Merge pull request #11888 from ctiller/shardier

Autosize timer list shards

src/core/lib/iomgr/timer_generic.cc

@@ -25,6 +25,7 @@
 #include "src/core/lib/iomgr/timer.h"
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/cpu.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/sync.h>
@@ -37,8 +38,6 @@
 
 #define INVALID_HEAP_INDEX 0xffffffffu
 
-#define LOG2_NUM_SHARDS 5
-#define NUM_SHARDS (1 << LOG2_NUM_SHARDS)
 #define ADD_DEADLINE_SCALE 0.33
 #define MIN_QUEUE_WINDOW_DURATION 0.01
 #define MAX_QUEUE_WINDOW_DURATION 1
@@ -74,14 +73,16 @@ typedef struct {
   grpc_timer list;
 } timer_shard;
 
+static size_t g_num_shards;
+
 /* Array of timer shards. Whenever a timer (grpc_timer *) is added, its address
  * is hashed to select the timer shard to add the timer to */
-static timer_shard g_shards[NUM_SHARDS];
+static timer_shard* g_shards;
 
 /* Maintains a sorted list of timer shards (sorted by their min_deadline, i.e
  * the deadline of the next timer in each shard).
  * Access to this is protected by g_shared_mutables.mu */
-static timer_shard* g_shard_queue[NUM_SHARDS];
+static timer_shard** g_shard_queue;
 
 #ifndef NDEBUG
 
@@ -241,6 +242,11 @@ static gpr_atm compute_min_deadline(timer_shard* shard) {
 void grpc_timer_list_init(grpc_exec_ctx* exec_ctx) {
   uint32_t i;
 
+  g_num_shards = GPR_MIN(1, 2 * gpr_cpu_num_cores());
+  g_shards = (timer_shard*)gpr_zalloc(g_num_shards * sizeof(*g_shards));
+  g_shard_queue =
+      (timer_shard**)gpr_zalloc(g_num_shards * sizeof(*g_shard_queue));
+
   g_shared_mutables.initialized = true;
   g_shared_mutables.checker_mu = GPR_SPINLOCK_INITIALIZER;
   gpr_mu_init(&g_shared_mutables.mu);
@@ -250,7 +256,7 @@ void grpc_timer_list_init(grpc_exec_ctx* exec_ctx) {
   grpc_register_tracer(&grpc_timer_trace);
   grpc_register_tracer(&grpc_timer_check_trace);
 
-  for (i = 0; i < NUM_SHARDS; i++) {
+  for (i = 0; i < g_num_shards; i++) {
     timer_shard* shard = &g_shards[i];
     gpr_mu_init(&shard->mu);
     grpc_time_averaged_stats_init(&shard->stats, 1.0 / ADD_DEADLINE_SCALE, 0.1,
@@ -267,17 +273,19 @@ void grpc_timer_list_init(grpc_exec_ctx* exec_ctx) {
 }
 
 void grpc_timer_list_shutdown(grpc_exec_ctx* exec_ctx) {
-  int i;
+  size_t i;
   run_some_expired_timers(
       exec_ctx, GPR_ATM_MAX, NULL,
       GRPC_ERROR_CREATE_FROM_STATIC_STRING("Timer list shutdown"));
-  for (i = 0; i < NUM_SHARDS; i++) {
+  for (i = 0; i < g_num_shards; i++) {
     timer_shard* shard = &g_shards[i];
     gpr_mu_destroy(&shard->mu);
     grpc_timer_heap_destroy(&shard->heap);
   }
   gpr_mu_destroy(&g_shared_mutables.mu);
   gpr_tls_destroy(&g_last_seen_min_timer);
+  gpr_free(g_shards);
+  gpr_free(g_shard_queue);
   g_shared_mutables.initialized = false;
 }
 
@@ -311,7 +319,7 @@ static void note_deadline_change(timer_shard* shard) {
              g_shard_queue[shard->shard_queue_index - 1]->min_deadline) {
     swap_adjacent_shards_in_queue(shard->shard_queue_index - 1);
   }
-  while (shard->shard_queue_index < NUM_SHARDS - 1 &&
+  while (shard->shard_queue_index < g_num_shards - 1 &&
          shard->min_deadline >
              g_shard_queue[shard->shard_queue_index + 1]->min_deadline) {
     swap_adjacent_shards_in_queue(shard->shard_queue_index);
@@ -323,7 +331,7 @@ void grpc_timer_init_unset(grpc_timer* timer) { timer->pending = false; }
 void grpc_timer_init(grpc_exec_ctx* exec_ctx, grpc_timer* timer,
                      grpc_millis deadline, grpc_closure* closure) {
   int is_first_timer = 0;
-  timer_shard* shard = &g_shards[GPR_HASH_POINTER(timer, NUM_SHARDS)];
+  timer_shard* shard = &g_shards[GPR_HASH_POINTER(timer, g_num_shards)];
   timer->closure = closure;
   timer->deadline = deadline;
 
@@ -417,7 +425,7 @@ void grpc_timer_cancel(grpc_exec_ctx* exec_ctx, grpc_timer* timer) {
     return;
   }
 
-  timer_shard* shard = &g_shards[GPR_HASH_POINTER(timer, NUM_SHARDS)];
+  timer_shard* shard = &g_shards[GPR_HASH_POINTER(timer, g_num_shards)];
   gpr_mu_lock(&shard->mu);
   if (GRPC_TRACER_ON(grpc_timer_trace)) {
     gpr_log(GPR_DEBUG, "TIMER %p: CANCEL pending=%s", timer,