8020155: PSR:PERF G1 not collecting old regions when humongous allocations interfer

Summary: Take _last_young_gc into account when deciding on starting a concurrent mark. Also reviewed-by: per.liden@oracle.com.
Reviewed-by: tschatzl, johnc

src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp

@@ -873,7 +873,7 @@ bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc
   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 
   if ((cur_used_bytes + alloc_byte_size) > marking_initiating_used_threshold) {
-    if (gcs_are_young()) {
+    if (gcs_are_young() && !_last_young_gc) {
       ergo_verbose5(ErgoConcCycles,
         "request concurrent cycle initiation",
         ergo_format_reason("occupancy higher than threshold")
@@ -931,7 +931,7 @@ void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, Evacua
   last_pause_included_initial_mark = during_initial_mark_pause();
   if (last_pause_included_initial_mark) {
     record_concurrent_mark_init_end(0.0);
-  } else if (!_last_young_gc && need_to_start_conc_mark("end of GC")) {
+  } else if (need_to_start_conc_mark("end of GC")) {
     // Note: this might have already been set, if during the last
     // pause we decided to start a cycle but at the beginning of
     // this pause we decided to postpone it. That's OK.