diff options
Diffstat (limited to 'erts/emulator/beam/time.c')
| -rw-r--r-- | erts/emulator/beam/time.c | 1762 |
1 files changed, 1394 insertions, 368 deletions
diff --git a/erts/emulator/beam/time.c b/erts/emulator/beam/time.c index 2fd8e0cf00..a3069e419a 100644 --- a/erts/emulator/beam/time.c +++ b/erts/emulator/beam/time.c @@ -1,72 +1,173 @@ /* * %CopyrightBegin% * - * Copyright Ericsson AB 1996-2013. All Rights Reserved. + * Copyright Ericsson AB 1996-2017. All Rights Reserved. * - * The contents of this file are subject to the Erlang Public License, - * Version 1.1, (the "License"); you may not use this file except in - * compliance with the License. You should have received a copy of the - * Erlang Public License along with this software. If not, it can be - * retrieved online at http://www.erlang.org/. - * - * Software distributed under the License is distributed on an "AS IS" - * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See - * the License for the specific language governing rights and limitations - * under the License. + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. * * %CopyrightEnd% */ - + /* - * TIMING WHEEL + * TIMER WHEEL + * + * + * The time scale used for timers is Erlang monotonic time. The + * time unit used is ERTS specific clock ticks. A clock tick is + * currently defined to 1 millisecond. That is, the resolution of + * timers triggered by the runtime system is 1 millisecond. * - * Timeouts kept in an wheel. A timeout is measured relative to the - * current slot (tiw_pos) in the wheel, and inserted at slot - * (tiw_pos + timeout) % TIW_SIZE. Each timeout also has a count - * equal to timeout/TIW_SIZE, which is needed since the time axis - * is wrapped arount the wheel. + * When a timer is set, it is determined at what Erlang monotonic + * time, in clock ticks, it should be triggered. * - * Several slots may be processed in one operation. If the number of - * slots is greater that the wheel size, the wheel is only traversed - * once, + * The 'pos' field of the wheel corresponds to current time of + * the wheel. That is, it corresponds to Erlang monotonic time in + * clock tick time unit. The 'pos' field of the wheel is + * monotonically increased when erts_bump_timers() is called. All + * timers in the wheel that have a time less than or equal to + * 'pos' are triggered by the bump operation. The bump operation + * may however be spread over multiple calls to erts_bump_timers() + * if there are a lots of timers to trigger. * - * The following example shows a time axis where there is one timeout - * at each "tick", and where 1, 2, 3 ... wheel slots are released in - * one operation. The notation "<x" means "release all items with - * counts less than x". + * Each scheduler thread maintains its own timer wheel. The timer + * wheel of a scheduler, however, actually consists of two wheels. + * A soon wheel and a later wheel. + * + * + * -- The Soon Wheel -- + * + * The soon wheel contain timers that should be triggered soon. + * That is, they are soon to be triggered. Each slot in the soon + * wheel is 1 clock tick wide. The number of slots in the soon + * wheel is currently 2¹⁴. That is, it contains timers in the + * range ('pos', 'pos' + 2¹⁴] which corresponds to a bit more + * than 16 seconds. + * + * When the bump operation is started, 'pos' is moved forward to a + * position that corresponds to current Erlang monotonic time. Then + * all timers that are in the range (old 'pos', new 'pos'] are + * triggered. During a bump operation, the soon wheel may contain + * timers in the two, possibly overlapping, ranges (old 'pos', + * old 'pos' + 2¹⁴], and (new 'pos', new 'pos' + 2¹⁴]. This may + * occur even if the bump operation doesn't yield, due to timeout + * callbacks inserting new timers. + * + * + * -- The Later Wheel -- + * + * The later wheel contain timers that are further away from 'pos' + * than the width of the soon timer wheel. That is, currently + * timers further away from 'pos' than 2¹⁴ clock ticks. The width + * of each slot in the later wheel is half the width of the soon + * wheel. That is, each slot is currently 2¹³ clock ticks wide + * which corresponds to about 8 seconds. If three timers of the + * times 'pos' + 17000, 'pos' + 18000, and 'pos' + 19000 are + * inserted, they will all end up in the same slot in the later + * wheel. + * + * The number of slots in the later wheel is currently the same as + * in the soon wheel, i.e. 2¹⁴. That is, one revolution of the later + * wheel currently corresponds to 2¹⁴×2¹³ clock ticks which is + * almost 37 ½ hour. Timers even further away than that are put in + * the later slot identified by their time modulo the size of the later + * wheel. Such timers are however very uncommon. Most timers used + * by the runtime system will utilize the high level timer API. + * The high level timer implementation will not insert timers + * further away then one revolution into the later wheel. It will + * instead keep such timers in a tree of very long timers. The + * high level timer implementation utilize one timer wheel timer + * for the management of this tree of timers. This timer is set to + * the closest timeout in the tree. This timer may however be + * further away than one revolution in the later wheel. + * + * The 'later.pos' field identifies next position in the later wheel. + * 'later.pos' is always increased by the width of a later wheel slot. + * That is, currently 2¹³ clock ticks. When 'pos' is moved (during + * a bump operation) closer to 'later.pos' than the width of a later + * wheel slot, i.e. currently when 'pos' + 2¹³ ≥ 'later.pos', we + * inspect the slot identified by 'later.pos' and then move 'later.pos' + * forward. When inspecting the later slot we move all timers in the + * slot, that are in the soon wheel range, from the later wheel to + * the soon wheel. Timers one or more revolutions of the later wheel + * away are kept in the slot. + * + * During normal operation, timers originally located in the later + * wheel will currently be moved into the soon wheel about 8 to + * 16 seconds before they should be triggered. During extremely + * heavy load, the scheduler might however be heavily delayed, so + * the code must be prepared for situations where time for + * triggering the timer has passed when we inspect the later wheel + * slot, and then trigger the timer immediately. We must also be + * prepared to inspect multiple later wheel slots at once due to the + * delay. + * + * + * -- Slot Management -- + * + * All timers of a slot are placed in a circular double linked + * list. This makes insertion and removal of a timer O(1). + * + * While bumping timers in a slot, we move the circular list + * away from the slot, and refer to it from the 'sentinel' + * field. The list will stay there until we are done with it + * even if the bump operation should yield. The cancel operation + * can remove the timer from this position as well as from the + * slot position by just removing it from the circular double + * linked list that it is in. + * + * -- At Once Slot -- + * + * If a timer is set that has a time earlier or equal to 'pos', + * it is not inserted into the wheel. It is instead inserted, + * into a circular double linked list referred to by the "at + * once" slot. When the bump operation is performed these timers + * will be triggered at once. The circular list of the slot will + * be moved to the 'sentinel' field while bumping these timers + * as when bumping an ordinary wheel slot. A yielding bump + * operation and cancelation of timers is handled the same way + * as if the timer was in a wheel slot. + * + * -- Searching for Next Timeout -- + * + * In order to limit the amount of work needed in order to find + * next timeout, we keep track of total amount of timers in the + * wheels, total amount of timers in the later wheel, total amount + * of timers in soon wheel, and the total amount of timers in + * each range of slots. Each slot range currently contain 512 + * slots. + * + * When next timeout is less than the soon wheel width away we + * determine the exact timeout. Due to the timer counts of + * slot ranges, we currently at most need to search 1024 slots + * in the soon wheel. This besides inspecting slot range counts + * and two slots in the later wheel which potentially might trigger + * timeouts for moving timers from the later wheel to the soon wheel + * earlier than timeouts in the soon wheel. We also keep track + * of latest known minimum timeout position in each wheel which + * makes it possible to avoid scanning from current position + * each time. + * + * When next timeout is further away than the soon wheel width + * we settle for the earliest possible timeout in the first + * non-empty slot range. The further away the next timeout is, the + * more likely it is that the next timeout change before we + * actually get there. That is, a change due to another timer is + * set to an earlier time and/or the timer is cancelled. It is + * therefore in this case no point determining next timeout + * exactly. If the state should not change, we will wake up a bit + * early and do a recalculation of next timeout and eventually + * we will be so close to it that we determine it exactly. * - * Size of wheel: 4 - * - * --|----|----|----|----|----|----|----|----|----|----|----|----|---- - * 0.0 0.1 0.2 0.3 1.0 1.1 1.2 1.3 2.0 2.1 2.2 2.3 3.0 - * - * 1 [ ) - * <1 0.1 0.2 0.3 0.0 1.1 1.2 1.3 1.0 2.1 2.2 2.3 2.0 - * - * 2 [ ) - * <1 <1 0.2 0.3 0.0 0.1 1.2 1.3 1.0 1.1 2.2 2.3 2.0 - * - * 3 [ ) - * <1 <1 <1 0.3 0.0 0.1 0.2 1.3 1.0 1.1 1.2 2.3 2.0 - * - * 4 [ ) - * <1 <1 <1 <1 0.0 0.1 0.2 0.3 1.0 1.1 1.2 1.3 2.0 - * - * 5 [ ) - * <2 <1 <1 <1. 0.1 0.2 0.3 0.0 1.1 1.2 1.3 1.0 - * - * 6 [ ) - * <2 <2 <1 <1. 0.2 0.3 0.0 0.1 1.2 1.3 1.0 - * - * 7 [ ) - * <2 <2 <2 <1. 0.3 0.0 0.1 0.2 1.3 1.0 - * - * 8 [ ) - * <2 <2 <2 <2. 0.0 0.1 0.2 0.3 1.0 - * - * 9 [ ) - * <3 <2 <2 <2. 0.1 0.2 0.3 0.0 - * */ #ifdef HAVE_CONFIG_H @@ -76,6 +177,14 @@ #include "sys.h" #include "erl_vm.h" #include "global.h" +#define ERTS_WANT_TIMER_WHEEL_API +#include "erl_time.h" + +#define ERTS_MAX_CLKTCKS \ + ERTS_MONOTONIC_TO_CLKTCKS(ERTS_MONOTONIC_TIME_MAX) + +#define ERTS_CLKTCKS_WEEK \ + ERTS_MONOTONIC_TO_CLKTCKS(ERTS_SEC_TO_MONOTONIC(7*60*60*24)) #ifdef ERTS_ENABLE_LOCK_CHECK #define ASSERT_NO_LOCKED_LOCKS erts_lc_check_exact(NULL, 0) @@ -83,26 +192,75 @@ #define ASSERT_NO_LOCKED_LOCKS #endif -static erts_smp_mtx_t tiw_lock; +#if 0 +# define ERTS_TW_HARD_DEBUG +#endif +#if defined(ERTS_TW_HARD_DEBUG) && !defined(ERTS_TW_DEBUG) +# define ERTS_TW_DEBUG +#endif +#if defined(DEBUG) && !defined(ERTS_TW_DEBUG) +# define ERTS_TW_DEBUG +#endif -/* BEGIN tiw_lock protected variables -** -** The individual timer cells in tiw are also protected by the same mutex. -*/ +#undef ERTS_TW_ASSERT +#if defined(ERTS_TW_DEBUG) +# define ERTS_TW_ASSERT(E) ERTS_ASSERT(E) +#else +# define ERTS_TW_ASSERT(E) ((void) 1) +#endif -#ifdef SMALL_MEMORY -#define TIW_SIZE 8192 +#ifdef ERTS_TW_DEBUG +# define ERTS_TWHEEL_BUMP_YIELD_LIMIT 500 #else -#define TIW_SIZE 65536 /* timing wheel size (should be a power of 2) */ +# define ERTS_TWHEEL_BUMP_YIELD_LIMIT 10000 #endif -static ErlTimer** tiw; /* the timing wheel, allocated in init_time() */ -static Uint tiw_pos; /* current position in wheel */ -static Uint tiw_nto; /* number of timeouts in wheel */ -static Uint tiw_min; -static ErlTimer *tiw_min_ptr; +#define ERTS_TW_COST_SLOT 1 +#define ERTS_TW_COST_SLOT_MOVE 5 +#define ERTS_TW_COST_TIMEOUT 100 + +/* + * Every slot in the soon wheel is a clock tick (as defined + * by ERTS) wide. A clock tick is currently 1 milli second. + */ -/* END tiw_lock protected variables */ +#define ERTS_TW_SOON_WHEEL_FIRST_SLOT 0 +#define ERTS_TW_SOON_WHEEL_END_SLOT \ + (ERTS_TW_SOON_WHEEL_FIRST_SLOT + ERTS_TW_SOON_WHEEL_SIZE) + +#define ERTS_TW_SOON_WHEEL_MASK (ERTS_TW_SOON_WHEEL_SIZE-1) + +/* + * Every slot in the later wheel is as wide as half the size + * of the soon wheel. + */ + +#define ERTS_TW_LATER_WHEEL_SHIFT (ERTS_TW_SOON_WHEEL_BITS - 1) +#define ERTS_TW_LATER_WHEEL_SLOT_SIZE \ + ((ErtsMonotonicTime) (1 << ERTS_TW_LATER_WHEEL_SHIFT)) +#define ERTS_TW_LATER_WHEEL_POS_MASK \ + (~((ErtsMonotonicTime) (1 << ERTS_TW_LATER_WHEEL_SHIFT)-1)) + +#define ERTS_TW_LATER_WHEEL_FIRST_SLOT ERTS_TW_SOON_WHEEL_SIZE +#define ERTS_TW_LATER_WHEEL_END_SLOT \ + (ERTS_TW_LATER_WHEEL_FIRST_SLOT + ERTS_TW_LATER_WHEEL_SIZE) + +#define ERTS_TW_LATER_WHEEL_MASK (ERTS_TW_LATER_WHEEL_SIZE-1) + +#define ERTS_TW_SCNT_BITS 9 +#define ERTS_TW_SCNT_SHIFT +#define ERTS_TW_SCNT_SIZE \ + ((ERTS_TW_SOON_WHEEL_SIZE + ERTS_TW_LATER_WHEEL_SIZE) \ + >> ERTS_TW_SCNT_BITS) + +#ifdef __GNUC__ +#if ERTS_TW_SOON_WHEEL_BITS < ERTS_TW_SCNT_BITS +# warning Consider larger soon timer wheel +#endif +#if ERTS_TW_SOON_WHEEL_BITS < ERTS_TW_SCNT_BITS +# warning Consider larger later timer wheel +#endif +#endif /* Actual interval time chosen by sys_init_time() */ @@ -114,392 +272,1260 @@ static int tiw_itime; /* Constant after init */ # define TIW_ITIME tiw_itime #endif -erts_smp_atomic32_t do_time; /* set at clock interrupt */ -static ERTS_INLINE erts_short_time_t do_time_read(void) +const int etp_tw_soon_wheel_size = ERTS_TW_SOON_WHEEL_SIZE; +const ErtsMonotonicTime etp_tw_soon_wheel_mask = ERTS_TW_SOON_WHEEL_MASK; +const int etp_tw_soon_wheel_first_slot = ERTS_TW_SOON_WHEEL_FIRST_SLOT; + +const int etp_tw_later_wheel_size = ERTS_TW_LATER_WHEEL_SIZE; +const ErtsMonotonicTime etp_tw_later_wheel_slot_size = ERTS_TW_LATER_WHEEL_SLOT_SIZE; +const int etp_tw_later_wheel_shift = ERTS_TW_LATER_WHEEL_SHIFT; +const ErtsMonotonicTime etp_tw_later_wheel_mask = ERTS_TW_LATER_WHEEL_MASK; +const ErtsMonotonicTime etp_tw_later_wheel_pos_mask = ERTS_TW_LATER_WHEEL_POS_MASK; +const int etp_tw_later_wheel_first_slot = ERTS_TW_LATER_WHEEL_FIRST_SLOT; + +struct ErtsTimerWheel_ { + ErtsTWheelTimer *slots[1 /* At Once Slot */ + + ERTS_TW_SOON_WHEEL_SIZE /* Soon Wheel Slots */ + + ERTS_TW_LATER_WHEEL_SIZE]; /* Later Wheel Slots */ + ErtsTWheelTimer **w; + Sint scnt[ERTS_TW_SCNT_SIZE]; + Sint bump_scnt[ERTS_TW_SCNT_SIZE]; + ErtsMonotonicTime pos; + Uint nto; + struct { + Uint nto; + } at_once; + struct { + ErtsMonotonicTime min_tpos; + Uint nto; + } soon; + struct { + ErtsMonotonicTime min_tpos; + int min_tpos_slot; + ErtsMonotonicTime pos; + Uint nto; + } later; + int yield_slot; + int yield_slots_left; + ErtsTWheelTimer sentinel; + int true_next_timeout_time; + ErtsMonotonicTime next_timeout_pos; + ErtsMonotonicTime next_timeout_time; +}; + +#define ERTS_TW_SLOT_AT_ONCE (-1) + +#define ERTS_TW_BUMP_LATER_WHEEL(TIW) \ + ((tiw)->pos + ERTS_TW_LATER_WHEEL_SLOT_SIZE >= (TIW)->later.pos) + +static int bump_later_wheel(ErtsTimerWheel *tiw, int *yield_count_p); + +#ifdef ERTS_TW_DEBUG +#define ERTS_TW_DBG_VERIFY_EMPTY_SOON_SLOTS(TIW, TO_POS) \ + dbg_verify_empty_soon_slots((TIW), (TO_POS)) +#define ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(TIW, TO_POS) \ + dbg_verify_empty_later_slots((TIW), (TO_POS)) +void dbg_verify_empty_soon_slots(ErtsTimerWheel *, ErtsMonotonicTime); +void dbg_verify_empty_later_slots(ErtsTimerWheel *, ErtsMonotonicTime); +#else +#define ERTS_TW_DBG_VERIFY_EMPTY_SOON_SLOTS(TIW, TO_POS) +#define ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(TIW, TO_POS) +#endif + +static ERTS_INLINE int +scnt_get_ix(int slot) { - return erts_smp_atomic32_read_acqb(&do_time); + return slot >> ERTS_TW_SCNT_BITS; } -static ERTS_INLINE erts_short_time_t do_time_update(void) +static ERTS_INLINE void +scnt_inc(Sint *scnt, int slot) { - return do_time_read(); + scnt[slot >> ERTS_TW_SCNT_BITS]++; } -static ERTS_INLINE void do_time_init(void) +#ifdef ERTS_TW_HARD_DEBUG + +static ERTS_INLINE void +scnt_ix_inc(Sint *scnt, int six) +{ + scnt[six]++; +} + +#endif + +static ERTS_INLINE void +scnt_dec(Sint *scnt, int slot) { - erts_smp_atomic32_init_nob(&do_time, 0); + scnt[slot >> ERTS_TW_SCNT_BITS]--; + ERTS_TW_ASSERT(scnt[slot >> ERTS_TW_SCNT_BITS] >= 0); } -/* get the time (in units of TIW_ITIME) to the next timeout, - or -1 if there are no timeouts */ +static ERTS_INLINE void +scnt_ix_dec(Sint *scnt, int six) +{ + scnt[six]--; + ERTS_TW_ASSERT(scnt[six] >= 0); +} -static erts_short_time_t next_time_internal(void) /* PRE: tiw_lock taken by caller */ +static ERTS_INLINE void +scnt_wheel_next(int *slotp, int *leftp, ErtsMonotonicTime *posp, + int *sixp, Sint *scnt, int first_slot, + int end_slot, ErtsMonotonicTime slot_sz) { - int i, tm, nto; - Uint32 min; - ErlTimer* p; - erts_short_time_t dt; - - if (tiw_nto == 0) - return -1; /* no timeouts in wheel */ - - if (tiw_min_ptr) { - min = tiw_min; - dt = do_time_read(); - return ((min >= dt) ? (min - dt) : 0); + int slot = *slotp; + int left = *leftp; + int ix; + + ERTS_TW_ASSERT(*leftp >= 0); + + left--; + slot++; + if (slot == end_slot) + slot = first_slot; + ix = slot >> ERTS_TW_SCNT_BITS; + + while (!scnt[ix] && left > 0) { + int diff, old_slot = slot; + ix++; + slot = (ix << ERTS_TW_SCNT_BITS); + diff = slot - old_slot; + if (left < diff) { + slot = old_slot + left; + diff = left; + } + if (slot < end_slot) + left -= diff; + else { + left -= end_slot - old_slot; + slot = first_slot; + ix = slot >> ERTS_TW_SCNT_BITS; + } } - - /* start going through wheel to find next timeout */ - tm = nto = 0; - min = (Uint32) -1; /* max Uint32 */ - i = tiw_pos; - do { - p = tiw[i]; - while (p != NULL) { - nto++; - if (p->count == 0) { - /* found next timeout */ - dt = do_time_read(); - /* p->count is zero */ - tiw_min_ptr = p; - tiw_min = tm; - return ((tm >= dt) ? (tm - dt) : 0); - } else { - /* keep shortest time in 'min' */ - if (tm + p->count*TIW_SIZE < min) { - min = tm + p->count*TIW_SIZE; - tiw_min_ptr = p; - tiw_min = min; - } - } - p = p->next; - } - /* when we have found all timeouts the shortest time will be in min */ - if (nto == tiw_nto) break; - tm++; - i = (i + 1) % TIW_SIZE; - } while (i != tiw_pos); - dt = do_time_read(); - if (min <= (Uint32) dt) - return 0; - if ((min - (Uint32) dt) > (Uint32) ERTS_SHORT_TIME_T_MAX) - return ERTS_SHORT_TIME_T_MAX; - return (erts_short_time_t) (min - (Uint32) dt); + + ERTS_TW_ASSERT(left >= -1); + + if (posp) + *posp += slot_sz * ((ErtsMonotonicTime) (*leftp - left)); + if (sixp) + *sixp = slot >> ERTS_TW_SCNT_BITS; + *leftp = left; + *slotp = slot; +} + + +static ERTS_INLINE void +scnt_soon_wheel_next(int *slotp, int *leftp, ErtsMonotonicTime *posp, + int *sixp, Sint *scnt) +{ + scnt_wheel_next(slotp, leftp, posp, sixp, scnt, + ERTS_TW_SOON_WHEEL_FIRST_SLOT, + ERTS_TW_SOON_WHEEL_END_SLOT, 1); } -static void remove_timer(ErlTimer *p) { - /* first */ - if (!p->prev) { - tiw[p->slot] = p->next; - if(p->next) - p->next->prev = NULL; - } else { - p->prev->next = p->next; +static ERTS_INLINE void +scnt_later_wheel_next(int *slotp, int *leftp, ErtsMonotonicTime *posp, + int *sixp, Sint *scnt) +{ + scnt_wheel_next(slotp, leftp, posp, sixp, scnt, + ERTS_TW_LATER_WHEEL_FIRST_SLOT, + ERTS_TW_LATER_WHEEL_END_SLOT, + ERTS_TW_LATER_WHEEL_SLOT_SIZE); +} + + +static ERTS_INLINE int +soon_slot(ErtsMonotonicTime soon_pos) +{ + ErtsMonotonicTime slot = soon_pos; + slot &= ERTS_TW_SOON_WHEEL_MASK; + + ERTS_TW_ASSERT(ERTS_TW_SOON_WHEEL_FIRST_SLOT <= slot); + ERTS_TW_ASSERT(slot < ERTS_TW_SOON_WHEEL_END_SLOT); + + return (int) slot; +} + +static ERTS_INLINE int +later_slot(ErtsMonotonicTime later_pos) +{ + ErtsMonotonicTime slot = later_pos; + slot >>= ERTS_TW_LATER_WHEEL_SHIFT; + slot &= ERTS_TW_LATER_WHEEL_MASK; + slot += ERTS_TW_LATER_WHEEL_FIRST_SLOT; + + ERTS_TW_ASSERT(ERTS_TW_LATER_WHEEL_FIRST_SLOT <= slot); + ERTS_TW_ASSERT(slot < ERTS_TW_LATER_WHEEL_END_SLOT); + + return (int) slot; +} + +#ifdef ERTS_TW_HARD_DEBUG +#define ERTS_HARD_DBG_CHK_WHEELS(TIW, CHK_MIN_TPOS) \ + hrd_dbg_check_wheels((TIW), (CHK_MIN_TPOS)) +static void hrd_dbg_check_wheels(ErtsTimerWheel *tiw, int check_min_tpos); +#else +#define ERTS_HARD_DBG_CHK_WHEELS(TIW, CHK_MIN_TPOS) +#endif + +static ErtsMonotonicTime +find_next_timeout(ErtsSchedulerData *esdp, ErtsTimerWheel *tiw) +{ + int slot, slots; + int true_min_timeout = 0; + ErtsMonotonicTime min_timeout_pos; + + ERTS_TW_ASSERT(tiw->pos + ERTS_TW_LATER_WHEEL_SLOT_SIZE < tiw->later.pos + && tiw->later.pos <= tiw->pos + ERTS_TW_SOON_WHEEL_SIZE); + + ERTS_HARD_DBG_CHK_WHEELS(tiw, 0); + + ERTS_TW_ASSERT(tiw->yield_slot == ERTS_TW_SLOT_INACTIVE); + + if (tiw->nto == 0) { /* no timeouts in wheel */ + ErtsMonotonicTime curr_time = erts_get_monotonic_time(esdp); + tiw->pos = min_timeout_pos = ERTS_MONOTONIC_TO_CLKTCKS(curr_time); + tiw->later.pos = min_timeout_pos + ERTS_TW_SOON_WHEEL_SIZE; + tiw->later.pos &= ERTS_TW_LATER_WHEEL_POS_MASK; + min_timeout_pos += ERTS_CLKTCKS_WEEK; + goto done; } - /* last */ - if (!p->next) { - if (p->prev) - p->prev->next = NULL; - } else { - p->next->prev = p->prev; + ERTS_TW_ASSERT(tiw->soon.nto || tiw->later.nto); + + if (!tiw->soon.nto) { + ErtsMonotonicTime tpos, min_tpos; + + /* Search later wheel... */ + + min_tpos = tiw->later.min_tpos & ERTS_TW_LATER_WHEEL_POS_MASK; + + if (min_tpos <= tiw->later.pos) { + tpos = tiw->later.pos; + slots = ERTS_TW_LATER_WHEEL_SIZE; + } + else { + ErtsMonotonicTime tmp; + /* Don't inspect slots we know are empty... */ + tmp = min_tpos - tiw->later.pos; + tmp /= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + if (tmp >= ERTS_TW_LATER_WHEEL_SIZE) { + /* Timeout more than one revolution ahead... */ + + /* Pre-timeout for move from later to soon wheel... */ + min_timeout_pos = min_tpos - ERTS_TW_LATER_WHEEL_SLOT_SIZE; + goto done; + } + tpos = min_tpos; + ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(tiw, min_tpos); + slots = ERTS_TW_LATER_WHEEL_SIZE - ((int) tmp); + } + + slot = later_slot(tpos); + + /* + * We never search for an exact timeout in the + * later wheel, but instead settle for the first + * scnt range used. + */ + if (tiw->w[slot]) + true_min_timeout = 1; + else + scnt_later_wheel_next(&slot, &slots, &tpos, NULL, tiw->scnt); + + tiw->later.min_tpos = tpos; + tiw->later.min_tpos_slot = slot; + ERTS_TW_ASSERT(slot == later_slot(tpos)); + + /* Pre-timeout for move from later to soon wheel... */ + tpos -= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + min_timeout_pos = tpos; } + else { + ErtsMonotonicTime tpos; + /* Search soon wheel... */ + + min_timeout_pos = tiw->pos + ERTS_TW_SOON_WHEEL_SIZE; + + /* + * Besides inspecting the soon wheel we + * may also have to inspect two slots in the + * later wheel which potentially can trigger + * timeouts before timeouts in soon wheel... + */ + if (tiw->later.min_tpos > (tiw->later.pos + + 2*ERTS_TW_LATER_WHEEL_SLOT_SIZE)) { + ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS( + tiw, 2*ERTS_TW_LATER_WHEEL_SLOT_SIZE); + } + else { + int fslot; + tpos = tiw->later.pos; + tpos -= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + fslot = later_slot(tiw->later.pos); + if (tiw->w[fslot]) + min_timeout_pos = tpos; + else { + tpos += ERTS_TW_LATER_WHEEL_SLOT_SIZE; + if (tpos < min_timeout_pos) { + fslot++; + if (fslot == ERTS_TW_LATER_WHEEL_END_SLOT) + fslot = ERTS_TW_LATER_WHEEL_FIRST_SLOT; + if (tiw->w[fslot]) + min_timeout_pos = tpos; + } + } + } + + if (tiw->soon.min_tpos <= tiw->pos) { + tpos = tiw->pos; + slots = ERTS_TW_SOON_WHEEL_SIZE; + } + else { + ErtsMonotonicTime tmp; + /* Don't inspect slots we know are empty... */ + tmp = tiw->soon.min_tpos - tiw->pos; + ERTS_TW_ASSERT(ERTS_TW_SOON_WHEEL_SIZE > tmp); + ERTS_TW_DBG_VERIFY_EMPTY_SOON_SLOTS(tiw, tiw->soon.min_tpos); + slots = ERTS_TW_SOON_WHEEL_SIZE - ((int) tmp); + tpos = tiw->soon.min_tpos; + } + + slot = soon_slot(tpos); + + /* find next non-empty slot */ + while (tpos < min_timeout_pos) { + if (tiw->w[slot]) { + ERTS_TW_ASSERT(tiw->w[slot]->timeout_pos == tpos); + min_timeout_pos = tpos; + break; + } + scnt_soon_wheel_next(&slot, &slots, &tpos, NULL, tiw->scnt); + } + + tiw->soon.min_tpos = min_timeout_pos; + true_min_timeout = 1; + } + +done: { + ErtsMonotonicTime min_timeout; + + min_timeout = ERTS_CLKTCKS_TO_MONOTONIC(min_timeout_pos); + tiw->next_timeout_pos = min_timeout_pos; + tiw->next_timeout_time = min_timeout; + tiw->true_next_timeout_time = true_min_timeout; + + ERTS_HARD_DBG_CHK_WHEELS(tiw, 1); - p->next = NULL; - p->prev = NULL; - /* Make sure cancel callback isn't called */ - p->active = 0; - tiw_nto--; + return min_timeout; + } +} + +static ERTS_INLINE void +insert_timer_into_slot(ErtsTimerWheel *tiw, int slot, ErtsTWheelTimer *p) +{ + ERTS_TW_ASSERT(ERTS_TW_SLOT_AT_ONCE <= slot + && slot < ERTS_TW_LATER_WHEEL_END_SLOT); + p->slot = slot; + if (!tiw->w[slot]) { + tiw->w[slot] = p; + p->next = p; + p->prev = p; + } + else { + ErtsTWheelTimer *next, *prev; + next = tiw->w[slot]; + prev = next->prev; + p->next = next; + p->prev = prev; + prev->next = p; + next->prev = p; + } + if (slot == ERTS_TW_SLOT_AT_ONCE) + tiw->at_once.nto++; + else { + ErtsMonotonicTime tpos = p->timeout_pos; + if (slot < ERTS_TW_SOON_WHEEL_END_SLOT) { + ERTS_TW_ASSERT(p->timeout_pos < tiw->pos + ERTS_TW_SOON_WHEEL_SIZE); + tiw->soon.nto++; + if (tiw->soon.min_tpos > tpos) + tiw->soon.min_tpos = tpos; + } + else { + ERTS_TW_ASSERT(p->timeout_pos >= tiw->pos + ERTS_TW_SOON_WHEEL_SIZE); + tiw->later.nto++; + if (tiw->later.min_tpos > tpos) { + tiw->later.min_tpos = tpos; + tiw->later.min_tpos_slot = slot; + } + } + scnt_inc(tiw->scnt, slot); + } +} + +static ERTS_INLINE void +remove_timer(ErtsTimerWheel *tiw, ErtsTWheelTimer *p) +{ + int slot = p->slot; + int empty_slot; + ERTS_TW_ASSERT(slot != ERTS_TW_SLOT_INACTIVE); + + /* + * Timer is in circular list either referred to + * by at once slot, slot in soon wheel, slot + * in later wheel, or by sentinel (timers currently + * being triggered). + */ + ERTS_TW_ASSERT(ERTS_TW_SLOT_AT_ONCE <= slot + && slot < ERTS_TW_LATER_WHEEL_END_SLOT); + + if (p->next == p) { + /* Cannot be referred by sentinel, i.e. must be referred by slot... */ + ERTS_TW_ASSERT(tiw->w[slot] == p); + tiw->w[slot] = NULL; + empty_slot = 1; + } + else { + if (tiw->w[slot] == p) + tiw->w[slot] = p->next; + p->prev->next = p->next; + p->next->prev = p->prev; + empty_slot = 0; + } + if (slot == ERTS_TW_SLOT_AT_ONCE) { + ERTS_TW_ASSERT(tiw->at_once.nto > 0); + tiw->at_once.nto--; + } + else { + scnt_dec(tiw->scnt, slot); + if (slot < ERTS_TW_SOON_WHEEL_END_SLOT) { + if (empty_slot + && tiw->true_next_timeout_time + && p->timeout_pos == tiw->next_timeout_pos) { + tiw->true_next_timeout_time = 0; + } + if (--tiw->soon.nto == 0) + tiw->soon.min_tpos = ERTS_MAX_CLKTCKS; + } + else { + if (empty_slot + && tiw->true_next_timeout_time + && tiw->later.min_tpos_slot == slot) { + ErtsMonotonicTime tpos = tiw->later.min_tpos; + tpos &= ERTS_TW_LATER_WHEEL_POS_MASK; + tpos -= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + if (tpos == tiw->next_timeout_pos) + tiw->true_next_timeout_time = 0; + } + if (--tiw->later.nto == 0) { + tiw->later.min_tpos = ERTS_MAX_CLKTCKS; + tiw->later.min_tpos_slot = ERTS_TW_LATER_WHEEL_END_SLOT; + } + } + } + p->slot = ERTS_TW_SLOT_INACTIVE; } -/* Private export to erl_time_sup.c */ -erts_short_time_t erts_next_time(void) +ErtsMonotonicTime +erts_check_next_timeout_time(ErtsSchedulerData *esdp) { - erts_short_time_t ret; + ErtsTimerWheel *tiw = esdp->timer_wheel; + ErtsMonotonicTime time; + ERTS_MSACC_DECLARE_CACHE_X(); + ERTS_TW_ASSERT(tiw->next_timeout_time + == ERTS_CLKTCKS_TO_MONOTONIC(tiw->next_timeout_pos)); + if (tiw->true_next_timeout_time) + return tiw->next_timeout_time; /* known timeout... */ + if (tiw->next_timeout_pos > tiw->pos + ERTS_TW_SOON_WHEEL_SIZE) + return tiw->next_timeout_time; /* sufficiently later away... */ + ERTS_MSACC_PUSH_AND_SET_STATE_CACHED_X(ERTS_MSACC_STATE_TIMERS); + time = find_next_timeout(esdp, tiw); + ERTS_MSACC_POP_STATE_M_X(); + return time; +} - erts_smp_mtx_lock(&tiw_lock); - (void)do_time_update(); - ret = next_time_internal(); - erts_smp_mtx_unlock(&tiw_lock); - return ret; +static ERTS_INLINE void +timeout_timer(ErtsTWheelTimer *p) +{ + ErlTimeoutProc timeout; + void *arg; + p->slot = ERTS_TW_SLOT_INACTIVE; + timeout = p->timeout; + arg = p->arg; + (*timeout)(arg); + ASSERT_NO_LOCKED_LOCKS; } -static ERTS_INLINE void bump_timer_internal(erts_short_time_t dt) /* PRE: tiw_lock is write-locked */ +void +erts_bump_timers(ErtsTimerWheel *tiw, ErtsMonotonicTime curr_time) { - Uint keep_pos; - Uint count; - ErlTimer *p, **prev, *timeout_head, **timeout_tail; - Uint dtime = (Uint) dt; - - /* no need to bump the position if there aren't any timeouts */ - if (tiw_nto == 0) { - erts_smp_mtx_unlock(&tiw_lock); - return; + int slot, restarted, yield_count, slots, scnt_ix; + ErtsMonotonicTime bump_to; + Sint *scnt, *bump_scnt; + ERTS_MSACC_PUSH_AND_SET_STATE_M_X(ERTS_MSACC_STATE_TIMERS); + + yield_count = ERTS_TWHEEL_BUMP_YIELD_LIMIT; + + scnt = &tiw->scnt[0]; + bump_scnt = &tiw->bump_scnt[0]; + + /* + * In order to be fair we always continue with work + * where we left off when restarting after a yield. + */ + + slot = tiw->yield_slot; + restarted = slot != ERTS_TW_SLOT_INACTIVE; + if (restarted) { + bump_to = tiw->pos; + if (slot >= ERTS_TW_LATER_WHEEL_FIRST_SLOT) + goto restart_yielded_later_slot; + tiw->yield_slot = ERTS_TW_SLOT_INACTIVE; + if (slot == ERTS_TW_SLOT_AT_ONCE) + goto restart_yielded_at_once_slot; + scnt_ix = scnt_get_ix(slot); + slots = tiw->yield_slots_left; + ASSERT(0 <= slots && slots <= ERTS_TW_SOON_WHEEL_SIZE); + goto restart_yielded_soon_slot; } - /* if do_time > TIW_SIZE we want to go around just once */ - count = (Uint)(dtime / TIW_SIZE) + 1; - keep_pos = (tiw_pos + dtime) % TIW_SIZE; - if (dtime > TIW_SIZE) dtime = TIW_SIZE; - - timeout_head = NULL; - timeout_tail = &timeout_head; - while (dtime > 0) { - /* this is to decrease the counters with the right amount */ - /* when dtime >= TIW_SIZE */ - if (tiw_pos == keep_pos) count--; - prev = &tiw[tiw_pos]; - while ((p = *prev) != NULL) { - ASSERT( p != p->next); - if (p->count < count) { /* we have a timeout */ - /* remove min time */ - if (tiw_min_ptr == p) { - tiw_min_ptr = NULL; - tiw_min = 0; - } + do { + + restarted = 0; + bump_to = ERTS_MONOTONIC_TO_CLKTCKS(curr_time); + tiw->true_next_timeout_time = 1; + tiw->next_timeout_pos = bump_to; + tiw->next_timeout_time = ERTS_CLKTCKS_TO_MONOTONIC(bump_to); - /* Remove from list */ - remove_timer(p); - *timeout_tail = p; /* Insert in timeout queue */ - timeout_tail = &p->next; + while (1) { + ErtsTWheelTimer *p; + + if (tiw->nto == 0) { + empty_wheel: + ERTS_TW_DBG_VERIFY_EMPTY_SOON_SLOTS(tiw, bump_to); + ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(tiw, bump_to); + tiw->true_next_timeout_time = 0; + tiw->next_timeout_pos = bump_to + ERTS_CLKTCKS_WEEK; + tiw->next_timeout_time = ERTS_CLKTCKS_TO_MONOTONIC(tiw->next_timeout_pos);; + tiw->pos = bump_to; + tiw->later.pos = bump_to + ERTS_TW_SOON_WHEEL_SIZE; + tiw->later.pos &= ERTS_TW_LATER_WHEEL_POS_MASK; + tiw->yield_slot = ERTS_TW_SLOT_INACTIVE; + ERTS_MSACC_POP_STATE_M_X(); + return; } - else { - /* no timeout, just decrease counter */ - p->count -= count; - prev = &p->next; + + p = tiw->w[ERTS_TW_SLOT_AT_ONCE]; + + if (p) { + + if (p->next == p) { + ERTS_TW_ASSERT(tiw->sentinel.next == &tiw->sentinel); + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + } + else { + tiw->sentinel.next = p->next; + tiw->sentinel.prev = p->prev; + tiw->sentinel.next->prev = &tiw->sentinel; + tiw->sentinel.prev->next = &tiw->sentinel; + } + tiw->w[ERTS_TW_SLOT_AT_ONCE] = NULL; + + while (1) { + ERTS_TW_ASSERT(tiw->nto > 0); + ERTS_TW_ASSERT(tiw->at_once.nto > 0); + tiw->nto--; + tiw->at_once.nto--; + + timeout_timer(p); + + yield_count -= ERTS_TW_COST_TIMEOUT; + + restart_yielded_at_once_slot: + + p = tiw->sentinel.next; + if (p == &tiw->sentinel) { + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + break; + } + + if (yield_count <= 0) { + ERTS_TW_ASSERT(tiw->nto > 0); + ERTS_TW_ASSERT(tiw->at_once.nto > 0); + tiw->yield_slot = ERTS_TW_SLOT_AT_ONCE; + ERTS_MSACC_POP_STATE_M_X(); + return; /* Yield! */ + } + + tiw->sentinel.next = p->next; + p->next->prev = &tiw->sentinel; + } + + } + + if (tiw->pos >= bump_to) { + ERTS_MSACC_POP_STATE_M_X(); + break; + } + + if (tiw->nto == 0) + goto empty_wheel; + + /* + * Save slot counts in bump operation local + * array. + * + * The amount of timers to trigger (or move) + * will only decrease from now until we have + * completed this bump operation (even if we + * yield in the middle of it). + * + * The amount of timers in the wheels may + * however increase due to timers being set + * by timeout callbacks. + */ + sys_memcpy((void *) bump_scnt, (void *) scnt, + sizeof(Sint) * ERTS_TW_SCNT_SIZE); + + if (tiw->soon.min_tpos > tiw->pos) { + ErtsMonotonicTime skip_until_pos = tiw->soon.min_tpos; + + /* + * No need inspecting slots where we know no timeouts + * to trigger should reside. + */ + + if (skip_until_pos > bump_to) + skip_until_pos = bump_to; + + skip_until_pos--; + + if (skip_until_pos > tiw->pos) { + ERTS_TW_DBG_VERIFY_EMPTY_SOON_SLOTS(tiw, skip_until_pos); + tiw->pos = skip_until_pos; + } + } + + { + ErtsMonotonicTime tmp_slots = bump_to - tiw->pos; + tmp_slots = (bump_to - tiw->pos); + if (tmp_slots < ERTS_TW_SOON_WHEEL_SIZE) + slots = (int) tmp_slots; + else + slots = ERTS_TW_SOON_WHEEL_SIZE; + } + + slot = soon_slot(tiw->pos+1); + tiw->pos = bump_to; + + tiw->next_timeout_pos = bump_to; + tiw->next_timeout_time = ERTS_CLKTCKS_TO_MONOTONIC(bump_to); + + scnt_ix = scnt_get_ix(slot); + + /* Timeout timers in soon wheel */ + while (slots > 0) { + + yield_count -= ERTS_TW_COST_SLOT; + + p = tiw->w[slot]; + if (p) { + /* timeout callback need tiw->pos to be up to date */ + if (p->next == p) { + ERTS_TW_ASSERT(tiw->sentinel.next == &tiw->sentinel); + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + } + else { + tiw->sentinel.next = p->next; + tiw->sentinel.prev = p->prev; + tiw->sentinel.next->prev = &tiw->sentinel; + tiw->sentinel.prev->next = &tiw->sentinel; + } + tiw->w[slot] = NULL; + + while (1) { + + ERTS_TW_ASSERT(ERTS_TW_SOON_WHEEL_FIRST_SLOT <= p->slot + && p->slot < ERTS_TW_SOON_WHEEL_END_SLOT); + if (--tiw->soon.nto == 0) + tiw->soon.min_tpos = ERTS_MAX_CLKTCKS; + scnt_ix_dec(scnt, scnt_ix); + if (p->timeout_pos <= bump_to) { + timeout_timer(p); + tiw->nto--; + scnt_ix_dec(bump_scnt, scnt_ix); + yield_count -= ERTS_TW_COST_TIMEOUT; + } + else { + /* uncommon case */ + insert_timer_into_slot(tiw, slot, p); + yield_count -= ERTS_TW_COST_SLOT_MOVE; + } + + restart_yielded_soon_slot: + + p = tiw->sentinel.next; + if (p == &tiw->sentinel) { + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + break; + } + + if (yield_count <= 0) { + tiw->yield_slot = slot; + tiw->yield_slots_left = slots; + ERTS_MSACC_POP_STATE_M_X(); + return; /* Yield! */ + } + + tiw->sentinel.next = p->next; + p->next->prev = &tiw->sentinel; + } + } + + scnt_soon_wheel_next(&slot, &slots, NULL, &scnt_ix, bump_scnt); } + + if (ERTS_TW_BUMP_LATER_WHEEL(tiw)) { + restart_yielded_later_slot: + if (bump_later_wheel(tiw, &yield_count)) + return; /* Yield! */ + } } - tiw_pos = (tiw_pos + 1) % TIW_SIZE; - dtime--; - } - tiw_pos = keep_pos; - if (tiw_min_ptr) - tiw_min -= dt; - - erts_smp_mtx_unlock(&tiw_lock); - - /* Call timedout timers callbacks */ - while (timeout_head) { - p = timeout_head; - timeout_head = p->next; - /* Here comes hairy use of the timer fields! - * They are reset without having the lock. - * It is assumed that no code but this will - * accesses any field until the ->timeout - * callback is called. - */ - p->next = NULL; - p->prev = NULL; - p->slot = 0; - (*p->timeout)(p->arg); - } + + } while (restarted); + + tiw->true_next_timeout_time = 0; + ERTS_TW_ASSERT(tiw->next_timeout_pos == bump_to); + + (void) find_next_timeout(NULL, tiw); + ERTS_MSACC_POP_STATE_M_X(); } -void erts_bump_timer(erts_short_time_t dt) /* dt is value from do_time */ +static int +bump_later_wheel(ErtsTimerWheel *tiw, int *ycount_p) { - erts_smp_mtx_lock(&tiw_lock); - bump_timer_internal(dt); + ErtsMonotonicTime cpos = tiw->pos; + ErtsMonotonicTime later_pos = tiw->later.pos; + int ycount = *ycount_p; + int slots, fslot, scnt_ix; + Sint *scnt, *bump_scnt; + + scnt = &tiw->scnt[0]; + bump_scnt = &tiw->bump_scnt[0]; + + ERTS_HARD_DBG_CHK_WHEELS(tiw, 0); + + if (tiw->yield_slot >= ERTS_TW_LATER_WHEEL_FIRST_SLOT) { + fslot = tiw->yield_slot; + scnt_ix = scnt_get_ix(fslot); + slots = tiw->yield_slots_left; + ASSERT(0 <= slots && slots <= ERTS_TW_LATER_WHEEL_SIZE); + tiw->yield_slot = ERTS_TW_SLOT_INACTIVE; + goto restart_yielded_slot; + } + else { + ErtsMonotonicTime end_later_pos, tmp_slots, min_tpos; + + min_tpos = tiw->later.min_tpos & ERTS_TW_LATER_WHEEL_POS_MASK; + end_later_pos = cpos + ERTS_TW_SOON_WHEEL_SIZE; + end_later_pos &= ERTS_TW_LATER_WHEEL_POS_MASK; + + /* Skip known empty slots... */ + if (min_tpos > later_pos) { + if (min_tpos > end_later_pos) { + ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(tiw, end_later_pos); + tiw->later.pos = end_later_pos; + goto done; + } + later_pos = min_tpos; + ERTS_TW_DBG_VERIFY_EMPTY_LATER_SLOTS(tiw, later_pos); + } + + tmp_slots = end_later_pos; + tmp_slots -= later_pos; + tmp_slots /= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + if (tmp_slots < ERTS_TW_LATER_WHEEL_SIZE) + slots = (int) tmp_slots; + else + slots = ERTS_TW_LATER_WHEEL_SIZE; + + fslot = later_slot(later_pos); + scnt_ix = scnt_get_ix(fslot); + + tiw->later.pos = end_later_pos; + } + + while (slots > 0) { + ErtsTWheelTimer *p; + + ycount -= ERTS_TW_COST_SLOT; + + p = tiw->w[fslot]; + + if (p) { + + if (p->next == p) { + ERTS_TW_ASSERT(tiw->sentinel.next == &tiw->sentinel); + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + } + else { + tiw->sentinel.next = p->next; + tiw->sentinel.prev = p->prev; + tiw->sentinel.next->prev = &tiw->sentinel; + tiw->sentinel.prev->next = &tiw->sentinel; + } + tiw->w[fslot] = NULL; + + while (1) { + ErtsMonotonicTime tpos = p->timeout_pos; + + ERTS_TW_ASSERT(p->slot == fslot); + + if (--tiw->later.nto == 0) { + tiw->later.min_tpos = ERTS_MAX_CLKTCKS; + tiw->later.min_tpos_slot = ERTS_TW_LATER_WHEEL_END_SLOT; + } + scnt_ix_dec(scnt, scnt_ix); + + if (tpos >= tiw->later.pos + ERTS_TW_LATER_WHEEL_SLOT_SIZE) { + /* keep in later slot; very uncommon... */ + insert_timer_into_slot(tiw, fslot, p); + ycount -= ERTS_TW_COST_SLOT_MOVE; + } + else { + scnt_ix_dec(bump_scnt, scnt_ix); + ERTS_TW_ASSERT(tpos < cpos + ERTS_TW_SOON_WHEEL_SIZE); + if (tpos > cpos) { + /* move into soon wheel */ + insert_timer_into_slot(tiw, soon_slot(tpos), p); + ycount -= ERTS_TW_COST_SLOT_MOVE; + } + else { + /* trigger at once */ + timeout_timer(p); + tiw->nto--; + ycount -= ERTS_TW_COST_TIMEOUT; + } + } + + restart_yielded_slot: + + p = tiw->sentinel.next; + if (p == &tiw->sentinel) { + ERTS_TW_ASSERT(tiw->sentinel.prev == &tiw->sentinel); + break; + } + + if (ycount < 0) { + tiw->yield_slot = fslot; + tiw->yield_slots_left = slots; + *ycount_p = 0; + ERTS_HARD_DBG_CHK_WHEELS(tiw, 0); + return 1; /* Yield! */ + } + + tiw->sentinel.next = p->next; + p->next->prev = &tiw->sentinel; + } + } + + scnt_later_wheel_next(&fslot, &slots, NULL, &scnt_ix, bump_scnt); + } + +done: + + ERTS_HARD_DBG_CHK_WHEELS(tiw, 0); + + *ycount_p = ycount; + + return 0; } Uint erts_timer_wheel_memory_size(void) { - return (Uint) TIW_SIZE * sizeof(ErlTimer*); + return sizeof(ErtsTimerWheel)*erts_no_schedulers; +} + +ErtsTimerWheel * +erts_create_timer_wheel(ErtsSchedulerData *esdp) +{ + ErtsMonotonicTime mtime; + int i; + ErtsTimerWheel *tiw; + + /* Some compile time sanity checks... */ + + /* Slots... */ + ERTS_CT_ASSERT(ERTS_TW_SLOT_AT_ONCE == -1); + ERTS_CT_ASSERT(ERTS_TW_SLOT_INACTIVE < ERTS_TW_SLOT_AT_ONCE); + ERTS_CT_ASSERT(ERTS_TW_SLOT_AT_ONCE + 1 == ERTS_TW_SOON_WHEEL_FIRST_SLOT); + ERTS_CT_ASSERT(ERTS_TW_SOON_WHEEL_FIRST_SLOT < ERTS_TW_SOON_WHEEL_END_SLOT); + ERTS_CT_ASSERT(ERTS_TW_SOON_WHEEL_END_SLOT == ERTS_TW_LATER_WHEEL_FIRST_SLOT); + ERTS_CT_ASSERT(ERTS_TW_LATER_WHEEL_FIRST_SLOT < ERTS_TW_LATER_WHEEL_END_SLOT); + + /* Both wheel sizes should be a powers of 2 */ + ERTS_CT_ASSERT(ERTS_TW_SOON_WHEEL_SIZE + && !(ERTS_TW_SOON_WHEEL_SIZE & (ERTS_TW_SOON_WHEEL_SIZE-1))); + ERTS_CT_ASSERT(ERTS_TW_LATER_WHEEL_SIZE + && !(ERTS_TW_LATER_WHEEL_SIZE & (ERTS_TW_LATER_WHEEL_SIZE-1))); + + tiw = erts_alloc_permanent_cache_aligned(ERTS_ALC_T_TIMER_WHEEL, + sizeof(ErtsTimerWheel)); + tiw->w = &tiw->slots[1]; + for(i = ERTS_TW_SLOT_AT_ONCE; i < ERTS_TW_LATER_WHEEL_END_SLOT; i++) + tiw->w[i] = NULL; + + for (i = 0; i < ERTS_TW_SCNT_SIZE; i++) + tiw->scnt[i] = 0; + + mtime = erts_get_monotonic_time(esdp); + tiw->pos = ERTS_MONOTONIC_TO_CLKTCKS(mtime); + tiw->nto = 0; + tiw->at_once.nto = 0; + tiw->soon.min_tpos = ERTS_MAX_CLKTCKS; + tiw->soon.nto = 0; + tiw->later.min_tpos = ERTS_MAX_CLKTCKS; + tiw->later.min_tpos_slot = ERTS_TW_LATER_WHEEL_END_SLOT; + tiw->later.pos = tiw->pos + ERTS_TW_SOON_WHEEL_SIZE; + tiw->later.pos &= ERTS_TW_LATER_WHEEL_POS_MASK; + tiw->later.nto = 0; + tiw->yield_slot = ERTS_TW_SLOT_INACTIVE; + tiw->true_next_timeout_time = 0; + tiw->next_timeout_pos = tiw->pos + ERTS_CLKTCKS_WEEK; + tiw->next_timeout_time = ERTS_CLKTCKS_TO_MONOTONIC(tiw->next_timeout_pos); + tiw->sentinel.next = &tiw->sentinel; + tiw->sentinel.prev = &tiw->sentinel; + tiw->sentinel.timeout = NULL; + tiw->sentinel.arg = NULL; + return tiw; } +ErtsNextTimeoutRef +erts_get_next_timeout_reference(ErtsTimerWheel *tiw) +{ + return (ErtsNextTimeoutRef) &tiw->next_timeout_time; +} + + /* this routine links the time cells into a free list at the start and sets the time queue as empty */ void -erts_init_time(void) +erts_init_time(int time_correction, ErtsTimeWarpMode time_warp_mode) { - int i, itime; + int itime; /* system dependent init; must be done before do_time_init() if timer thread is enabled */ - itime = erts_init_time_sup(); + itime = erts_init_time_sup(time_correction, time_warp_mode); #ifdef TIW_ITIME_IS_CONSTANT if (itime != TIW_ITIME) { - erl_exit(ERTS_ABORT_EXIT, "timer resolution mismatch %d != %d", itime, TIW_ITIME); + erts_exit(ERTS_ABORT_EXIT, "timer resolution mismatch %d != %d", itime, TIW_ITIME); } #else tiw_itime = itime; #endif - - erts_smp_mtx_init(&tiw_lock, "timer_wheel"); - - tiw = (ErlTimer**) erts_alloc(ERTS_ALC_T_TIMER_WHEEL, - TIW_SIZE * sizeof(ErlTimer*)); - for(i = 0; i < TIW_SIZE; i++) - tiw[i] = NULL; - do_time_init(); - tiw_pos = tiw_nto = 0; - tiw_min_ptr = NULL; - tiw_min = 0; } +void +erts_twheel_set_timer(ErtsTimerWheel *tiw, + ErtsTWheelTimer *p, ErlTimeoutProc timeout, + void *arg, ErtsMonotonicTime timeout_pos) +{ + int slot; + ERTS_MSACC_PUSH_AND_SET_STATE_M_X(ERTS_MSACC_STATE_TIMERS); + p->timeout = timeout; + p->arg = arg; + ERTS_TW_ASSERT(p->slot == ERTS_TW_SLOT_INACTIVE); -/* -** Insert a process into the time queue, with a timeout 't' -*/ -static void -insert_timer(ErlTimer* p, Uint t) -{ - Uint tm; - Uint64 ticks; - - /* The current slot (tiw_pos) in timing wheel is the next slot to be - * be processed. Hence no extra time tick is needed. - * - * (x + y - 1)/y is precisely the "number of bins" formula. - */ - ticks = (t + (TIW_ITIME - 1)) / TIW_ITIME; + tiw->nto++; - /* - * Ticks must be a Uint64, or the addition may overflow here, - * resulting in an incorrect value for p->count below. - */ - ticks += do_time_update(); /* Add backlog of unprocessed time */ - /* calculate slot */ - tm = (ticks + tiw_pos) % TIW_SIZE; - p->slot = (Uint) tm; - p->count = (Uint) (ticks / TIW_SIZE); - - /* insert at head of list at slot */ - p->next = tiw[tm]; - p->prev = NULL; - if (p->next != NULL) - p->next->prev = p; - tiw[tm] = p; - - - /* insert min time */ - if ((tiw_nto == 0) || ((tiw_min_ptr != NULL) && (ticks < tiw_min))) { - tiw_min = ticks; - tiw_min_ptr = p; + if (timeout_pos <= tiw->pos) { + /* at once */ + p->timeout_pos = timeout_pos = tiw->pos; + slot = ERTS_TW_SLOT_AT_ONCE; } - if ((tiw_min_ptr == p) && (ticks > tiw_min)) { - /* some other timer might be 'min' now */ - tiw_min = 0; - tiw_min_ptr = NULL; + else if (timeout_pos < tiw->pos + ERTS_TW_SOON_WHEEL_SIZE) { + /* soon wheel */ + p->timeout_pos = timeout_pos; + slot = soon_slot(timeout_pos); + if (tiw->soon.min_tpos > timeout_pos) + tiw->soon.min_tpos = timeout_pos; + } + else { + /* later wheel */ + p->timeout_pos = timeout_pos; + slot = later_slot(timeout_pos); + + /* + * Next timeout due to this timeout + * should be in good time before the + * actual timeout (one later wheel slot + * size). This, in order to move it + * from the later wheel to the soon + * wheel. + */ + timeout_pos &= ERTS_TW_LATER_WHEEL_POS_MASK; + timeout_pos -= ERTS_TW_LATER_WHEEL_SLOT_SIZE; } - tiw_nto++; + insert_timer_into_slot(tiw, slot, p); + + if (timeout_pos <= tiw->next_timeout_pos) { + tiw->true_next_timeout_time = 1; + if (timeout_pos < tiw->next_timeout_pos) { + tiw->next_timeout_pos = timeout_pos; + tiw->next_timeout_time = ERTS_CLKTCKS_TO_MONOTONIC(timeout_pos); + } + } + ERTS_MSACC_POP_STATE_M_X(); } void -erts_set_timer(ErlTimer* p, ErlTimeoutProc timeout, ErlCancelProc cancel, - void* arg, Uint t) +erts_twheel_cancel_timer(ErtsTimerWheel *tiw, ErtsTWheelTimer *p) { - - erts_deliver_time(); - erts_smp_mtx_lock(&tiw_lock); - if (p->active) { /* XXX assert ? */ - erts_smp_mtx_unlock(&tiw_lock); - return; + if (p->slot != ERTS_TW_SLOT_INACTIVE) { + ERTS_MSACC_PUSH_AND_SET_STATE_M_X(ERTS_MSACC_STATE_TIMERS); + remove_timer(tiw, p); + tiw->nto--; + ERTS_MSACC_POP_STATE_M_X(); } - p->timeout = timeout; - p->cancel = cancel; - p->arg = arg; - p->active = 1; - insert_timer(p, t); - erts_smp_mtx_unlock(&tiw_lock); -#if defined(ERTS_SMP) - if (t <= (Uint) ERTS_SHORT_TIME_T_MAX) - erts_sys_schedule_interrupt_timed(1, (erts_short_time_t) t); -#endif } void -erts_cancel_timer(ErlTimer* p) +erts_twheel_debug_foreach(ErtsTimerWheel *tiw, + void (*tclbk)(void *), + void (*func)(void *, + ErtsMonotonicTime, + void *), + void *arg) { - erts_smp_mtx_lock(&tiw_lock); - if (!p->active) { /* allow repeated cancel (drivers) */ - erts_smp_mtx_unlock(&tiw_lock); - return; - } + ErtsTWheelTimer *tmr; + int ix; - /* is it the 'min' timer, remove min */ - if (p == tiw_min_ptr) { - tiw_min_ptr = NULL; - tiw_min = 0; + tmr = tiw->sentinel.next; + while (tmr != &tiw->sentinel) { + if (tmr->timeout == tclbk) + (*func)(arg, tmr->timeout_pos, tmr->arg); + tmr = tmr->next; } - remove_timer(p); - p->slot = p->count = 0; - - if (p->cancel != NULL) { - erts_smp_mtx_unlock(&tiw_lock); - (*p->cancel)(p->arg); - return; + for (ix = ERTS_TW_SLOT_AT_ONCE; ix < ERTS_TW_LATER_WHEEL_END_SLOT; ix++) { + tmr = tiw->w[ix]; + if (tmr) { + do { + if (tmr->timeout == tclbk) + (*func)(arg, tmr->timeout_pos, tmr->arg); + tmr = tmr->next; + } while (tmr != tiw->w[ix]); + } } - erts_smp_mtx_unlock(&tiw_lock); } -/* - Returns the amount of time left in ms until the timer 'p' is triggered. - 0 is returned if 'p' isn't active. - 0 is returned also if the timer is overdue (i.e., would have triggered - immediately if it hadn't been cancelled). -*/ -Uint -erts_time_left(ErlTimer *p) +#ifdef ERTS_TW_DEBUG + +void +dbg_verify_empty_soon_slots(ErtsTimerWheel *tiw, ErtsMonotonicTime to_pos) { - Uint left; - erts_short_time_t dt; + int ix; + ErtsMonotonicTime tmp; - erts_smp_mtx_lock(&tiw_lock); + ix = soon_slot(tiw->pos); + tmp = to_pos; + if (tmp > tiw->pos) { + int slots; + tmp -= tiw->pos; + ERTS_TW_ASSERT(tmp > 0); + if (tmp < (ErtsMonotonicTime) ERTS_TW_SOON_WHEEL_SIZE) + slots = (int) tmp; + else + slots = ERTS_TW_SOON_WHEEL_SIZE; - if (!p->active) { - erts_smp_mtx_unlock(&tiw_lock); - return 0; - } + while (slots > 0) { + ERTS_TW_ASSERT(!tiw->w[ix]); + ix++; + if (ix == ERTS_TW_SOON_WHEEL_END_SLOT) + ix = ERTS_TW_SOON_WHEEL_FIRST_SLOT; + slots--; + } + } +} + +void +dbg_verify_empty_later_slots(ErtsTimerWheel *tiw, ErtsMonotonicTime to_pos) +{ + int ix; + ErtsMonotonicTime tmp; + + ix = later_slot(tiw->later.pos); + tmp = to_pos; + tmp &= ERTS_TW_LATER_WHEEL_POS_MASK; + if (tmp > tiw->later.pos) { + ErtsMonotonicTime pos_min; + int slots; + tmp -= tiw->later.pos; + tmp /= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + ERTS_TW_ASSERT(tmp > 0); - if (p->slot < tiw_pos) - left = (p->count + 1) * TIW_SIZE + p->slot - tiw_pos; - else - left = p->count * TIW_SIZE + p->slot - tiw_pos; - dt = do_time_read(); - if (left < dt) - left = 0; - else - left -= dt; + pos_min = tiw->later.pos; - erts_smp_mtx_unlock(&tiw_lock); + if (tmp < (ErtsMonotonicTime) ERTS_TW_LATER_WHEEL_SIZE) + slots = (int) tmp; + else { + pos_min += ((tmp / ERTS_TW_LATER_WHEEL_SIZE) + * ERTS_TW_LATER_WHEEL_SLOT_SIZE); + slots = ERTS_TW_LATER_WHEEL_SIZE; + } - return (Uint) left * TIW_ITIME; + while (slots > 0) { + ErtsTWheelTimer *tmr = tiw->w[ix]; + pos_min += ERTS_TW_LATER_WHEEL_SLOT_SIZE; + if (tmr) { + ErtsTWheelTimer *end = tmr; + do { + ERTS_TW_ASSERT(tmr->timeout_pos >= pos_min); + tmr = tmr->next; + } while (tmr != end); + } + ix++; + if (ix == ERTS_TW_LATER_WHEEL_END_SLOT) + ix = ERTS_TW_LATER_WHEEL_FIRST_SLOT; + slots--; + } + } } -#ifdef DEBUG -void erts_p_slpq(void) +#endif /* ERTS_TW_DEBUG */ + +#ifdef ERTS_TW_HARD_DEBUG + +static void +hrd_dbg_check_wheels(ErtsTimerWheel *tiw, int check_min_tpos) { - int i; - ErlTimer* p; - - erts_smp_mtx_lock(&tiw_lock); - - /* print the whole wheel, starting at the current position */ - erts_printf("\ntiw_pos = %d tiw_nto %d\n", tiw_pos, tiw_nto); - i = tiw_pos; - if (tiw[i] != NULL) { - erts_printf("%d:\n", i); - for(p = tiw[i]; p != NULL; p = p->next) { - erts_printf(" (count %d, slot %d)\n", - p->count, p->slot); - } + int ix, six, soon_tmo, later_tmo, at_once_tmo, + scnt_slot, scnt_slots, scnt_six; + ErtsMonotonicTime min_tpos; + Sint scnt[ERTS_TW_SCNT_SIZE]; + ErtsTWheelTimer *p; + + for (six = 0; six < ERTS_TW_SCNT_SIZE; six++) + scnt[six] = 0; + + min_tpos = ERTS_MONOTONIC_TO_CLKTCKS(tiw->next_timeout_time); + + at_once_tmo = 0; + p = tiw->w[ERTS_TW_SLOT_AT_ONCE]; + if (p) { + ErtsTWheelTimer *first = p; + do { + at_once_tmo++; + ERTS_TW_ASSERT(p->slot == ERTS_TW_SLOT_AT_ONCE); + ERTS_TW_ASSERT(p->timeout_pos <= tiw->pos); + ERTS_TW_ASSERT(!check_min_tpos || tiw->pos >= min_tpos); + ERTS_TW_ASSERT(p->next->prev == p); + p = p->next; + } while (p != first); } - for(i = (i+1)%TIW_SIZE; i != tiw_pos; i = (i+1)%TIW_SIZE) { - if (tiw[i] != NULL) { - erts_printf("%d:\n", i); - for(p = tiw[i]; p != NULL; p = p->next) { - erts_printf(" (count %d, slot %d)\n", - p->count, p->slot); - } - } + + soon_tmo = 0; + scnt_slot = ERTS_TW_SOON_WHEEL_END_SLOT-1; + scnt_slots = ERTS_TW_SOON_WHEEL_SIZE; + scnt_six = 0; + scnt_soon_wheel_next(&scnt_slot, &scnt_slots, + NULL, &scnt_six, tiw->scnt); + for (ix = ERTS_TW_SOON_WHEEL_FIRST_SLOT; + ix < ERTS_TW_SOON_WHEEL_END_SLOT; + ix++) { + p = tiw->w[ix]; + six = scnt_get_ix(ix); + ERTS_TW_ASSERT(!p || six == scnt_six); + if (p) { + ErtsTWheelTimer *first = p; + do { + ErtsMonotonicTime tpos = p->timeout_pos; + soon_tmo++; + scnt_ix_inc(scnt, six); + ERTS_TW_ASSERT(p->slot == ix); + ERTS_TW_ASSERT(ix == soon_slot(tpos)); + ERTS_TW_ASSERT(p->timeout_pos < tiw->pos + ERTS_TW_SOON_WHEEL_SIZE); + ERTS_TW_ASSERT(!check_min_tpos || tpos >= min_tpos); + ERTS_TW_ASSERT(p->next->prev == p); + p = p->next; + } while (p != first); + } + if (ix == scnt_slot) + scnt_soon_wheel_next(&scnt_slot, &scnt_slots, + NULL, &scnt_six, tiw->scnt); } - erts_smp_mtx_unlock(&tiw_lock); + later_tmo = 0; + scnt_slot = ERTS_TW_SOON_WHEEL_END_SLOT-1; + scnt_slots = ERTS_TW_SOON_WHEEL_SIZE; + scnt_six = 0; + scnt_later_wheel_next(&scnt_slot, &scnt_slots, + NULL, &scnt_six, tiw->scnt); + for (ix = ERTS_TW_LATER_WHEEL_FIRST_SLOT; + ix < ERTS_TW_LATER_WHEEL_END_SLOT; + ix++) { + p = tiw->w[ix]; + six = scnt_get_ix(ix); + ERTS_TW_ASSERT(!p || six == scnt_six); + if (p) { + ErtsTWheelTimer *first = p; + six = scnt_get_ix(ix); + do { + ErtsMonotonicTime tpos = p->timeout_pos; + later_tmo++; + scnt_ix_inc(scnt, six); + ERTS_TW_ASSERT(p->slot == ix); + ERTS_TW_ASSERT(later_slot(tpos) == ix); + tpos &= ERTS_TW_LATER_WHEEL_POS_MASK; + tpos -= ERTS_TW_LATER_WHEEL_SLOT_SIZE; + ERTS_TW_ASSERT(!check_min_tpos || tpos >= min_tpos); + ERTS_TW_ASSERT(p->next->prev == p); + p = p->next; + } while (p != first); + } + if (ix == scnt_slot) + scnt_later_wheel_next(&scnt_slot, &scnt_slots, + NULL, &scnt_six, tiw->scnt); + } + + if (tiw->yield_slot != ERTS_TW_SLOT_INACTIVE) { + p = tiw->sentinel.next; + ix = tiw->yield_slot; + while (p != &tiw->sentinel) { + ErtsMonotonicTime tpos = p->timeout_pos; + ERTS_TW_ASSERT(ix == p->slot); + if (ix == ERTS_TW_SLOT_AT_ONCE) + at_once_tmo++; + else { + scnt_inc(scnt, ix); + if (ix >= ERTS_TW_LATER_WHEEL_FIRST_SLOT) { + later_tmo++; + ERTS_TW_ASSERT(ix == later_slot(tpos)); + } + else { + soon_tmo++; + ERTS_TW_ASSERT(ix == (tpos & ERTS_TW_SOON_WHEEL_MASK)); + ERTS_TW_ASSERT(tpos < tiw->pos + ERTS_TW_SOON_WHEEL_SIZE); + } + p = p->next; + } + } + } + + + ERTS_TW_ASSERT(tiw->at_once.nto == at_once_tmo); + ERTS_TW_ASSERT(tiw->soon.nto == soon_tmo); + ERTS_TW_ASSERT(tiw->later.nto == later_tmo); + ERTS_TW_ASSERT(tiw->nto == soon_tmo + later_tmo + at_once_tmo); + + for (six = 0; six < ERTS_TW_SCNT_SIZE; six++) + ERTS_TW_ASSERT(scnt[six] == tiw->scnt[six]); } -#endif /* DEBUG */ + +#endif /* ERTS_TW_HARD_DEBUG */ |