[heap] Measure time-to-safepoint

Now that --concurrent-inlining is already using LocalHeaps and requires
a global safepoint, let's measure how long it takes to stop-the-world.

Bug: v8:10315
Change-Id: I90f451448199fd43b9991849f4343f77e4aa3813
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2300544Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68886}

src/heap/gc-tracer.cc

@@ -566,6 +566,7 @@ void GCTracer::PrintNVP() const {
           "mutator=%.1f "
           "gc=%s "
           "reduce_memory=%d "
+          "stop_the_world=%.2f "
           "heap.prologue=%.2f "
           "heap.epilogue=%.2f "
           "heap.epilogue.reduce_new_space=%.2f "
@@ -609,7 +610,8 @@ void GCTracer::PrintNVP() const {
           "unmapper_chunks=%d "
           "context_disposal_rate=%.1f\n",
           duration, spent_in_mutator, current_.TypeName(true),
-          current_.reduce_memory, current_.scopes[Scope::HEAP_PROLOGUE],
+          current_.reduce_memory, current_.scopes[Scope::STOP_THE_WORLD],
+          current_.scopes[Scope::HEAP_PROLOGUE],
           current_.scopes[Scope::HEAP_EPILOGUE],
           current_.scopes[Scope::HEAP_EPILOGUE_REDUCE_NEW_SPACE],
           current_.scopes[Scope::HEAP_EXTERNAL_PROLOGUE],
@@ -657,6 +659,7 @@ void GCTracer::PrintNVP() const {
           "reduce_memory=%d "
           "minor_mc=%.2f "
           "finish_sweeping=%.2f "
+          "stop_the_world=%.2f "
           "mark=%.2f "
           "mark.seed=%.2f "
           "mark.roots=%.2f "
@@ -681,6 +684,7 @@ void GCTracer::PrintNVP() const {
           duration, spent_in_mutator, "mmc", current_.reduce_memory,
           current_.scopes[Scope::MINOR_MC],
           current_.scopes[Scope::MINOR_MC_SWEEPING],
+          current_.scopes[Scope::STOP_THE_WORLD],
           current_.scopes[Scope::MINOR_MC_MARK],
           current_.scopes[Scope::MINOR_MC_MARK_SEED],
           current_.scopes[Scope::MINOR_MC_MARK_ROOTS],
@@ -711,6 +715,7 @@ void GCTracer::PrintNVP() const {
           "mutator=%.1f "
           "gc=%s "
           "reduce_memory=%d "
+          "stop_the_world=%.2f "
           "heap.prologue=%.2f "
           "heap.embedder_tracing_epilogue=%.2f "
           "heap.epilogue=%.2f "
@@ -805,7 +810,8 @@ void GCTracer::PrintNVP() const {
           "context_disposal_rate=%.1f "
           "compaction_speed=%.f\n",
           duration, spent_in_mutator, current_.TypeName(true),
-          current_.reduce_memory, current_.scopes[Scope::HEAP_PROLOGUE],
+          current_.reduce_memory, current_.scopes[Scope::STOP_THE_WORLD],
+          current_.scopes[Scope::HEAP_PROLOGUE],
           current_.scopes[Scope::HEAP_EMBEDDER_TRACING_EPILOGUE],
           current_.scopes[Scope::HEAP_EPILOGUE],
           current_.scopes[Scope::HEAP_EPILOGUE_REDUCE_NEW_SPACE],

src/heap/safepoint.cc

@@ -6,6 +6,7 @@
 
 #include "src/handles/local-handles.h"
 #include "src/handles/persistent-handles.h"
+#include "src/heap/gc-tracer.h"
 #include "src/heap/heap.h"
 #include "src/heap/local-heap.h"
 
@@ -24,6 +25,8 @@ void GlobalSafepoint::EnterSafepointScope() {
 
   if (++active_safepoint_scopes_ > 1) return;
 
+  TRACE_GC(heap_->tracer(), GCTracer::Scope::STOP_THE_WORLD);
+
   local_heaps_mutex_.Lock();
   local_heap_of_this_thread_ = LocalHeap::Current();
 

src/init/heap-symbols.h

@@ -499,7 +499,8 @@
   F(SCAVENGER_SCAVENGE_UPDATE_REFS)                  \
   F(SCAVENGER_SCAVENGE_WEAK)                         \
   F(SCAVENGER_SCAVENGE_FINALIZE)                     \
-  F(SCAVENGER_SWEEP_ARRAY_BUFFERS)
+  F(SCAVENGER_SWEEP_ARRAY_BUFFERS)                   \
+  F(STOP_THE_WORLD)
 
 #define TRACER_BACKGROUND_SCOPES(F)               \
   F(BACKGROUND_ARRAY_BUFFER_FREE)                 \