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Date: Wed, 9 Dec 2015 15:03:08 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
bobby.prani@...il.com,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH v2 tip/core/rcu 11/11] rcu: Remove TINY_RCU bloat from pointless boot parameters
The rcu_expedited, rcu_normal, and rcu_normal_after_boot kernel boot
parameters are pointless in the case of TINY_RCU because in that case
synchronous grace periods, both expedited and normal, are no-ops.
However, these three symbols contribute several hundred bytes of bloat.
This commit therefore uses CPP directives to avoid compiling this code
in TINY_RCU kernels.
Reported-by: kbuild test robot <fengguang.wu@...el.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@...htriplett.org>
---
Documentation/kernel-parameters.txt | 13 ++++++++-----
include/linux/rcupdate.h | 9 ++++++++-
kernel/ksysfs.c | 4 ++++
kernel/rcu/update.c | 7 ++++---
4 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 197305bbb9b7..d8186da15ca1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3308,20 +3308,23 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
of synchronize_rcu(). This reduces latency,
but can increase CPU utilization, degrade
real-time latency, and degrade energy efficiency.
+ No effect on CONFIG_TINY_RCU kernels.
rcupdate.rcu_normal= [KNL]
Use only normal grace-period primitives,
for example, synchronize_rcu() instead of
synchronize_rcu_expedited(). This improves
- real-time latency, CPU utilization, and energy
- efficiency, but can expose users to increased
- grace-period latency. This parameter overrides
- rcupdate.rcu_expedited.
+ real-time latency, CPU utilization, and
+ energy efficiency, but can expose users to
+ increased grace-period latency. This parameter
+ overrides rcupdate.rcu_expedited. No effect on
+ CONFIG_TINY_RCU kernels.
rcupdate.rcu_normal_after_boot= [KNL]
Once boot has completed (that is, after
rcu_end_inkernel_boot() has been invoked), use
- only normal grace-period primitives.
+ only normal grace-period primitives. No effect
+ on CONFIG_TINY_RCU kernels.
rcupdate.rcu_task_stall_timeout= [KNL]
Set timeout in jiffies for RCU task stall warning
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 98d9f30c02d4..47e95b80bebd 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -48,8 +48,10 @@
#include <asm/barrier.h>
+#ifndef CONFIG_TINY_RCU
extern int rcu_expedited; /* for sysctl */
extern int rcu_normal; /* also for sysctl */
+#endif /* #ifndef CONFIG_TINY_RCU */
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
@@ -327,7 +329,6 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
void rcu_init(void);
-void rcu_end_inkernel_boot(void);
void rcu_sched_qs(void);
void rcu_bh_qs(void);
void rcu_check_callbacks(int user);
@@ -335,6 +336,12 @@ struct notifier_block;
int rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu);
+#ifndef CONFIG_TINY_RCU
+void rcu_end_inkernel_boot(void);
+#else /* #ifndef CONFIG_TINY_RCU */
+static inline void rcu_end_inkernel_boot(void) { }
+#endif /* #ifndef CONFIG_TINY_RCU */
+
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);
void rcu_sysrq_end(void);
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index b4e2fa52d8bc..152da4a48867 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -144,6 +144,7 @@ static ssize_t fscaps_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(fscaps);
+#ifndef CONFIG_TINY_RCU
int rcu_expedited;
static ssize_t rcu_expedited_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
@@ -177,6 +178,7 @@ static ssize_t rcu_normal_store(struct kobject *kobj,
return count;
}
KERNEL_ATTR_RW(rcu_normal);
+#endif /* #ifndef CONFIG_TINY_RCU */
/*
* Make /sys/kernel/notes give the raw contents of our kernel .notes section.
@@ -219,8 +221,10 @@ static struct attribute * kernel_attrs[] = {
&kexec_crash_size_attr.attr,
&vmcoreinfo_attr.attr,
#endif
+#ifndef CONFIG_TINY_RCU
&rcu_expedited_attr.attr,
&rcu_normal_attr.attr,
+#endif
NULL
};
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 12b91f5a60a6..76b94e19430b 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -60,11 +60,12 @@ MODULE_ALIAS("rcupdate");
#endif
#define MODULE_PARAM_PREFIX "rcupdate."
+#ifndef CONFIG_TINY_RCU
module_param(rcu_expedited, int, 0);
module_param(rcu_normal, int, 0);
-
static int rcu_normal_after_boot;
module_param(rcu_normal_after_boot, int, 0);
+#endif /* #ifndef CONFIG_TINY_RCU */
#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
/**
@@ -172,8 +173,6 @@ void rcu_unexpedite_gp(void)
}
EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
-#endif /* #ifndef CONFIG_TINY_RCU */
-
/*
* Inform RCU of the end of the in-kernel boot sequence.
*/
@@ -185,6 +184,8 @@ void rcu_end_inkernel_boot(void)
WRITE_ONCE(rcu_normal, 1);
}
+#endif /* #ifndef CONFIG_TINY_RCU */
+
#ifdef CONFIG_PREEMPT_RCU
/*
--
2.5.2
--
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