Create a few CUDA events per thread pool thread

Signed-off-by: Joaquin Anton Guirao <janton@nvidia.com>

dali/pipeline/util/thread_pool.cc

@@ -22,6 +22,8 @@
 #include "dali/core/cuda_error.h"
 #include "dali/core/device_guard.h"
 #include "dali/core/nvtx.h"
+#include "dali/core/cuda_event_pool.h"
+#include "dali/core/cuda_event.h"
 
 namespace dali {
 
@@ -41,6 +43,24 @@ ThreadPool::ThreadPool(int num_thread, int device_id, bool set_affinity, const c
                                         make_string("[DALI][TP", i, "]", name)));
   }
   tl_errors_.resize(num_thread);
+
+  if (device_id != CPU_ONLY_DEVICE_ID) {
+    static int num_events_per_thread = -1;
+    if (num_events_per_thread < 0) {
+      const char *num_events_per_thread_env = std::getenv("DALI_NUM_EVENTS_PER_THREAD");
+      num_events_per_thread = !num_events_per_thread_env || atoi(num_events_per_thread_env);
+    }
+    if (num_events_per_thread < 0)
+      num_events_per_thread = 4;
+
+    DeviceGuard dg(device_id);
+    auto &event_pool = CUDAEventPool::instance();
+
+    int num_events = num_thread * num_events_per_thread;
+    for (int i = 0; i < num_events; ++i) {
+      event_pool.Put(CUDAEvent::CreateWithFlags(cudaEventDisableTiming));
+    }
+  }
 }
 
 ThreadPool::~ThreadPool() {