🏄 [heap] Add page evacuation mode for new->old

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 235 matching lines @@
   DEFINE_BOOL(id, true, "enable " #description) \
   DEFINE_NEG_NEG_IMPLICATION(harmony_shipping, id)
 HARMONY_SHIPPING(FLAG_SHIPPING_FEATURES)
 #undef FLAG_SHIPPING_FEATURES
 
 // Flags for experimental implementation features.
 DEFINE_BOOL(compiled_keyed_generic_loads, false,
             "use optimizing compiler to generate keyed generic load stubs")
 DEFINE_BOOL(allocation_site_pretenuring, true,
             "pretenure with allocation sites")
+DEFINE_BOOL(page_promotion, true, "promote pages based on utilization")
+DEFINE_INT(page_promotion_threshold, 70,
+           "min percentage of live bytes on a page to enable fast evacuation")
 DEFINE_BOOL(trace_pretenuring, false,
             "trace pretenuring decisions of HAllocate instructions")
 DEFINE_BOOL(trace_pretenuring_statistics, false,
             "trace allocation site pretenuring statistics")
 DEFINE_BOOL(track_fields, true, "track fields with only smi values")
 DEFINE_BOOL(track_double_fields, true, "track fields with double values")
 DEFINE_BOOL(track_heap_object_fields, true, "track fields with heap values")
 DEFINE_BOOL(track_computed_fields, true, "track computed boilerplate fields")
 DEFINE_BOOL(harmony_instanceof_opt, true, "optimize ES6 instanceof support")
 DEFINE_IMPLICATION(track_double_fields, track_fields)
@@ skipping 897 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA