From: Intel Date: Wed, 18 Sep 2013 10:00:00 +0000 (+0200) Subject: timer: use a skip list X-Git-Tag: spdx-start~11151 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=9b15ba89;p=dpdk.git timer: use a skip list The skip list algorithm allows to improve the scalability. Signed-off-by: Intel --- diff --git a/lib/librte_timer/rte_timer.c b/lib/librte_timer/rte_timer.c old mode 100644 new mode 100755 index eea6d97354..c96693ab79 --- a/lib/librte_timer/rte_timer.c +++ b/lib/librte_timer/rte_timer.c @@ -34,7 +34,6 @@ #include #include #include -#include #include #include @@ -50,21 +49,23 @@ #include #include #include +#include #include "rte_timer.h" LIST_HEAD(rte_timer_list, rte_timer); struct priv_timer { - struct rte_timer_list pending; /**< list of pending timers */ - struct rte_timer_list expired; /**< list of expired timers */ - struct rte_timer_list done; /**< list of done timers */ + struct rte_timer pending_head; /**< dummy timer instance to head up list */ rte_spinlock_t list_lock; /**< lock to protect list access */ /** per-core variable that true if a timer was updated on this * core since last reset of the variable */ int updated; + /** track the current depth of the skiplist */ + unsigned curr_skiplist_depth; + unsigned prev_lcore; /**< used for lcore round robin */ #ifdef RTE_LIBRTE_TIMER_DEBUG @@ -86,25 +87,16 @@ static struct priv_timer priv_timer[RTE_MAX_LCORE]; #define __TIMER_STAT_ADD(name, n) do {} while(0) #endif -/* this macro allow to modify var while browsing the list */ -#define LIST_FOREACH_SAFE(var, var2, head, field) \ - for ((var) = ((head)->lh_first), \ - (var2) = ((var) ? ((var)->field.le_next) : NULL); \ - (var); \ - (var) = (var2), \ - (var2) = ((var) ? ((var)->field.le_next) : NULL)) - - /* Init the timer library. */ void rte_timer_subsystem_init(void) { unsigned lcore_id; + /* since priv_timer is static, it's zeroed by default, so only init some + * fields. + */ for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id ++) { - LIST_INIT(&priv_timer[lcore_id].pending); - LIST_INIT(&priv_timer[lcore_id].expired); - LIST_INIT(&priv_timer[lcore_id].done); rte_spinlock_init(&priv_timer[lcore_id].list_lock); priv_timer[lcore_id].prev_lcore = lcore_id; } @@ -137,7 +129,7 @@ timer_set_config_state(struct rte_timer *tim, lcore_id = rte_lcore_id(); /* wait that the timer is in correct status before update, - * and mark it as beeing configured */ + * and mark it as being configured */ while (success == 0) { prev_status.u32 = tim->status.u32; @@ -146,12 +138,12 @@ timer_set_config_state(struct rte_timer *tim, (unsigned)prev_status.owner != lcore_id) return -1; - /* timer is beeing configured on another core */ + /* timer is being configured on another core */ if (prev_status.state == RTE_TIMER_CONFIG) return -1; /* here, we know that timer is stopped or pending, - * mark it atomically as beeing configured */ + * mark it atomically as being configured */ status.state = RTE_TIMER_CONFIG; status.owner = (int16_t)lcore_id; success = rte_atomic32_cmpset(&tim->status.u32, @@ -194,6 +186,83 @@ timer_set_running_state(struct rte_timer *tim) return 0; } +/* + * Return a skiplist level for a new entry. + * This probabalistically gives a level with p=1/4 that an entry at level n + * will also appear at level n+1. + */ +static uint32_t +timer_get_skiplist_level(unsigned curr_depth) +{ +#ifdef RTE_LIBRTE_TIMER_DEBUG + static uint32_t i, count = 0; + static uint32_t levels[MAX_SKIPLIST_DEPTH] = {0}; +#endif + + /* probability value is 1/4, i.e. all at level 0, 1 in 4 is at level 1, + * 1 in 16 at level 2, 1 in 64 at level 3, etc. Calculated using lowest + * bit position of a (pseudo)random number. + */ + uint32_t rand = rte_rand() & (UINT32_MAX - 1); + uint32_t level = rand == 0 ? MAX_SKIPLIST_DEPTH : (rte_bsf32(rand)-1) / 2; + + /* limit the levels used to one above our current level, so we don't, + * for instance, have a level 0 and a level 7 without anything between + */ + if (level > curr_depth) + level = curr_depth; + if (level >= MAX_SKIPLIST_DEPTH) + level = MAX_SKIPLIST_DEPTH-1; +#ifdef RTE_LIBRTE_TIMER_DEBUG + count ++; + levels[level]++; + if (count % 10000 == 0) + for (i = 0; i < MAX_SKIPLIST_DEPTH; i++) + printf("Level %u: %u\n", (unsigned)i, (unsigned)levels[i]); +#endif + return level; +} + +/* + * For a given time value, get the entries at each level which + * are <= that time value. + */ +static void +timer_get_prev_entries(uint64_t time_val, unsigned tim_lcore, + struct rte_timer **prev) +{ + unsigned lvl = priv_timer[tim_lcore].curr_skiplist_depth; + prev[lvl] = &priv_timer[tim_lcore].pending_head; + while(lvl != 0) { + lvl--; + prev[lvl] = prev[lvl+1]; + while (prev[lvl]->sl_next[lvl] && + prev[lvl]->sl_next[lvl]->expire <= time_val) + prev[lvl] = prev[lvl]->sl_next[lvl]; + } +} + +/* + * Given a timer node in the skiplist, find the previous entries for it at + * all skiplist levels. + */ +static void +timer_get_prev_entries_for_node(struct rte_timer *tim, unsigned tim_lcore, + struct rte_timer **prev) +{ + int i; + /* to get a specific entry in the list, look for just lower than the time + * values, and then increment on each level individually if necessary + */ + timer_get_prev_entries(tim->expire - 1, tim_lcore, prev); + for (i = priv_timer[tim_lcore].curr_skiplist_depth - 1; i >= 0; i--) { + while (prev[i]->sl_next[i] != NULL && + prev[i]->sl_next[i] != tim && + prev[i]->sl_next[i]->expire <= tim->expire) + prev[i] = prev[i]->sl_next[i]; + } +} + /* * add in list, lock if needed * timer must be in config state @@ -202,9 +271,9 @@ timer_set_running_state(struct rte_timer *tim) static void timer_add(struct rte_timer *tim, unsigned tim_lcore, int local_is_locked) { - uint64_t cur_time = rte_get_timer_cycles(); unsigned lcore_id = rte_lcore_id(); - struct rte_timer *t, *t_prev; + unsigned lvl; + struct rte_timer *prev[MAX_SKIPLIST_DEPTH+1]; /* if timer needs to be scheduled on another core, we need to * lock the list; if it is on local core, we need to lock if @@ -212,30 +281,29 @@ timer_add(struct rte_timer *tim, unsigned tim_lcore, int local_is_locked) if (tim_lcore != lcore_id || !local_is_locked) rte_spinlock_lock(&priv_timer[tim_lcore].list_lock); - t = LIST_FIRST(&priv_timer[tim_lcore].pending); - - /* list is empty or 'tim' will expire before 't' */ - if (t == NULL || ((int64_t)(tim->expire - cur_time) < - (int64_t)(t->expire - cur_time))) { - LIST_INSERT_HEAD(&priv_timer[tim_lcore].pending, tim, next); + /* find where exactly this element goes in the list of elements + * for each depth. */ + timer_get_prev_entries(tim->expire, tim_lcore, prev); + + /* now assign it a new level and add at that level */ + const unsigned tim_level = timer_get_skiplist_level( + priv_timer[tim_lcore].curr_skiplist_depth); + if (tim_level == priv_timer[tim_lcore].curr_skiplist_depth) + priv_timer[tim_lcore].curr_skiplist_depth++; + + lvl = tim_level; + while (lvl > 0) { + tim->sl_next[lvl] = prev[lvl]->sl_next[lvl]; + prev[lvl]->sl_next[lvl] = tim; + lvl--; } - else { - t_prev = t; - - /* find an element that will expire after 'tim' */ - LIST_FOREACH(t, &priv_timer[tim_lcore].pending, next) { - if ((int64_t)(tim->expire - cur_time) < - (int64_t)(t->expire - cur_time)) { - LIST_INSERT_BEFORE(t, tim, next); - break; - } - t_prev = t; - } + tim->sl_next[0] = prev[0]->sl_next[0]; + prev[0]->sl_next[0] = tim; - /* not found, insert at the end of the list */ - if (t == NULL) - LIST_INSERT_AFTER(t_prev, tim, next); - } + /* save the lowest list entry into the expire field of the dummy hdr + * NOTE: this is not atomic on 32-bit*/ + priv_timer[tim_lcore].pending_head.expire = priv_timer[tim_lcore].\ + pending_head.sl_next[0]->expire; if (tim_lcore != lcore_id || !local_is_locked) rte_spinlock_unlock(&priv_timer[tim_lcore].list_lock); @@ -247,9 +315,13 @@ timer_add(struct rte_timer *tim, unsigned tim_lcore, int local_is_locked) * timer must be in a list */ static void -timer_del(struct rte_timer *tim, unsigned prev_owner, int local_is_locked) +timer_del(struct rte_timer *tim, union rte_timer_status prev_status, + int local_is_locked) { unsigned lcore_id = rte_lcore_id(); + unsigned prev_owner = prev_status.owner; + int i; + struct rte_timer *prev[MAX_SKIPLIST_DEPTH+1]; /* if timer needs is pending another core, we need to lock the * list; if it is on local core, we need to lock if we are not @@ -257,7 +329,25 @@ timer_del(struct rte_timer *tim, unsigned prev_owner, int local_is_locked) if (prev_owner != lcore_id || !local_is_locked) rte_spinlock_lock(&priv_timer[prev_owner].list_lock); - LIST_REMOVE(tim, next); + /* save the lowest list entry into the expire field of the dummy hdr. + * NOTE: this is not atomic on 32-bit */ + if (tim == priv_timer[prev_owner].pending_head.sl_next[0]) + priv_timer[prev_owner].pending_head.expire = + ((tim->sl_next[0] == NULL) ? 0 : tim->sl_next[0]->expire); + + /* adjust pointers from previous entries to point past this */ + timer_get_prev_entries_for_node(tim, prev_owner, prev); + for (i = priv_timer[prev_owner].curr_skiplist_depth - 1; i >= 0; i--) { + if (prev[i]->sl_next[i] == tim) + prev[i]->sl_next[i] = tim->sl_next[i]; + } + + /* in case we deleted last entry at a level, adjust down max level */ + for (i = priv_timer[prev_owner].curr_skiplist_depth - 1; i >= 0; i--) + if (priv_timer[prev_owner].pending_head.sl_next[i] == NULL) + priv_timer[prev_owner].curr_skiplist_depth --; + else + break; if (prev_owner != lcore_id || !local_is_locked) rte_spinlock_unlock(&priv_timer[prev_owner].list_lock); @@ -282,7 +372,7 @@ __rte_timer_reset(struct rte_timer *tim, uint64_t expire, } /* wait that the timer is in correct status before update, - * and mark it as beeing configured */ + * and mark it as being configured */ ret = timer_set_config_state(tim, &prev_status); if (ret < 0) return -1; @@ -291,9 +381,8 @@ __rte_timer_reset(struct rte_timer *tim, uint64_t expire, priv_timer[lcore_id].updated = 1; /* remove it from list */ - if (prev_status.state == RTE_TIMER_PENDING || - prev_status.state == RTE_TIMER_RUNNING) { - timer_del(tim, prev_status.owner, local_is_locked); + if (prev_status.state == RTE_TIMER_PENDING) { + timer_del(tim, prev_status, local_is_locked); __TIMER_STAT_ADD(pending, -1); } @@ -358,7 +447,7 @@ rte_timer_stop(struct rte_timer *tim) int ret; /* wait that the timer is in correct status before update, - * and mark it as beeing configured */ + * and mark it as being configured */ ret = timer_set_config_state(tim, &prev_status); if (ret < 0) return -1; @@ -367,9 +456,8 @@ rte_timer_stop(struct rte_timer *tim) priv_timer[lcore_id].updated = 1; /* remove it from list */ - if (prev_status.state == RTE_TIMER_PENDING || - prev_status.state == RTE_TIMER_RUNNING) { - timer_del(tim, prev_status.owner, 0); + if (prev_status.state == RTE_TIMER_PENDING) { + timer_del(tim, prev_status, 0); __TIMER_STAT_ADD(pending, -1); } @@ -401,37 +489,52 @@ rte_timer_pending(struct rte_timer *tim) void rte_timer_manage(void) { union rte_timer_status status; - struct rte_timer *tim, *tim2; + struct rte_timer *tim, *next_tim; unsigned lcore_id = rte_lcore_id(); + struct rte_timer *prev[MAX_SKIPLIST_DEPTH + 1]; uint64_t cur_time; - int ret; + int i, ret; __TIMER_STAT_ADD(manage, 1); /* optimize for the case where per-cpu list is empty */ - if (LIST_EMPTY(&priv_timer[lcore_id].pending)) + if (priv_timer[lcore_id].pending_head.sl_next[0] == NULL) return; cur_time = rte_get_timer_cycles(); +#ifdef RTE_ARCH_X86_64 + /* on 64-bit the value cached in the pending_head.expired will be updated + * atomically, so we can consult that for a quick check here outside the + * lock */ + if (likely(priv_timer[lcore_id].pending_head.expire > cur_time)) + return; +#endif + /* browse ordered list, add expired timers in 'expired' list */ rte_spinlock_lock(&priv_timer[lcore_id].list_lock); - LIST_FOREACH_SAFE(tim, tim2, &priv_timer[lcore_id].pending, next) { - if ((int64_t)(cur_time - tim->expire) < 0) - break; - - LIST_REMOVE(tim, next); - LIST_INSERT_HEAD(&priv_timer[lcore_id].expired, tim, next); + /* if nothing to do just unlock and return */ + if (priv_timer[lcore_id].pending_head.sl_next[0] == NULL || + priv_timer[lcore_id].pending_head.sl_next[0]->expire > cur_time) + goto done; + + /* save start of list of expired timers */ + tim = priv_timer[lcore_id].pending_head.sl_next[0]; + + /* break the existing list at current time point */ + timer_get_prev_entries(cur_time, lcore_id, prev); + for (i = priv_timer[lcore_id].curr_skiplist_depth -1; i >= 0; i--) { + priv_timer[lcore_id].pending_head.sl_next[i] = prev[i]->sl_next[i]; + if (prev[i]->sl_next[i] == NULL) + priv_timer[lcore_id].curr_skiplist_depth--; + prev[i] ->sl_next[i] = NULL; } + /* now scan expired list and call callbacks */ + for ( ; tim != NULL; tim = next_tim) { + next_tim = tim->sl_next[0]; - /* for each timer of 'expired' list, check state and execute callback */ - while ((tim = LIST_FIRST(&priv_timer[lcore_id].expired)) != NULL) { ret = timer_set_running_state(tim); - /* remove from expired list, and add it in done list */ - LIST_REMOVE(tim, next); - LIST_INSERT_HEAD(&priv_timer[lcore_id].done, tim, next); - /* this timer was not pending, continue */ if (ret < 0) continue; @@ -452,7 +555,6 @@ void rte_timer_manage(void) if (tim->period == 0) { /* remove from done list and mark timer as stopped */ - LIST_REMOVE(tim, next); __TIMER_STAT_ADD(pending, -1); status.state = RTE_TIMER_STOP; status.owner = RTE_TIMER_NO_OWNER; @@ -460,26 +562,21 @@ void rte_timer_manage(void) tim->status.u32 = status.u32; } else { - /* keep it in done list and mark timer as pending */ + /* keep it in list and mark timer as pending */ status.state = RTE_TIMER_PENDING; status.owner = (int16_t)lcore_id; rte_wmb(); tim->status.u32 = status.u32; + __rte_timer_reset(tim, cur_time + tim->period, + tim->period, lcore_id, tim->f, tim->arg, 1); } } - /* finally, browse done list, some timer may have to be - * rescheduled automatically */ - LIST_FOREACH_SAFE(tim, tim2, &priv_timer[lcore_id].done, next) { - - /* reset may fail if timer is beeing modified, in this - * case the timer will remain in 'done' list until the - * core that is modifying it remove it */ - __rte_timer_reset(tim, cur_time + tim->period, - tim->period, lcore_id, tim->f, - tim->arg, 1); - } - + /* update the next to expire timer value */ + priv_timer[lcore_id].pending_head.expire = + (priv_timer[lcore_id].pending_head.sl_next[0] == NULL) ? 0 : + priv_timer[lcore_id].pending_head.sl_next[0]->expire; +done: /* job finished, unlock the list lock */ rte_spinlock_unlock(&priv_timer[lcore_id].list_lock); } diff --git a/lib/librte_timer/rte_timer.h b/lib/librte_timer/rte_timer.h old mode 100644 new mode 100755 index 07a693b805..803c996922 --- a/lib/librte_timer/rte_timer.h +++ b/lib/librte_timer/rte_timer.h @@ -65,7 +65,6 @@ #include #include -#include #ifdef __cplusplus extern "C" { @@ -117,15 +116,17 @@ struct rte_timer; */ typedef void (rte_timer_cb_t)(struct rte_timer *, void *); +#define MAX_SKIPLIST_DEPTH 10 + /** * A structure describing a timer in RTE. */ struct rte_timer { - LIST_ENTRY(rte_timer) next; /**< Next and prev in list. */ + uint64_t expire; /**< Time when timer expire. */ + struct rte_timer *sl_next[MAX_SKIPLIST_DEPTH]; volatile union rte_timer_status status; /**< Status of timer. */ uint64_t period; /**< Period of timer (0 if not periodic). */ - uint64_t expire; /**< Time when timer expire. */ rte_timer_cb_t *f; /**< Callback function. */ void *arg; /**< Argument to callback function. */ }; @@ -135,10 +136,10 @@ struct rte_timer /** * A C++ static initializer for a timer structure. */ -#define RTE_TIMER_INITIALIZER { \ - {0, 0}, \ - {{RTE_TIMER_STOP, RTE_TIMER_NO_OWNER}}, \ +#define RTE_TIMER_INITIALIZER { \ 0, \ + {NULL}, \ + {{RTE_TIMER_STOP, RTE_TIMER_NO_OWNER}}, \ 0, \ NULL, \ NULL, \