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timer: Use hlist for the timer wheel hash buckets
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This reduces the size of struct tvec_base by 50% and results in
slightly smaller code as well.

Before:
   struct tvec_base: size: 8256, cachelines: 129

   text	   data	    bss	    dec	    hex	filename
  17698	  13297	   8256	  39251	   9953	../build/kernel/time/timer.o

After:
  struct tvec_base: 4160, cachelines: 65

   text	   data	    bss	    dec	    hex	filename
  17491	   9201	   4160	  30852	   7884	../build/kernel/time/timer.o

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224511.854731214@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@KAGA-KOKO
KAGA-KOKO committed Jun 19, 2015
1 parent 1bd04bf commit 1dabbce
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Showing 2 changed files with 30 additions and 40 deletions.
6 changes: 3 additions & 3 deletions include/linux/timer.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ struct timer_list {
* All fields that change during normal runtime grouped to the
* same cacheline
*/
struct list_head entry;
struct hlist_node entry;
unsigned long expires;
struct tvec_base *base;

Expand Down Expand Up @@ -71,7 +71,7 @@ extern struct tvec_base boot_tvec_bases;
#define TIMER_FLAG_MASK 0x3LU

#define __TIMER_INITIALIZER(_function, _expires, _data, _flags) { \
.entry = { .prev = TIMER_ENTRY_STATIC }, \
.entry = { .next = TIMER_ENTRY_STATIC }, \
.function = (_function), \
.expires = (_expires), \
.data = (_data), \
Expand Down Expand Up @@ -168,7 +168,7 @@ static inline void init_timer_on_stack_key(struct timer_list *timer,
*/
static inline int timer_pending(const struct timer_list * timer)
{
return timer->entry.next != NULL;
return timer->entry.pprev != NULL;
}

extern void add_timer_on(struct timer_list *timer, int cpu);
Expand Down
64 changes: 27 additions & 37 deletions kernel/time/timer.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -70,11 +70,11 @@ EXPORT_SYMBOL(jiffies_64);
#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))

struct tvec {
struct list_head vec[TVN_SIZE];
struct hlist_head vec[TVN_SIZE];
};

struct tvec_root {
struct list_head vec[TVR_SIZE];
struct hlist_head vec[TVR_SIZE];
};

struct tvec_base {
Expand Down Expand Up @@ -356,7 +356,7 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
unsigned long expires = timer->expires;
unsigned long idx = expires - base->timer_jiffies;
struct list_head *vec;
struct hlist_head *vec;

if (idx < TVR_SIZE) {
int i = expires & TVR_MASK;
Expand Down Expand Up @@ -390,7 +390,7 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
vec = base->tv5.vec + i;
}

list_add(&timer->entry, vec);
hlist_add_head(&timer->entry, vec);
}

static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
Expand Down Expand Up @@ -504,8 +504,8 @@ static int timer_fixup_activate(void *addr, enum debug_obj_state state)
* statically initialized. We just make sure that it
* is tracked in the object tracker.
*/
if (timer->entry.next == NULL &&
timer->entry.prev == TIMER_ENTRY_STATIC) {
if (timer->entry.pprev == NULL &&
timer->entry.next == TIMER_ENTRY_STATIC) {
debug_object_init(timer, &timer_debug_descr);
debug_object_activate(timer, &timer_debug_descr);
return 0;
Expand Down Expand Up @@ -551,7 +551,7 @@ static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)

switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
if (timer->entry.prev == TIMER_ENTRY_STATIC) {
if (timer->entry.next == TIMER_ENTRY_STATIC) {
/*
* This is not really a fixup. The timer was
* statically initialized. We just make sure that it
Expand Down Expand Up @@ -655,7 +655,7 @@ static void do_init_timer(struct timer_list *timer, unsigned int flags,
{
struct tvec_base *base = raw_cpu_read(tvec_bases);

timer->entry.next = NULL;
timer->entry.pprev = NULL;
timer->base = (void *)((unsigned long)base | flags);
timer->slack = -1;
#ifdef CONFIG_TIMER_STATS
Expand Down Expand Up @@ -687,14 +687,14 @@ EXPORT_SYMBOL(init_timer_key);

static inline void detach_timer(struct timer_list *timer, bool clear_pending)
{
struct list_head *entry = &timer->entry;
struct hlist_node *entry = &timer->entry;

debug_deactivate(timer);

__list_del(entry->prev, entry->next);
__hlist_del(entry);
if (clear_pending)
entry->next = NULL;
entry->prev = LIST_POISON2;
entry->pprev = NULL;
entry->next = LIST_POISON2;
}

static inline void
Expand Down Expand Up @@ -1095,16 +1095,17 @@ EXPORT_SYMBOL(del_timer_sync);
static int cascade(struct tvec_base *base, struct tvec *tv, int index)
{
/* cascade all the timers from tv up one level */
struct timer_list *timer, *tmp;
struct list_head tv_list;
struct timer_list *timer;
struct hlist_node *tmp;
struct hlist_head tv_list;

list_replace_init(tv->vec + index, &tv_list);
hlist_move_list(tv->vec + index, &tv_list);

/*
* We are removing _all_ timers from the list, so we
* don't have to detach them individually.
*/
list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
hlist_for_each_entry_safe(timer, tmp, &tv_list, entry) {
BUG_ON(tbase_get_base(timer->base) != base);
/* No accounting, while moving them */
__internal_add_timer(base, timer);
Expand Down Expand Up @@ -1172,8 +1173,8 @@ static inline void __run_timers(struct tvec_base *base)
spin_lock_irq(&base->lock);

while (time_after_eq(jiffies, base->timer_jiffies)) {
struct list_head work_list;
struct list_head *head = &work_list;
struct hlist_head work_list;
struct hlist_head *head = &work_list;
int index;

if (!base->all_timers) {
Expand All @@ -1192,13 +1193,13 @@ static inline void __run_timers(struct tvec_base *base)
!cascade(base, &base->tv4, INDEX(2)))
cascade(base, &base->tv5, INDEX(3));
++base->timer_jiffies;
list_replace_init(base->tv1.vec + index, head);
while (!list_empty(head)) {
hlist_move_list(base->tv1.vec + index, head);
while (!hlist_empty(head)) {
void (*fn)(unsigned long);
unsigned long data;
bool irqsafe;

timer = list_first_entry(head, struct timer_list,entry);
timer = hlist_entry(head->first, struct timer_list, entry);
fn = timer->function;
data = timer->data;
irqsafe = tbase_get_irqsafe(timer->base);
Expand Down Expand Up @@ -1240,7 +1241,7 @@ static unsigned long __next_timer_interrupt(struct tvec_base *base)
/* Look for timer events in tv1. */
index = slot = timer_jiffies & TVR_MASK;
do {
list_for_each_entry(nte, base->tv1.vec + slot, entry) {
hlist_for_each_entry(nte, base->tv1.vec + slot, entry) {
if (tbase_get_deferrable(nte->base))
continue;

Expand Down Expand Up @@ -1271,7 +1272,7 @@ static unsigned long __next_timer_interrupt(struct tvec_base *base)

index = slot = timer_jiffies & TVN_MASK;
do {
list_for_each_entry(nte, varp->vec + slot, entry) {
hlist_for_each_entry(nte, varp->vec + slot, entry) {
if (tbase_get_deferrable(nte->base))
continue;

Expand Down Expand Up @@ -1530,12 +1531,12 @@ signed long __sched schedule_timeout_uninterruptible(signed long timeout)
EXPORT_SYMBOL(schedule_timeout_uninterruptible);

#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
static void migrate_timer_list(struct tvec_base *new_base, struct hlist_head *head)
{
struct timer_list *timer;

while (!list_empty(head)) {
timer = list_first_entry(head, struct timer_list, entry);
while (!hlist_empty(head)) {
timer = hlist_entry(head->first, struct timer_list, entry);
/* We ignore the accounting on the dying cpu */
detach_timer(timer, false);
timer_set_base(timer, new_base);
Expand Down Expand Up @@ -1603,23 +1604,12 @@ static inline void timer_register_cpu_notifier(void) { }

static void __init init_timer_cpu(struct tvec_base *base, int cpu)
{
int j;

BUG_ON(base != tbase_get_base(base));

base->cpu = cpu;
per_cpu(tvec_bases, cpu) = base;
spin_lock_init(&base->lock);

for (j = 0; j < TVN_SIZE; j++) {
INIT_LIST_HEAD(base->tv5.vec + j);
INIT_LIST_HEAD(base->tv4.vec + j);
INIT_LIST_HEAD(base->tv3.vec + j);
INIT_LIST_HEAD(base->tv2.vec + j);
}
for (j = 0; j < TVR_SIZE; j++)
INIT_LIST_HEAD(base->tv1.vec + j);

base->timer_jiffies = jiffies;
base->next_timer = base->timer_jiffies;
}
Expand Down

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