[wasm] Skip low-resolution time samples

In multiple counters we have peaks in the 0 microseconds and 1000
microseconds bucket, most probably coming from clients with a
low-resolution clock. Exclude those to get more precise timings.

R=jkummerow@chromium.org

Change-Id: I9b8377354920db4d0070198f440b57a7e86dc7bd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3902221Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83276}

src/wasm/function-compiler.cc

@@ -66,7 +66,7 @@ WasmCompilationResult WasmCompilationUnit::ExecuteFunctionCompilation(
 
   base::Optional<TimedHistogramScope> wasm_compile_function_time_scope;
   base::Optional<TimedHistogramScope> wasm_compile_huge_function_time_scope;
-  if (counters) {
+  if (counters && base::TimeTicks::IsHighResolution()) {
     if (func_body.end - func_body.start >= 100 * KB) {
       auto huge_size_histogram = SELECT_WASM_COUNTER(
           counters, env->module->origin, wasm, huge_function_size_bytes);

src/wasm/module-compiler.cc

@@ -1997,8 +1997,11 @@ std::shared_ptr<NativeModule> CompileToNativeModule(
     return native_module;
   }
 
-  TimedHistogramScope wasm_compile_module_time_scope(SELECT_WASM_COUNTER(
-      isolate->counters(), wasm_module->origin, wasm_compile, module_time));
+  base::Optional<TimedHistogramScope> wasm_compile_module_time_scope;
+  if (base::TimeTicks::IsHighResolution()) {
+    wasm_compile_module_time_scope.emplace(SELECT_WASM_COUNTER(
+        isolate->counters(), wasm_module->origin, wasm_compile, module_time));
+  }
 
   // Embedder usage count for declared shared memories.
   if (wasm_module->has_shared_memory) {
@@ -3052,9 +3055,11 @@ bool AsyncStreamingProcessor::Deserialize(
     base::Vector<const uint8_t> module_bytes,
     base::Vector<const uint8_t> wire_bytes) {
   TRACE_EVENT0("v8.wasm", "wasm.Deserialize");
-  TimedHistogramScope time_scope(
-      job_->isolate()->counters()->wasm_deserialization_time(),
-      job_->isolate());
+  base::Optional<TimedHistogramScope> time_scope;
+  if (base::TimeTicks::IsHighResolution()) {
+    time_scope.emplace(job_->isolate()->counters()->wasm_deserialization_time(),
+                       job_->isolate());
+  }
   // DeserializeNativeModule and FinishCompile assume that they are executed in
   // a HandleScope, and that a context is set on the isolate.
   HandleScope scope(job_->isolate_);
@@ -3297,8 +3302,11 @@ void CompilationStateImpl::InitializeCompilationProgressAfterDeserialization(
   TRACE_EVENT2("v8.wasm", "wasm.CompilationAfterDeserialization",
                "num_lazy_functions", lazy_functions.size(),
                "num_eager_functions", eager_functions.size());
-  TimedHistogramScope lazy_compile_time_scope(
-      counters()->wasm_compile_after_deserialize());
+  base::Optional<TimedHistogramScope> lazy_compile_time_scope;
+  if (base::TimeTicks::IsHighResolution()) {
+    lazy_compile_time_scope.emplace(
+        counters()->wasm_compile_after_deserialize());
+  }
 
   auto* module = native_module_->module();
   base::Optional<CodeSpaceWriteScope> lazy_code_space_write_scope;

src/wasm/module-instantiate.cc

@@ -521,12 +521,12 @@ MaybeHandle<WasmInstanceObject> InstanceBuilder::Build() {
 
   // From here on, we expect the build pipeline to run without exiting to JS.
   DisallowJavascriptExecution no_js(isolate_);
-  // Record build time into correct bucket, then build instance.
-  TimedHistogramScope wasm_instantiate_module_time_scope(SELECT_WASM_COUNTER(
-      isolate_->counters(), module_->origin, wasm_instantiate, module_time));
-  v8::metrics::WasmModuleInstantiated wasm_module_instantiated;
+  // Start a timer for instantiation time, if we have a high resolution timer.
   base::ElapsedTimer timer;
-  timer.Start();
+  if (base::TimeTicks::IsHighResolution()) {
+    timer.Start();
+  }
+  v8::metrics::WasmModuleInstantiated wasm_module_instantiated;
   NativeModule* native_module = module_object_->native_module();
 
   //--------------------------------------------------------------------------
@@ -855,11 +855,16 @@ MaybeHandle<WasmInstanceObject> InstanceBuilder::Build() {
   TRACE("Successfully built instance for module %p\n",
         module_object_->native_module());
   wasm_module_instantiated.success = true;
-  wasm_module_instantiated.wall_clock_duration_in_us =
-      timer.Elapsed().InMicroseconds();
-  timer.Stop();
-  isolate_->metrics_recorder()->DelayMainThreadEvent(wasm_module_instantiated,
-                                                     context_id_);
+  if (timer.IsStarted()) {
+    base::TimeDelta instantiation_time = timer.Elapsed();
+    wasm_module_instantiated.wall_clock_duration_in_us =
+        instantiation_time.InMicroseconds();
+    SELECT_WASM_COUNTER(isolate_->counters(), module_->origin, wasm_instantiate,
+                        module_time)
+        ->AddTimedSample(instantiation_time);
+    isolate_->metrics_recorder()->DelayMainThreadEvent(wasm_module_instantiated,
+                                                       context_id_);
+  }
   return instance;
 }