0;
-}
-
static inline void rcu_note_context_switch(int cpu)
{
rcu_sched_qs(cpu);
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 72137ee8c603..81198c84e268 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -31,7 +31,9 @@
#define __LINUX_RCUTREE_H
void rcu_note_context_switch(int cpu);
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
void rcu_cpu_stall_reset(void);
/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7be5efd62fe5..ecca289351e0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2851,7 +2851,7 @@ static int rcu_pending(int cpu)
* non-NULL, store an indication of whether all callbacks are lazy.
* (If there are no callbacks, all of them are deemed to be lazy.)
*/
-static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
+static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
{
bool al = true;
bool hc = false;
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 5e7305b40a27..57d98aa2bd21 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1575,11 +1575,13 @@ static void rcu_prepare_kthreads(int cpu)
* Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs
* any flavor of RCU.
*/
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
{
*delta_jiffies = ULONG_MAX;
return rcu_cpu_has_callbacks(cpu, NULL);
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
/*
* Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
@@ -1685,6 +1687,7 @@ static bool rcu_try_advance_all_cbs(void)
*
* The caller must have disabled interrupts.
*/
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
int rcu_needs_cpu(int cpu, unsigned long *dj)
{
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
@@ -1715,6 +1718,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
}
return 0;
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
/*
* Prepare a CPU for idle from an RCU perspective. The first major task
--
1.8.1.5
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH tip/core/rcu 3/3] Optimize RCU_FAST_NO_HZ for RCU_NOCB_CPU_ALL
2013-11-18 22:02 ` [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Paul E. McKenney
2013-11-18 22:02 ` [PATCH tip/core/rcu 2/3] rcu: Optimize rcu_needs_cpu() " Paul E. McKenney
@ 2013-11-18 22:02 ` Paul E. McKenney
1 sibling, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2013-11-18 22:02 UTC (permalink / raw)
To: linux-kernel
Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, niv, tglx,
peterz, rostedt, dhowells, edumazet, darren, fweisbec, sbw,
Paul E. McKenney
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
If CONFIG_RCU_NOCB_CPU_ALL=y, then no CPU will ever have RCU callbacks
because these callbacks will instead be handled by the rcuo kthreads.
However, the current version of RCU_FAST_NO_HZ nevertheless checks for RCU
callbacks. This commit therefore creates static inline implementations
of rcu_prepare_for_idle() and rcu_cleanup_after_idle() that are no-ops
when CONFIG_RCU_NOCB_CPU_ALL=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree_plugin.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 57d98aa2bd21..d87493bf66e3 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1647,7 +1647,7 @@ extern int tick_nohz_enabled;
* only if it has been awhile since the last time we did so. Afterwards,
* if there are any callbacks ready for immediate invocation, return true.
*/
-static bool rcu_try_advance_all_cbs(void)
+static bool __maybe_unused rcu_try_advance_all_cbs(void)
{
bool cbs_ready = false;
struct rcu_data *rdp;
@@ -1732,6 +1732,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
*/
static void rcu_prepare_for_idle(int cpu)
{
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
struct rcu_data *rdp;
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
struct rcu_node *rnp;
@@ -1782,6 +1783,7 @@ static void rcu_prepare_for_idle(int cpu)
rcu_accelerate_cbs(rsp, rnp, rdp);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
}
/*
@@ -1791,11 +1793,12 @@ static void rcu_prepare_for_idle(int cpu)
*/
static void rcu_cleanup_after_idle(int cpu)
{
-
+#ifndef CONFIG_RCU_NOCB_CPU_ALL
if (rcu_is_nocb_cpu(cpu))
return;
if (rcu_try_advance_all_cbs())
invoke_rcu_core();
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
}
/*
--
1.8.1.5
^ permalink raw reply related [flat|nested] 4+ messages in thread