executor_runner: print total execution time (#9342)

Makes it more convenient to check perf with the runner.

Author: swolchok

examples/portable/executor_runner/executor_runner.cpp

@@ -30,6 +30,7 @@
 #include <executorch/runtime/executor/method.h>
 #include <executorch/runtime/executor/program.h>
 #include <executorch/runtime/platform/log.h>
+#include <executorch/runtime/platform/platform.h>
 #include <executorch/runtime/platform/runtime.h>
 #ifdef ET_EVENT_TRACER_ENABLED
 #include <executorch/devtools/etdump/etdump_flatcc.h>
@@ -249,6 +250,7 @@ int main(int argc, char** argv) {
       (uint32_t)method.error());
   ET_LOG(Info, "Method loaded.");
 
+  et_timestamp_t time_spent_executing = 0;
   // Run the model.
   for (uint32_t i = 0; i < FLAGS_num_executions; i++) {
     ET_LOG(Debug, "Preparing inputs.");
@@ -267,17 +269,24 @@ int main(int argc, char** argv) {
         (uint32_t)inputs.error());
     ET_LOG(Debug, "Inputs prepared.");
 
+    const et_timestamp_t before_execute = et_pal_current_ticks();
     Error status = method->execute();
+    const et_timestamp_t after_execute = et_pal_current_ticks();
+    time_spent_executing += after_execute - before_execute;
     ET_CHECK_MSG(
         status == Error::Ok,
         "Execution of method %s failed with status 0x%" PRIx32,
         method_name,
         (uint32_t)status);
   }
+  const auto tick_ratio = et_pal_ticks_to_ns_multiplier();
+  constexpr auto NANOSECONDS_PER_MILLISECOND = 1000000;
   ET_LOG(
       Info,
-      "Model executed successfully %" PRIu32 " time(s).",
-      FLAGS_num_executions);
+      "Model executed successfully %" PRIu32 " time(s) in %f ms.",
+      FLAGS_num_executions,
+      static_cast<double>(time_spent_executing) * tick_ratio.numerator /
+          tick_ratio.denominator / NANOSECONDS_PER_MILLISECOND);
 
   // Print the outputs.
   std::vector<EValue> outputs(method->outputs_size());