diff --git a/include/linux/timer.h b/include/linux/timer.h
index 989f33d16ebf261317ec7e6c07faa188dee3ee7c..5869ab9848fe1d5870adf3992169754b3e861e77 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -64,6 +64,8 @@ struct timer_list {
#define TIMER_DEFERRABLE 0x00080000
#define TIMER_PINNED 0x00100000
#define TIMER_IRQSAFE 0x00200000
+#define TIMER_ARRAYSHIFT 22
+#define TIMER_ARRAYMASK 0xFFC00000
#define __TIMER_INITIALIZER(_function, _expires, _data, _flags) { \
.entry = { .next = TIMER_ENTRY_STATIC }, \
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index f259a3ef4577c8fc7d65a11e3e6fbf8ed123385b..86e95b72665dcfac8123061df7d53f7e10f1fe50 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -59,43 +59,151 @@ __visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
EXPORT_SYMBOL(jiffies_64);
/*
- * per-CPU timer vector definitions:
+ * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
+ * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
+ * level has a different granularity.
+ *
+ * The level granularity is: LVL_CLK_DIV ^ lvl
+ * The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
+ *
+ * The array level of a newly armed timer depends on the relative expiry
+ * time. The farther the expiry time is away the higher the array level and
+ * therefor the granularity becomes.
+ *
+ * Contrary to the original timer wheel implementation, which aims for 'exact'
+ * expiry of the timers, this implementation removes the need for recascading
+ * the timers into the lower array levels. The previous 'classic' timer wheel
+ * implementation of the kernel already violated the 'exact' expiry by adding
+ * slack to the expiry time to provide batched expiration. The granularity
+ * levels provide implicit batching.
+ *
+ * This is an optimization of the original timer wheel implementation for the
+ * majority of the timer wheel use cases: timeouts. The vast majority of
+ * timeout timers (networking, disk I/O ...) are canceled before expiry. If
+ * the timeout expires it indicates that normal operation is disturbed, so it
+ * does not matter much whether the timeout comes with a slight delay.
+ *
+ * The only exception to this are networking timers with a small expiry
+ * time. They rely on the granularity. Those fit into the first wheel level,
+ * which has HZ granularity.
+ *
+ * We don't have cascading anymore. timers with a expiry time above the
+ * capacity of the last wheel level are force expired at the maximum timeout
+ * value of the last wheel level. From data sampling we know that the maximum
+ * value observed is 5 days (network connection tracking), so this should not
+ * be an issue.
+ *
+ * The currently chosen array constants values are a good compromise between
+ * array size and granularity.
+ *
+ * This results in the following granularity and range levels:
+ *
+ * HZ 1000 steps
+ * Level Offset Granularity Range
+ * 0 0 1 ms 0 ms - 63 ms
+ * 1 64 8 ms 64 ms - 511 ms
+ * 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
+ * 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
+ * 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
+ * 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
+ * 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
+ * 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
+ * 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
+ *
+ * HZ 300
+ * Level Offset Granularity Range
+ * 0 0 3 ms 0 ms - 210 ms
+ * 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
+ * 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
+ * 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
+ * 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
+ * 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
+ * 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
+ * 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
+ * 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
+ *
+ * HZ 250
+ * Level Offset Granularity Range
+ * 0 0 4 ms 0 ms - 255 ms
+ * 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
+ * 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
+ * 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
+ * 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
+ * 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
+ * 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
+ * 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
+ * 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
+ *
+ * HZ 100
+ * Level Offset Granularity Range
+ * 0 0 10 ms 0 ms - 630 ms
+ * 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
+ * 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
+ * 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
+ * 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
+ * 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
+ * 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
+ * 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
*/
-#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
-#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
-#define TVN_SIZE (1 << TVN_BITS)
-#define TVR_SIZE (1 << TVR_BITS)
-#define TVN_MASK (TVN_SIZE - 1)
-#define TVR_MASK (TVR_SIZE - 1)
-#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))
-
-struct tvec {
- struct hlist_head vec[TVN_SIZE];
-};
-struct tvec_root {
- struct hlist_head vec[TVR_SIZE];
-};
+/* Clock divisor for the next level */
+#define LVL_CLK_SHIFT 3
+#define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
+#define LVL_CLK_MASK (LVL_CLK_DIV - 1)
+#define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
+#define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
+
+/*
+ * The time start value for each level to select the bucket at enqueue
+ * time.
+ */
+#define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
+
+/* Size of each clock level */
+#define LVL_BITS 6
+#define LVL_SIZE (1UL << LVL_BITS)
+#define LVL_MASK (LVL_SIZE - 1)
+#define LVL_OFFS(n) ((n) * LVL_SIZE)
+
+/* Level depth */
+#if HZ > 100
+# define LVL_DEPTH 9
+# else
+# define LVL_DEPTH 8
+#endif
+
+/* The cutoff (max. capacity of the wheel) */
+#define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
+#define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
+
+/*
+ * The resulting wheel size. If NOHZ is configured we allocate two
+ * wheels so we have a separate storage for the deferrable timers.
+ */
+#define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
+
+#ifdef CONFIG_NO_HZ_COMMON
+# define NR_BASES 2
+# define BASE_STD 0
+# define BASE_DEF 1
+#else
+# define NR_BASES 1
+# define BASE_STD 0
+# define BASE_DEF 0
+#endif
struct timer_base {
- spinlock_t lock;
- struct timer_list *running_timer;
- unsigned long clk;
- unsigned long next_timer;
- unsigned long active_timers;
- unsigned long all_timers;
- int cpu;
- bool migration_enabled;
- bool nohz_active;
- struct tvec_root tv1;
- struct tvec tv2;
- struct tvec tv3;
- struct tvec tv4;
- struct tvec tv5;
+ spinlock_t lock;
+ struct timer_list *running_timer;
+ unsigned long clk;
+ unsigned int cpu;
+ bool migration_enabled;
+ bool nohz_active;
+ DECLARE_BITMAP(pending_map, WHEEL_SIZE);
+ struct hlist_head vectors[WHEEL_SIZE];
} ____cacheline_aligned;
-
-static DEFINE_PER_CPU(struct timer_base, timer_bases);
+static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
unsigned int sysctl_timer_migration = 1;
@@ -106,15 +214,17 @@ void timers_update_migration(bool update_nohz)
unsigned int cpu;
/* Avoid the loop, if nothing to update */
- if (this_cpu_read(timer_bases.migration_enabled) == on)
+ if (this_cpu_read(timer_bases[BASE_STD].migration_enabled) == on)
return;
for_each_possible_cpu(cpu) {
- per_cpu(timer_bases.migration_enabled, cpu) = on;
+ per_cpu(timer_bases[BASE_STD].migration_enabled, cpu) = on;
+ per_cpu(timer_bases[BASE_DEF].migration_enabled, cpu) = on;
per_cpu(hrtimer_bases.migration_enabled, cpu) = on;
if (!update_nohz)
continue;
- per_cpu(timer_bases.nohz_active, cpu) = true;
+ per_cpu(timer_bases[BASE_STD].nohz_active, cpu) = true;
+ per_cpu(timer_bases[BASE_DEF].nohz_active, cpu) = true;
per_cpu(hrtimer_bases.nohz_active, cpu) = true;
}
}
@@ -133,20 +243,6 @@ int timer_migration_handler(struct ctl_table *table, int write,
mutex_unlock(&mutex);
return ret;
}
-
-static inline struct timer_base *get_target_base(struct timer_base *base,
- int pinned)
-{
- if (pinned || !base->migration_enabled)
- return this_cpu_ptr(&timer_bases);
- return per_cpu_ptr(&timer_bases, get_nohz_timer_target());
-}
-#else
-static inline struct timer_base *get_target_base(struct timer_base *base,
- int pinned)
-{
- return this_cpu_ptr(&timer_bases);
-}
#endif
static unsigned long round_jiffies_common(unsigned long j, int cpu,
@@ -370,78 +466,91 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
}
EXPORT_SYMBOL_GPL(set_timer_slack);
+static inline unsigned int timer_get_idx(struct timer_list *timer)
+{
+ return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
+}
+
+static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
+{
+ timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
+ idx << TIMER_ARRAYSHIFT;
+}
+
+/*
+ * Helper function to calculate the array index for a given expiry
+ * time.
+ */
+static inline unsigned calc_index(unsigned expires, unsigned lvl)
+{
+ expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
+ return LVL_OFFS(lvl) + (expires & LVL_MASK);
+}
+
static void
__internal_add_timer(struct timer_base *base, struct timer_list *timer)
{
unsigned long expires = timer->expires;
- unsigned long idx = expires - base->clk;
+ unsigned long delta = expires - base->clk;
struct hlist_head *vec;
-
- if (idx < TVR_SIZE) {
- int i = expires & TVR_MASK;
- vec = base->tv1.vec + i;
- } else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
- int i = (expires >> TVR_BITS) & TVN_MASK;
- vec = base->tv2.vec + i;
- } else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
- int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
- vec = base->tv3.vec + i;
- } else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
- int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
- vec = base->tv4.vec + i;
- } else if ((signed long) idx < 0) {
- /*
- * Can happen if you add a timer with expires == jiffies,
- * or you set a timer to go off in the past
- */
- vec = base->tv1.vec + (base->clk & TVR_MASK);
+ unsigned int idx;
+
+ if (delta < LVL_START(1)) {
+ idx = calc_index(expires, 0);
+ } else if (delta < LVL_START(2)) {
+ idx = calc_index(expires, 1);
+ } else if (delta < LVL_START(3)) {
+ idx = calc_index(expires, 2);
+ } else if (delta < LVL_START(4)) {
+ idx = calc_index(expires, 3);
+ } else if (delta < LVL_START(5)) {
+ idx = calc_index(expires, 4);
+ } else if (delta < LVL_START(6)) {
+ idx = calc_index(expires, 5);
+ } else if (delta < LVL_START(7)) {
+ idx = calc_index(expires, 6);
+ } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
+ idx = calc_index(expires, 7);
+ } else if ((long) delta < 0) {
+ idx = base->clk & LVL_MASK;
} else {
- int i;
- /* If the timeout is larger than MAX_TVAL (on 64-bit
- * architectures or with CONFIG_BASE_SMALL=1) then we
- * use the maximum timeout.
+ /*
+ * Force expire obscene large timeouts to expire at the
+ * capacity limit of the wheel.
*/
- if (idx > MAX_TVAL) {
- idx = MAX_TVAL;
- expires = idx + base->clk;
- }
- i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
- vec = base->tv5.vec + i;
- }
+ if (expires >= WHEEL_TIMEOUT_CUTOFF)
+ expires = WHEEL_TIMEOUT_MAX;
+ idx = calc_index(expires, LVL_DEPTH - 1);
+ }
+ /*
+ * Enqueue the timer into the array bucket, mark it pending in
+ * the bitmap and store the index in the timer flags.
+ */
+ vec = base->vectors + idx;
hlist_add_head(&timer->entry, vec);
+ __set_bit(idx, base->pending_map);
+ timer_set_idx(timer, idx);
}
static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
{
- /* Advance base->jiffies, if the base is empty */
- if (!base->all_timers++)
- base->clk = jiffies;
-
__internal_add_timer(base, timer);
- /*
- * Update base->active_timers and base->next_timer
- */
- if (!(timer->flags & TIMER_DEFERRABLE)) {
- if (!base->active_timers++ ||
- time_before(timer->expires, base->next_timer))
- base->next_timer = timer->expires;
- }
/*
* Check whether the other CPU is in dynticks mode and needs
- * to be triggered to reevaluate the timer wheel.
- * We are protected against the other CPU fiddling
- * with the timer by holding the timer base lock. This also
- * makes sure that a CPU on the way to stop its tick can not
- * evaluate the timer wheel.
+ * to be triggered to reevaluate the timer wheel. We are
+ * protected against the other CPU fiddling with the timer by
+ * holding the timer base lock. This also makes sure that a
+ * CPU on the way to stop its tick can not evaluate the timer
+ * wheel.
*
* Spare the IPI for deferrable timers on idle targets though.
* The next busy ticks will take care of it. Except full dynticks
* require special care against races with idle_cpu(), lets deal
* with that later.
*/
- if (base->nohz_active) {
+ if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active) {
if (!(timer->flags & TIMER_DEFERRABLE) ||
tick_nohz_full_cpu(base->cpu))
wake_up_nohz_cpu(base->cpu);
@@ -706,54 +815,87 @@ static inline void detach_timer(struct timer_list *timer, bool clear_pending)
entry->next = LIST_POISON2;
}
-static inline void
-detach_expired_timer(struct timer_list *timer, struct timer_base *base)
-{
- detach_timer(timer, true);
- if (!(timer->flags & TIMER_DEFERRABLE))
- base->active_timers--;
- base->all_timers--;
-}
-
static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
bool clear_pending)
{
+ unsigned idx = timer_get_idx(timer);
+
if (!timer_pending(timer))
return 0;
+ if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
+ __clear_bit(idx, base->pending_map);
+
detach_timer(timer, clear_pending);
- if (!(timer->flags & TIMER_DEFERRABLE)) {
- base->active_timers--;
- if (timer->expires == base->next_timer)
- base->next_timer = base->clk;
- }
- /* If this was the last timer, advance base->jiffies */
- if (!--base->all_timers)
- base->clk = jiffies;
return 1;
}
+static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
+{
+ struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
+
+ /*
+ * If the timer is deferrable and nohz is active then we need to use
+ * the deferrable base.
+ */
+ if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active &&
+ (tflags & TIMER_DEFERRABLE))
+ base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
+ return base;
+}
+
+static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
+{
+ struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
+ /*
+ * If the timer is deferrable and nohz is active then we need to use
+ * the deferrable base.
+ */
+ if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active &&
+ (tflags & TIMER_DEFERRABLE))
+ base = this_cpu_ptr(&timer_bases[BASE_DEF]);
+ return base;
+}
+
+static inline struct timer_base *get_timer_base(u32 tflags)
+{
+ return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
+}
+
+static inline struct timer_base *get_target_base(struct timer_base *base,
+ unsigned tflags)
+{
+#if defined(CONFIG_NO_HZ_COMMON) && defined(CONFIG_SMP)
+ if ((tflags & TIMER_PINNED) || !base->migration_enabled)
+ return get_timer_this_cpu_base(tflags);
+ return get_timer_cpu_base(tflags, get_nohz_timer_target());
+#else
+ return get_timer_this_cpu_base(tflags);
+#endif
+}
+
/*
- * We are using hashed locking: holding per_cpu(timer_bases).lock
- * means that all timers which are tied to this base via timer->base are
- * locked, and the base itself is locked too.
+ * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
+ * that all timers which are tied to this base are locked, and the base itself
+ * is locked too.
*
* So __run_timers/migrate_timers can safely modify all timers which could
- * be found on ->tvX lists.
+ * be found in the base->vectors array.
*
- * When the timer's base is locked and removed from the list, the
- * TIMER_MIGRATING flag is set, FIXME
+ * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
+ * to wait until the migration is done.
*/
static struct timer_base *lock_timer_base(struct timer_list *timer,
- unsigned long *flags)
+ unsigned long *flags)
__acquires(timer->base->lock)
{
for (;;) {
- u32 tf = timer->flags;
struct timer_base *base;
+ u32 tf = timer->flags;
if (!(tf & TIMER_MIGRATING)) {
- base = per_cpu_ptr(&timer_bases, tf & TIMER_CPUMASK);
+ base = get_timer_base(tf);
spin_lock_irqsave(&base->lock, *flags);
if (timer->flags == tf)
return base;
@@ -770,6 +912,27 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
unsigned long flags;
int ret = 0;
+ /*
+ * TODO: Calculate the array bucket of the timer right here w/o
+ * holding the base lock. This allows to check not only
+ * timer->expires == expires below, but also whether the timer
+ * ends up in the same bucket. If we really need to requeue
+ * the timer then we check whether base->clk have
+ * advanced between here and locking the timer base. If
+ * jiffies advanced we have to recalc the array bucket with the
+ * lock held.
+ */
+
+ /*
+ * This is a common optimization triggered by the
+ * networking code - if the timer is re-modified
+ * to be the same thing then just return:
+ */
+ if (timer_pending(timer)) {
+ if (timer->expires == expires)
+ return 1;
+ }
+
timer_stats_timer_set_start_info(timer);
BUG_ON(!timer->function);
@@ -781,15 +944,15 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
debug_activate(timer, expires);
- new_base = get_target_base(base, timer->flags & TIMER_PINNED);
+ new_base = get_target_base(base, timer->flags);
if (base != new_base) {
/*
- * We are trying to schedule the timer on the local CPU.
+ * We are trying to schedule the timer on the new base.
* However we can't change timer's base while it is running,
* otherwise del_timer_sync() can't detect that the timer's
- * handler yet has not finished. This also guarantees that
- * the timer is serialized wrt itself.
+ * handler yet has not finished. This also guarantees that the
+ * timer is serialized wrt itself.
*/
if (likely(base->running_timer != timer)) {
/* See the comment in lock_timer_base() */
@@ -828,45 +991,6 @@ int mod_timer_pending(struct timer_list *timer, unsigned long expires)
}
EXPORT_SYMBOL(mod_timer_pending);
-/*
- * Decide where to put the timer while taking the slack into account
- *
- * Algorithm:
- * 1) calculate the maximum (absolute) time
- * 2) calculate the highest bit where the expires and new max are different
- * 3) use this bit to make a mask
- * 4) use the bitmask to round down the maximum time, so that all last
- * bits are zeros
- */
-static inline
-unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
-{
- unsigned long expires_limit, mask;
- int bit;
-
- if (timer->slack >= 0) {
- expires_limit = expires + timer->slack;
- } else {
- long delta = expires - jiffies;
-
- if (delta < 256)
- return expires;
-
- expires_limit = expires + delta / 256;
- }
- mask = expires ^ expires_limit;
- if (mask == 0)
- return expires;
-
- bit = __fls(mask);
-
- mask = (1UL << bit) - 1;
-
- expires_limit = expires_limit & ~(mask);
-
- return expires_limit;
-}
-
/**
* mod_timer - modify a timer's timeout
* @timer: the timer to be modified
@@ -889,16 +1013,6 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
*/
int mod_timer(struct timer_list *timer, unsigned long expires)
{
- expires = apply_slack(timer, expires);
-
- /*
- * This is a common optimization triggered by the
- * networking code - if the timer is re-modified
- * to be the same thing then just return:
- */
- if (timer_pending(timer) && timer->expires == expires)
- return 1;
-
return __mod_timer(timer, expires, false);
}
EXPORT_SYMBOL(mod_timer);
@@ -933,13 +1047,14 @@ EXPORT_SYMBOL(add_timer);
*/
void add_timer_on(struct timer_list *timer, int cpu)
{
- struct timer_base *new_base = per_cpu_ptr(&timer_bases, cpu);
- struct timer_base *base;
+ struct timer_base *new_base, *base;
unsigned long flags;
timer_stats_timer_set_start_info(timer);
BUG_ON(timer_pending(timer) || !timer->function);
+ new_base = get_timer_cpu_base(timer->flags, cpu);
+
/*
* If @timer was on a different CPU, it should be migrated with the
* old base locked to prevent other operations proceeding with the
@@ -1085,27 +1200,6 @@ int del_timer_sync(struct timer_list *timer)
EXPORT_SYMBOL(del_timer_sync);
#endif
-static int cascade(struct timer_base *base, struct tvec *tv, int index)
-{
- /* cascade all the timers from tv up one level */
- struct timer_list *timer;
- struct hlist_node *tmp;
- struct hlist_head 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.
- */
- hlist_for_each_entry_safe(timer, tmp, &tv_list, entry) {
- /* No accounting, while moving them */
- __internal_add_timer(base, timer);
- }
-
- return index;
-}
-
static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
unsigned long data)
{
@@ -1149,68 +1243,80 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
}
}
-#define INDEX(N) ((base->clk >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
+static void expire_timers(struct timer_base *base, struct hlist_head *head)
+{
+ while (!hlist_empty(head)) {
+ struct timer_list *timer;
+ void (*fn)(unsigned long);
+ unsigned long data;
+
+ timer = hlist_entry(head->first, struct timer_list, entry);
+ timer_stats_account_timer(timer);
+
+ base->running_timer = timer;
+ detach_timer(timer, true);
+
+ fn = timer->function;
+ data = timer->data;
+
+ if (timer->flags & TIMER_IRQSAFE) {
+ spin_unlock(&base->lock);
+ call_timer_fn(timer, fn, data);
+ spin_lock(&base->lock);
+ } else {
+ spin_unlock_irq(&base->lock);
+ call_timer_fn(timer, fn, data);
+ spin_lock_irq(&base->lock);
+ }
+ }
+}
+
+static int collect_expired_timers(struct timer_base *base,
+ struct hlist_head *heads)
+{
+ unsigned long clk = base->clk;
+ struct hlist_head *vec;
+ int i, levels = 0;
+ unsigned int idx;
+
+ for (i = 0; i < LVL_DEPTH; i++) {
+ idx = (clk & LVL_MASK) + i * LVL_SIZE;
+
+ if (__test_and_clear_bit(idx, base->pending_map)) {
+ vec = base->vectors + idx;
+ hlist_move_list(vec, heads++);
+ levels++;
+ }
+ /* Is it time to look at the next level? */
+ if (clk & LVL_CLK_MASK)
+ break;
+ /* Shift clock for the next level granularity */
+ clk >>= LVL_CLK_SHIFT;
+ }
+ return levels;
+}
/**
* __run_timers - run all expired timers (if any) on this CPU.
* @base: the timer vector to be processed.
- *
- * This function cascades all vectors and executes all expired timer
- * vectors.
*/
static inline void __run_timers(struct timer_base *base)
{
- struct timer_list *timer;
+ struct hlist_head heads[LVL_DEPTH];
+ int levels;
+
+ if (!time_after_eq(jiffies, base->clk))
+ return;
spin_lock_irq(&base->lock);
while (time_after_eq(jiffies, base->clk)) {
- struct hlist_head work_list;
- struct hlist_head *head = &work_list;
- int index;
- if (!base->all_timers) {
- base->clk = jiffies;
- break;
- }
-
- index = base->clk & TVR_MASK;
+ levels = collect_expired_timers(base, heads);
+ base->clk++;
- /*
- * Cascade timers:
- */
- if (!index &&
- (!cascade(base, &base->tv2, INDEX(0))) &&
- (!cascade(base, &base->tv3, INDEX(1))) &&
- !cascade(base, &base->tv4, INDEX(2)))
- cascade(base, &base->tv5, INDEX(3));
- ++base->clk;
- hlist_move_list(base->tv1.vec + index, head);
- while (!hlist_empty(head)) {
- void (*fn)(unsigned long);
- unsigned long data;
- bool irqsafe;
-
- timer = hlist_entry(head->first, struct timer_list, entry);
- fn = timer->function;
- data = timer->data;
- irqsafe = timer->flags & TIMER_IRQSAFE;
-
- timer_stats_account_timer(timer);
-
- base->running_timer = timer;
- detach_expired_timer(timer, base);
-
- if (irqsafe) {
- spin_unlock(&base->lock);
- call_timer_fn(timer, fn, data);
- spin_lock(&base->lock);
- } else {
- spin_unlock_irq(&base->lock);
- call_timer_fn(timer, fn, data);
- spin_lock_irq(&base->lock);
- }
- }
+ while (levels--)
+ expire_timers(base, heads + levels);
}
base->running_timer = NULL;
spin_unlock_irq(&base->lock);
@@ -1218,78 +1324,87 @@ static inline void __run_timers(struct timer_base *base)
#ifdef CONFIG_NO_HZ_COMMON
/*
- * Find out when the next timer event is due to happen. This
- * is used on S/390 to stop all activity when a CPU is idle.
- * This function needs to be called with interrupts disabled.
+ * Find the next pending bucket of a level. Search from @offset + @clk upwards
+ * and if nothing there, search from start of the level (@offset) up to
+ * @offset + clk.
+ */
+static int next_pending_bucket(struct timer_base *base, unsigned offset,
+ unsigned clk)
+{
+ unsigned pos, start = offset + clk;
+ unsigned end = offset + LVL_SIZE;
+
+ pos = find_next_bit(base->pending_map, end, start);
+ if (pos < end)
+ return pos - start;
+
+ pos = find_next_bit(base->pending_map, start, offset);
+ return pos < start ? pos + LVL_SIZE - start : -1;
+}
+
+/*
+ * Search the first expiring timer in the various clock levels.
*/
static unsigned long __next_timer_interrupt(struct timer_base *base)
{
- unsigned long clk = base->clk;
- unsigned long expires = clk + NEXT_TIMER_MAX_DELTA;
- int index, slot, array, found = 0;
- struct timer_list *nte;
- struct tvec *varray[4];
-
- /* Look for timer events in tv1. */
- index = slot = clk & TVR_MASK;
- do {
- hlist_for_each_entry(nte, base->tv1.vec + slot, entry) {
- if (nte->flags & TIMER_DEFERRABLE)
- continue;
-
- found = 1;
- expires = nte->expires;
- /* Look at the cascade bucket(s)? */
- if (!index || slot < index)
- goto cascade;
- return expires;
+ unsigned long clk, next, adj;
+ unsigned lvl, offset = 0;
+
+ spin_lock(&base->lock);
+ next = base->clk + NEXT_TIMER_MAX_DELTA;
+ clk = base->clk;
+ for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
+ int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
+
+ if (pos >= 0) {
+ unsigned long tmp = clk + (unsigned long) pos;
+
+ tmp <<= LVL_SHIFT(lvl);
+ if (time_before(tmp, next))
+ next = tmp;
}
- slot = (slot + 1) & TVR_MASK;
- } while (slot != index);
-
-cascade:
- /* Calculate the next cascade event */
- if (index)
- clk += TVR_SIZE - index;
- clk >>= TVR_BITS;
-
- /* Check tv2-tv5. */
- varray[0] = &base->tv2;
- varray[1] = &base->tv3;
- varray[2] = &base->tv4;
- varray[3] = &base->tv5;
-
- for (array = 0; array < 4; array++) {
- struct tvec *varp = varray[array];
-
- index = slot = clk & TVN_MASK;
- do {
- hlist_for_each_entry(nte, varp->vec + slot, entry) {
- if (nte->flags & TIMER_DEFERRABLE)
- continue;
-
- found = 1;
- if (time_before(nte->expires, expires))
- expires = nte->expires;
- }
- /*
- * Do we still search for the first timer or are
- * we looking up the cascade buckets ?
- */
- if (found) {
- /* Look at the cascade bucket(s)? */
- if (!index || slot < index)
- break;
- return expires;
- }
- slot = (slot + 1) & TVN_MASK;
- } while (slot != index);
-
- if (index)
- clk += TVN_SIZE - index;
- clk >>= TVN_BITS;
+ /*
+ * Clock for the next level. If the current level clock lower
+ * bits are zero, we look at the next level as is. If not we
+ * need to advance it by one because that's going to be the
+ * next expiring bucket in that level. base->clk is the next
+ * expiring jiffie. So in case of:
+ *
+ * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+ * 0 0 0 0 0 0
+ *
+ * we have to look at all levels @index 0. With
+ *
+ * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+ * 0 0 0 0 0 2
+ *
+ * LVL0 has the next expiring bucket @index 2. The upper
+ * levels have the next expiring bucket @index 1.
+ *
+ * In case that the propagation wraps the next level the same
+ * rules apply:
+ *
+ * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+ * 0 0 0 0 F 2
+ *
+ * So after looking at LVL0 we get:
+ *
+ * LVL5 LVL4 LVL3 LVL2 LVL1
+ * 0 0 0 1 0
+ *
+ * So no propagation from LVL1 to LVL2 because that happened
+ * with the add already, but then we need to propagate further
+ * from LVL2 to LVL3.
+ *
+ * So the simple check whether the lower bits of the current
+ * level are 0 or not is sufficient for all cases.
+ */
+ adj = clk & LVL_CLK_MASK ? 1 : 0;
+ clk >>= LVL_CLK_SHIFT;
+ clk += adj;
}
- return expires;
+ spin_unlock(&base->lock);
+ return next;
}
/*
@@ -1335,7 +1450,7 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
*/
u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
{
- struct timer_base *base = this_cpu_ptr(&timer_bases);
+ struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
u64 expires = KTIME_MAX;
unsigned long nextevt;
@@ -1346,17 +1461,11 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
if (cpu_is_offline(smp_processor_id()))
return expires;
- spin_lock(&base->lock);
- if (base->active_timers) {
- if (time_before_eq(base->next_timer, base->clk))
- base->next_timer = __next_timer_interrupt(base);
- nextevt = base->next_timer;
- if (time_before_eq(nextevt, basej))
- expires = basem;
- else
- expires = basem + (nextevt - basej) * TICK_NSEC;
- }
- spin_unlock(&base->lock);
+ nextevt = __next_timer_interrupt(base);
+ if (time_before_eq(nextevt, basej))
+ expires = basem;
+ else
+ expires = basem + (nextevt - basej) * TICK_NSEC;
return cmp_next_hrtimer_event(basem, expires);
}
@@ -1387,10 +1496,11 @@ void update_process_times(int user_tick)
*/
static void run_timer_softirq(struct softirq_action *h)
{
- struct timer_base *base = this_cpu_ptr(&timer_bases);
+ struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
- if (time_after_eq(jiffies, base->clk))
- __run_timers(base);
+ __run_timers(base);
+ if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active)
+ __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
}
/*
@@ -1541,7 +1651,6 @@ static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *h
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->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
internal_add_timer(new_base, timer);
@@ -1552,35 +1661,29 @@ static void migrate_timers(int cpu)
{
struct timer_base *old_base;
struct timer_base *new_base;
- int i;
+ int b, i;
BUG_ON(cpu_online(cpu));
- old_base = per_cpu_ptr(&timer_bases, cpu);
- new_base = get_cpu_ptr(&timer_bases);
- /*
- * The caller is globally serialized and nobody else
- * takes two locks at once, deadlock is not possible.
- */
- spin_lock_irq(&new_base->lock);
- spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
-
- BUG_ON(old_base->running_timer);
-
- for (i = 0; i < TVR_SIZE; i++)
- migrate_timer_list(new_base, old_base->tv1.vec + i);
- for (i = 0; i < TVN_SIZE; i++) {
- migrate_timer_list(new_base, old_base->tv2.vec + i);
- migrate_timer_list(new_base, old_base->tv3.vec + i);
- migrate_timer_list(new_base, old_base->tv4.vec + i);
- migrate_timer_list(new_base, old_base->tv5.vec + i);
- }
- old_base->active_timers = 0;
- old_base->all_timers = 0;
+ for (b = 0; b < NR_BASES; b++) {
+ old_base = per_cpu_ptr(&timer_bases[b], cpu);
+ new_base = get_cpu_ptr(&timer_bases[b]);
+ /*
+ * The caller is globally serialized and nobody else
+ * takes two locks at once, deadlock is not possible.
+ */
+ spin_lock_irq(&new_base->lock);
+ spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+
+ BUG_ON(old_base->running_timer);
+
+ for (i = 0; i < WHEEL_SIZE; i++)
+ migrate_timer_list(new_base, old_base->vectors + i);
- spin_unlock(&old_base->lock);
- spin_unlock_irq(&new_base->lock);
- put_cpu_ptr(&timer_bases);
+ spin_unlock(&old_base->lock);
+ spin_unlock_irq(&new_base->lock);
+ put_cpu_ptr(&timer_bases);
+ }
}
static int timer_cpu_notify(struct notifier_block *self,
@@ -1608,13 +1711,15 @@ static inline void timer_register_cpu_notifier(void) { }
static void __init init_timer_cpu(int cpu)
{
- struct timer_base *base = per_cpu_ptr(&timer_bases, cpu);
-
- base->cpu = cpu;
- spin_lock_init(&base->lock);
+ struct timer_base *base;
+ int i;
- base->clk = jiffies;
- base->next_timer = base->clk;
+ for (i = 0; i < NR_BASES; i++) {
+ base = per_cpu_ptr(&timer_bases[i], cpu);
+ base->cpu = cpu;
+ spin_lock_init(&base->lock);
+ base->clk = jiffies;
+ }
}
static void __init init_timer_cpus(void)