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nohz: Optimize full dynticks state checks with static keys 

These APIs are frequenctly accessed and priority is given
to optimize the full dynticks off-case in order to let
distros enable this feature without suffering from
significant performance regressions.

Let's inline these APIs and optimize them with static keys.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
This commit is contained in:
Frederic Weisbecker 2013-07-24 23:52:27 +02:00
parent 73867dcd07
commit 460775df46
2 changed files with 25 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
include/linux/tick.h
View File

@ -10,6 +10,8 @@
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/context_tracking_state.h>
#include <linux/cpumask.h>
#ifdef CONFIG_GENERIC_CLOCKEVENTS
@ -158,15 +160,34 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
# endif /* !CONFIG_NO_HZ_COMMON */
#ifdef CONFIG_NO_HZ_FULL
extern bool tick_nohz_full_running;
extern cpumask_var_t tick_nohz_full_mask;
static inline bool tick_nohz_full_enabled(void)
{
if (!static_key_false(&context_tracking_enabled))
return false;
return tick_nohz_full_running;
}
static inline bool tick_nohz_full_cpu(int cpu)
{
if (!tick_nohz_full_enabled())
return false;
return cpumask_test_cpu(cpu, tick_nohz_full_mask);
}
extern void tick_nohz_init(void);
extern int tick_nohz_full_cpu(int cpu);
extern void tick_nohz_full_check(void);
extern void tick_nohz_full_kick(void);
extern void tick_nohz_full_kick_all(void);
extern void tick_nohz_task_switch(struct task_struct *tsk);
#else
static inline void tick_nohz_init(void) { }
static inline int tick_nohz_full_cpu(int cpu) { return 0; }
static inline bool tick_nohz_full_enabled(void) { return false; }
static inline bool tick_nohz_full_cpu(int cpu) { return false; }
static inline void tick_nohz_full_check(void) { }
static inline void tick_nohz_full_kick(void) { }
static inline void tick_nohz_full_kick_all(void) { }

14
kernel/time/tick-sched.c
View File

@ -149,7 +149,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
}
#ifdef CONFIG_NO_HZ_FULL
static cpumask_var_t tick_nohz_full_mask;
cpumask_var_t tick_nohz_full_mask;
bool tick_nohz_full_running;
static bool can_stop_full_tick(void)
@ -270,14 +270,6 @@ void tick_nohz_task_switch(struct task_struct *tsk)
local_irq_restore(flags);
}
int tick_nohz_full_cpu(int cpu)
{
if (!tick_nohz_full_running)
return 0;
return cpumask_test_cpu(cpu, tick_nohz_full_mask);
}
/* Parse the boot-time nohz CPU list from the kernel parameters. */
static int __init tick_nohz_full_setup(char *str)
{
@ -359,8 +351,6 @@ void __init tick_nohz_init(void)
cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask);
pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
}
#else
#define tick_nohz_full_running (0)
#endif
/*
@ -738,7 +728,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
return false;
}
if (tick_nohz_full_running) {
if (tick_nohz_full_enabled()) {
/*
* Keep the tick alive to guarantee timekeeping progression
* if there are full dynticks CPUs around