[tip:timers/core] timer: Use hlist for the timer wheel hash buckets

From: tip-bot for Thomas Gleixner
Date: Fri Jun 19 2015 - 09:39:11 EST

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Commit-ID: 1dabbcec2c0a36fe43509d06499b9e512e70a028
Gitweb: http://git.kernel.org/tip/1dabbcec2c0a36fe43509d06499b9e512e70a028
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 26 May 2015 22:50:28 +0000
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 19 Jun 2015 15:18:27 +0200

timer: Use hlist for the timer wheel hash buckets

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@xxxxxxxxxxxxx>
Reviewed-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Joonwoo Park <joonwoop@xxxxxxxxxxxxxx>
Cc: Wenbo Wang <wenbo.wang@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150526224511.854731214@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
include/linux/timer.h | 6 ++---
kernel/time/timer.c | 64 ++++++++++++++++++++++-----------------------------
2 files changed, 30 insertions(+), 40 deletions(-)

diff --git a/include/linux/timer.h b/include/linux/timer.h
index fbb80e0..064ee24 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -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;

@@ -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), \
@@ -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);
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index e212df2..3a5e0c8 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -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 {
@@ -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;
@@ -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)
@@ -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;
@@ -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
@@ -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
@@ -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
@@ -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);
@@ -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) {
@@ -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);
@@ -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;

@@ -1271,7 +1272,7 @@ cascade:

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;

@@ -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);
@@ -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;
}
--
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