diff options
| -rw-r--r-- | src/core/lib/iomgr/timer_generic.cc | 16 | ||||
| -rw-r--r-- | src/core/lib/iomgr/timer_heap.cc | 4 | ||||
| -rw-r--r-- | src/core/lib/iomgr/timer_heap.h | 6 | ||||
| -rw-r--r-- | src/core/lib/iomgr/timer_manager.cc | 8 | ||||
| -rw-r--r-- | src/core/lib/iomgr/timer_manager.h | 4 |
5 files changed, 20 insertions, 18 deletions
diff --git a/src/core/lib/iomgr/timer_generic.cc b/src/core/lib/iomgr/timer_generic.cc index aba5539199..6a925add80 100644 --- a/src/core/lib/iomgr/timer_generic.cc +++ b/src/core/lib/iomgr/timer_generic.cc @@ -48,22 +48,22 @@ grpc_core::TraceFlag grpc_timer_trace(false, "timer"); grpc_core::TraceFlag grpc_timer_check_trace(false, "timer_check"); /* A "timer shard". Contains a 'heap' and a 'list' of timers. All timers with - * deadlines earlier than 'queue_deadline" cap are maintained in the heap and + * deadlines earlier than 'queue_deadline_cap' are maintained in the heap and * others are maintained in the list (unordered). This helps to keep the number * of elements in the heap low. * * The 'queue_deadline_cap' gets recomputed periodically based on the timer * stats maintained in 'stats' and the relevant timers are then moved from the - * 'list' to 'heap' + * 'list' to 'heap'. */ typedef struct { gpr_mu mu; grpc_time_averaged_stats stats; - /* All and only timers with deadlines <= this will be in the heap. */ + /* All and only timers with deadlines < this will be in the heap. */ grpc_millis queue_deadline_cap; - /* The deadline of the next timer due in this shard */ + /* The deadline of the next timer due in this shard. */ grpc_millis min_deadline; - /* Index of this timer_shard in the g_shard_queue */ + /* Index of this timer_shard in the g_shard_queue. */ uint32_t shard_queue_index; /* This holds all timers with deadlines < queue_deadline_cap. Timers in this list have the top bit of their deadline set to 0. */ @@ -85,7 +85,7 @@ static timer_shard** g_shard_queue; #ifndef NDEBUG -/* == Hash table for duplicate timer detection == */ +/* == DEBUG ONLY: hash table for duplicate timer detection == */ #define NUM_HASH_BUCKETS 1009 /* Prime number close to 1000 */ @@ -177,7 +177,7 @@ static void remove_from_ht(grpc_timer* t) { t->hash_table_next = nullptr; } -/* If a timer is added to a timer shard (either heap or a list), it cannot +/* If a timer is added to a timer shard (either heap or a list), it must * be pending. A timer is added to hash table only-if it is added to the * timer shard. * Therefore, if timer->pending is false, it cannot be in hash table */ @@ -489,7 +489,7 @@ static void timer_cancel(grpc_timer* timer) { 'queue_deadline_cap') into into shard->heap. Returns 'true' if shard->heap has atleast ONE element REQUIRES: shard->mu locked */ -static int refill_heap(timer_shard* shard, grpc_millis now) { +static bool refill_heap(timer_shard* shard, grpc_millis now) { /* Compute the new queue window width and bound by the limits: */ double computed_deadline_delta = grpc_time_averaged_stats_update_average(&shard->stats) * diff --git a/src/core/lib/iomgr/timer_heap.cc b/src/core/lib/iomgr/timer_heap.cc index 0c17d607eb..2c6a599149 100644 --- a/src/core/lib/iomgr/timer_heap.cc +++ b/src/core/lib/iomgr/timer_heap.cc @@ -95,7 +95,7 @@ void grpc_timer_heap_init(grpc_timer_heap* heap) { void grpc_timer_heap_destroy(grpc_timer_heap* heap) { gpr_free(heap->timers); } -int grpc_timer_heap_add(grpc_timer_heap* heap, grpc_timer* timer) { +bool grpc_timer_heap_add(grpc_timer_heap* heap, grpc_timer* timer) { if (heap->timer_count == heap->timer_capacity) { heap->timer_capacity = GPR_MAX(heap->timer_capacity + 1, heap->timer_capacity * 3 / 2); @@ -122,7 +122,7 @@ void grpc_timer_heap_remove(grpc_timer_heap* heap, grpc_timer* timer) { note_changed_priority(heap, heap->timers[i]); } -int grpc_timer_heap_is_empty(grpc_timer_heap* heap) { +bool grpc_timer_heap_is_empty(grpc_timer_heap* heap) { return heap->timer_count == 0; } diff --git a/src/core/lib/iomgr/timer_heap.h b/src/core/lib/iomgr/timer_heap.h index 503365d4cd..7b983e7133 100644 --- a/src/core/lib/iomgr/timer_heap.h +++ b/src/core/lib/iomgr/timer_heap.h @@ -29,8 +29,8 @@ typedef struct { uint32_t timer_capacity; } grpc_timer_heap; -/* return 1 if the new timer is the first timer in the heap */ -int grpc_timer_heap_add(grpc_timer_heap* heap, grpc_timer* timer); +/* return true if the new timer is the first timer in the heap */ +bool grpc_timer_heap_add(grpc_timer_heap* heap, grpc_timer* timer); void grpc_timer_heap_init(grpc_timer_heap* heap); void grpc_timer_heap_destroy(grpc_timer_heap* heap); @@ -39,6 +39,6 @@ void grpc_timer_heap_remove(grpc_timer_heap* heap, grpc_timer* timer); grpc_timer* grpc_timer_heap_top(grpc_timer_heap* heap); void grpc_timer_heap_pop(grpc_timer_heap* heap); -int grpc_timer_heap_is_empty(grpc_timer_heap* heap); +bool grpc_timer_heap_is_empty(grpc_timer_heap* heap); #endif /* GRPC_CORE_LIB_IOMGR_TIMER_HEAP_H */ diff --git a/src/core/lib/iomgr/timer_manager.cc b/src/core/lib/iomgr/timer_manager.cc index e272d228f8..54f19a9259 100644 --- a/src/core/lib/iomgr/timer_manager.cc +++ b/src/core/lib/iomgr/timer_manager.cc @@ -100,8 +100,7 @@ static void start_timer_thread_and_unlock(void) { void grpc_timer_manager_tick() { grpc_core::ExecCtx exec_ctx; - grpc_millis next = GRPC_MILLIS_INF_FUTURE; - grpc_timer_check(&next); + grpc_timer_check(nullptr); } static void run_some_timers() { @@ -110,9 +109,12 @@ static void run_some_timers() { // remove a waiter from the pool, and start another thread if necessary --g_waiter_count; if (g_waiter_count == 0 && g_threaded) { + // The number of timer threads is always increasing until all the threads + // are stopped. In rare cases, if a large number of timers fire + // simultaneously, we may end up using a large number of threads. start_timer_thread_and_unlock(); } else { - // if there's no thread waiting with a timeout, kick an existing + // if there's no thread waiting with a timeout, kick an existing untimed // waiter so that the next deadline is not missed if (!g_has_timed_waiter) { if (grpc_timer_check_trace.enabled()) { diff --git a/src/core/lib/iomgr/timer_manager.h b/src/core/lib/iomgr/timer_manager.h index 3c4cdda2c8..00dcdc461b 100644 --- a/src/core/lib/iomgr/timer_manager.h +++ b/src/core/lib/iomgr/timer_manager.h @@ -23,8 +23,8 @@ #include <stdbool.h> -/* Timer Manager tries to keep one thread waiting for the next timeout at all - times */ +/* Timer Manager tries to keep only one thread waiting for the next timeout at + all times, and thus effectively preventing the thundering herd problem. */ void grpc_timer_manager_init(void); void grpc_timer_manager_shutdown(void); |