WIP: idle scavenge

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
diff --git a/runtime/vm/scavenger.cc b/runtime/vm/scavenger.cc
index 959a7f35e7f0cd8c96d866e193a3543a22329fbc..abd9f24def279d43e82ce2b4e59eed29ed6b5d94 100644
--- a/runtime/vm/scavenger.cc
+++ b/runtime/vm/scavenger.cc
@@ -420,6 +420,7 @@ void Scavenger::Epilogue(Isolate* isolate,
     // Remember the limit to which objects have been copied.
     survivor_end_ = top_;
   } else {
+    OS::Print("early tenuring!\n");
     // Move survivor end to the end of the to_ space, making all surviving
     // objects candidates for promotion next time.
     survivor_end_ = end_;
@@ -842,6 +843,9 @@ void Scavenger::Scavenge(bool invoke_api_callbacks) {
   // The API prologue/epilogue may create/destroy zones, so we must not
   // depend on zone allocations surviving beyond the epilogue callback.
   {
+    intptr_t scavenge_rate = ScavengeRateInBytesPerMicro();
+    intptr_t est_time = usage_before.used_in_words * kWordSize / scavenge_rate;
+
     StackZone zone(thread);
     // Setup the visitor and run the scavenge.
     ScavengerVisitor visitor(isolate, this, from);
@@ -862,9 +866,33 @@ void Scavenger::Scavenge(bool invoke_api_callbacks) {
     int64_t end = OS::GetCurrentMonotonicMicros();
     heap_->RecordTime(kProcessToSpace, middle - start);
     heap_->RecordTime(kIterateWeaks, end - middle);
+    SpaceUsage usage_after = GetCurrentUsage();
     stats_history_.Add(ScavengeStats(
-        start, end, usage_before, GetCurrentUsage(), promo_candidate_words,
+        start, end, usage_before, usage_after, promo_candidate_words,
         visitor.bytes_promoted() >> kWordSizeLog2));
+
+    intptr_t size_before = usage_before.used_in_words * kWordSize;
+    intptr_t survivor_tenured = visitor.bytes_promoted();
+    intptr_t survivor_nontenured = usage_after.used_in_words * kWordSize;
+    intptr_t actual_time = end - start;
+
+    OS::Print("rate=%7" Pd "B/us, "
+              "size=%5" Pd "kB, "
+              "survivor=%lf, "
+              "tenured=%lf, "
+              "nontenured=%lf, "
+              "estimated=%5" Pd "ms, "
+              "actual=%5" Pd "ms, "
+              "headroom=%5" Pd "us\n",
+              scavenge_rate,
+              size_before / KB,
+              (double)(survivor_tenured+survivor_nontenured)/(double)size_before,
+              (double)(survivor_tenured)/(double)size_before,
+              (double)(survivor_nontenured)/(double)size_before,
+              est_time / 1000,
+              actual_time / 1000,
+              (est_time - actual_time)
+              );
   }
   Epilogue(isolate, from, invoke_api_callbacks);