6866591: G1: print update buffer processing stats more often

Summary: It adds parameter -XX:+G1SummarizeRSetStatsPeriod that causes update buffer processing information to be printed periodically. It also includes two small formatting changes.
Reviewed-by: jmasa, jcoomes, ysr

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2845,6 +2845,11 @@ G1CollectedHeap::do_collection_pause_at_safepoint() {
   if (PrintHeapAtGC) {
     Universe::print_heap_after_gc();
   }
+  if (G1SummarizeRSetStats &&
+      (G1SummarizeRSetStatsPeriod > 0) &&
+      (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
+    g1_rem_set()->print_summary_info();
+  }
 }
 
 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {

hotspot/src/share/vm/gc_implementation/g1/g1_globals.hpp

@@ -34,7 +34,7 @@
   product(intx, G1ConfidencePercent, 50,                                    \
           "Confidence level for MMU/pause predictions")                     \
                                                                             \
-  develop(intx, G1MarkingOverheadPercent, 0,                                   \
+  develop(intx, G1MarkingOverheadPercent, 0,                                \
           "Overhead of concurrent marking")                                 \
                                                                             \
   develop(bool, G1AccountConcurrentOverhead, false,                         \
@@ -47,7 +47,7 @@
   develop(bool, G1Gen, true,                                                \
           "If true, it will enable the generational G1")                    \
                                                                             \
-  develop(intx, G1GCPercent, 10,                                                \
+  develop(intx, G1GCPercent, 10,                                            \
           "The desired percent time spent on GC")                           \
                                                                             \
   develop(intx, G1PolicyVerbose, 0,                                         \
@@ -74,6 +74,12 @@
   diagnostic(bool, G1SummarizeRSetStats, false,                             \
           "Summarize remembered set processing info")                       \
                                                                             \
+  diagnostic(intx, G1SummarizeRSetStatsPeriod, 0,                           \
+          "The period (in number of GCs) at which we will generate "        \
+          "update buffer processing info "                                  \
+          "(0 means do not periodically generate this info); "              \
+          "it also requires -XX:+G1SummarizeRSetStats")                     \
+                                                                            \
   diagnostic(bool, G1SummarizeZFStats, false,                               \
           "Summarize zero-filling info")                                    \
                                                                             \