Retain maps embedded in optimized code for several garbage collections.

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 559 matching lines @@
            "semi-spaces")
 DEFINE_INT(semi_space_growth_factor, 2, "factor by which to grow the new space")
 DEFINE_BOOL(experimental_new_space_growth_heuristic, false,
             "Grow the new space based on the percentage of survivors instead "
             "of their absolute value.")
 DEFINE_INT(max_old_space_size, 0, "max size of the old space (in Mbytes)")
 DEFINE_INT(initial_old_space_size, 0, "initial old space size (in Mbytes)")
 DEFINE_INT(max_executable_size, 0, "max size of executable memory (in Mbytes)")
 DEFINE_BOOL(gc_global, false, "always perform global GCs")
 DEFINE_INT(gc_interval, -1, "garbage collect after <n> allocations")
+DEFINE_INT(retain_maps_for_n_gc, 2,
+           "keeps maps alive for <n> old space garbage collections")
 DEFINE_BOOL(trace_gc, false,
             "print one trace line following each garbage collection")
 DEFINE_BOOL(trace_gc_nvp, false,
             "print one detailed trace line in name=value format "
             "after each garbage collection")
 DEFINE_BOOL(trace_gc_ignore_scavenger, false,
             "do not print trace line after scavenger collection")
 DEFINE_BOOL(trace_idle_notification, false,
             "print one trace line following each idle notification")
 DEFINE_BOOL(trace_idle_notification_verbose, false,
@@ skipping 440 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