android_kernel_oneplus_msm8998/include/linux/timer.h
Joonwoo Park 646bf5125d timer: make deferrable cpu unbound timers really not bound to a cpu
When a deferrable work (INIT_DEFERRABLE_WORK, etc.) is queued via
queue_delayed_work() it's probably intended to run the work item on any
CPU that isn't idle. However, we queue the work to run at a later time
by starting a deferrable timer that binds to whatever CPU the work is
queued on which is same with queue_delayed_work_on(smp_processor_id())
effectively.

As a result WORK_CPU_UNBOUND work items aren't really cpu unbound now.
In fact this is perfectly fine with UP kernel and also won't affect much a
system without dyntick with SMP kernel too as every cpus run timers
periodically.  But on SMP systems with dyntick current implementation leads
deferrable timers not very scalable because the timer's base which has
queued the deferrable timer won't wake up till next non-deferrable timer
expires even though there are possible other non idle cpus are running
which are able to run expired deferrable timers.

The deferrable work is a good example of the current implementation's
victim like below.

INIT_DEFERRABLE_WORK(&dwork, fn);
CPU 0                                 CPU 1
queue_delayed_work(wq, &dwork, HZ);
    queue_delayed_work_on(WORK_CPU_UNBOUND);
        ...
	__mod_timer() -> queues timer to the
			 current cpu's timer
			 base.
	...
tick_nohz_idle_enter() -> cpu enters idle.
A second later
cpu 0 is now in idle.                 cpu 1 exits idle or wasn't in idle so
                                      now it's in active but won't
cpu 0 won't wake up till next         handle cpu unbound deferrable timer
non-deferrable timer expires.         as it's in cpu 0's timer base.

To make all cpu unbound deferrable timers are scalable, introduce a common
timer base which is only for cpu unbound deferrable timers to make those
are indeed cpu unbound so that can be scheduled by tick_do_timer_cpu.
This common timer fixes scalability issue of delayed work and all other cpu
unbound deferrable timer using implementations.

Change-Id: I8b6c57d8b6445a76fa02a8cb598a8ef22aef7200
CC: Thomas Gleixner <tglx@linutronix.de>
CC: John Stultz <john.stultz@linaro.org>
CC: Tejun Heo <tj@kernel.org>
[joonwoop@codeaurora.org: timer->base replaced with CPU index so get
 the deferrable timer wheel from lock_timer_base() instead of
 do_init_timer().]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
2016-03-23 21:10:48 -07:00

263 lines
7.8 KiB
C

#ifndef _LINUX_TIMER_H
#define _LINUX_TIMER_H
#include <linux/list.h>
#include <linux/ktime.h>
#include <linux/stddef.h>
#include <linux/debugobjects.h>
#include <linux/stringify.h>
struct tvec_base;
struct timer_list {
/*
* All fields that change during normal runtime grouped to the
* same cacheline
*/
struct hlist_node entry;
unsigned long expires;
void (*function)(unsigned long);
unsigned long data;
u32 flags;
int slack;
#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
char start_comm[16];
#endif
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};
#ifdef CONFIG_LOCKDEP
/*
* NB: because we have to copy the lockdep_map, setting the lockdep_map key
* (second argument) here is required, otherwise it could be initialised to
* the copy of the lockdep_map later! We use the pointer to and the string
* "<file>:<line>" as the key resp. the name of the lockdep_map.
*/
#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn) \
.lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
#else
#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
#endif
/*
* A deferrable timer will work normally when the system is busy, but
* will not cause a CPU to come out of idle just to service it; instead,
* the timer will be serviced when the CPU eventually wakes up with a
* subsequent non-deferrable timer.
*
* An irqsafe timer is executed with IRQ disabled and it's safe to wait for
* the completion of the running instance from IRQ handlers, for example,
* by calling del_timer_sync().
*
* Note: The irq disabled callback execution is a special case for
* workqueue locking issues. It's not meant for executing random crap
* with interrupts disabled. Abuse is monitored!
*/
#define TIMER_CPUMASK 0x0007FFFF
#define TIMER_MIGRATING 0x00080000
#define TIMER_BASEMASK (TIMER_CPUMASK | TIMER_MIGRATING)
#define TIMER_DEFERRABLE 0x00100000
#define TIMER_IRQSAFE 0x00200000
#define TIMER_PINNED_ON_CPU 0x00400000
#define __TIMER_INITIALIZER(_function, _expires, _data, _flags) { \
.entry = { .next = TIMER_ENTRY_STATIC }, \
.function = (_function), \
.expires = (_expires), \
.data = (_data), \
.flags = (_flags), \
.slack = -1, \
__TIMER_LOCKDEP_MAP_INITIALIZER( \
__FILE__ ":" __stringify(__LINE__)) \
}
#define TIMER_INITIALIZER(_function, _expires, _data) \
__TIMER_INITIALIZER((_function), (_expires), (_data), 0)
#define TIMER_DEFERRED_INITIALIZER(_function, _expires, _data) \
__TIMER_INITIALIZER((_function), (_expires), (_data), TIMER_DEFERRABLE)
#define DEFINE_TIMER(_name, _function, _expires, _data) \
struct timer_list _name = \
TIMER_INITIALIZER(_function, _expires, _data)
void init_timer_key(struct timer_list *timer, unsigned int flags,
const char *name, struct lock_class_key *key);
#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
extern void init_timer_on_stack_key(struct timer_list *timer,
unsigned int flags, const char *name,
struct lock_class_key *key);
extern void destroy_timer_on_stack(struct timer_list *timer);
#else
static inline void destroy_timer_on_stack(struct timer_list *timer) { }
static inline void init_timer_on_stack_key(struct timer_list *timer,
unsigned int flags, const char *name,
struct lock_class_key *key)
{
init_timer_key(timer, flags, name, key);
}
#endif
#ifdef CONFIG_LOCKDEP
#define __init_timer(_timer, _flags) \
do { \
static struct lock_class_key __key; \
init_timer_key((_timer), (_flags), #_timer, &__key); \
} while (0)
#define __init_timer_on_stack(_timer, _flags) \
do { \
static struct lock_class_key __key; \
init_timer_on_stack_key((_timer), (_flags), #_timer, &__key); \
} while (0)
#else
#define __init_timer(_timer, _flags) \
init_timer_key((_timer), (_flags), NULL, NULL)
#define __init_timer_on_stack(_timer, _flags) \
init_timer_on_stack_key((_timer), (_flags), NULL, NULL)
#endif
#define init_timer(timer) \
__init_timer((timer), 0)
#define init_timer_deferrable(timer) \
__init_timer((timer), TIMER_DEFERRABLE)
#define init_timer_on_stack(timer) \
__init_timer_on_stack((timer), 0)
#define __setup_timer(_timer, _fn, _data, _flags) \
do { \
__init_timer((_timer), (_flags)); \
(_timer)->function = (_fn); \
(_timer)->data = (_data); \
} while (0)
#define __setup_timer_on_stack(_timer, _fn, _data, _flags) \
do { \
__init_timer_on_stack((_timer), (_flags)); \
(_timer)->function = (_fn); \
(_timer)->data = (_data); \
} while (0)
#define setup_timer(timer, fn, data) \
__setup_timer((timer), (fn), (data), 0)
#define setup_timer_on_stack(timer, fn, data) \
__setup_timer_on_stack((timer), (fn), (data), 0)
#define setup_deferrable_timer_on_stack(timer, fn, data) \
__setup_timer_on_stack((timer), (fn), (data), TIMER_DEFERRABLE)
/**
* timer_pending - is a timer pending?
* @timer: the timer in question
*
* timer_pending will tell whether a given timer is currently pending,
* or not. Callers must ensure serialization wrt. other operations done
* to this timer, eg. interrupt contexts, or other CPUs on SMP.
*
* return value: 1 if the timer is pending, 0 if not.
*/
static inline int timer_pending(const struct timer_list * timer)
{
return timer->entry.pprev != NULL;
}
extern void add_timer_on(struct timer_list *timer, int cpu);
extern int del_timer(struct timer_list * timer);
extern int mod_timer(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pinned(struct timer_list *timer, unsigned long expires);
extern void set_timer_slack(struct timer_list *time, int slack_hz);
#define TIMER_NOT_PINNED 0
#define TIMER_PINNED 1
/*
* The jiffies value which is added to now, when there is no timer
* in the timer wheel:
*/
#define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1)
/*
* Timer-statistics info:
*/
#ifdef CONFIG_TIMER_STATS
extern int timer_stats_active;
extern void init_timer_stats(void);
extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
void *timerf, char *comm, u32 flags);
extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
void *addr);
static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
{
if (likely(!timer_stats_active))
return;
__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
}
static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
{
timer->start_site = NULL;
}
#else
static inline void init_timer_stats(void)
{
}
static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
{
}
static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
{
}
#endif
extern void add_timer(struct timer_list *timer);
extern int try_to_del_timer_sync(struct timer_list *timer);
#ifdef CONFIG_SMP
extern int del_timer_sync(struct timer_list *timer);
#else
# define del_timer_sync(t) del_timer(t)
#endif
#define del_singleshot_timer_sync(t) del_timer_sync(t)
extern void init_timers(void);
extern void run_local_timers(void);
struct hrtimer;
extern enum hrtimer_restart it_real_fn(struct hrtimer *);
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
#include <linux/sysctl.h>
extern struct tvec_base tvec_base_deferrable;
extern unsigned int sysctl_timer_migration;
int timer_migration_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
#endif
unsigned long __round_jiffies(unsigned long j, int cpu);
unsigned long __round_jiffies_relative(unsigned long j, int cpu);
unsigned long round_jiffies(unsigned long j);
unsigned long round_jiffies_relative(unsigned long j);
unsigned long __round_jiffies_up(unsigned long j, int cpu);
unsigned long __round_jiffies_up_relative(unsigned long j, int cpu);
unsigned long round_jiffies_up(unsigned long j);
unsigned long round_jiffies_up_relative(unsigned long j);
#endif