changeset 2748:20213c8a3c40

7050392: G1: Introduce flag to generate a log of the G1 ergonomic decisions Summary: It introduces ergonomic decision logging in G1 for the following heuristics: heap sizing, collection set construction, concurrent cycle initiation, and partially-young GC start/end. The code has a bit of refactoring in a few places to make the decision logging possible. It also replaces alternative ad-hoc logging that we have under different parameters and switches (G1_DEBUG, G1PolicyVerbose). Reviewed-by: johnc, ysr
author tonyp
date Wed, 07 Sep 2011 12:21:23 -0400
parents 27702f012017
children 05550041d664
files src/share/vm/gc_implementation/g1/collectionSetChooser.cpp src/share/vm/gc_implementation/g1/concurrentMark.cpp src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp src/share/vm/gc_implementation/g1/g1ErgoVerbose.cpp src/share/vm/gc_implementation/g1/g1ErgoVerbose.hpp src/share/vm/gc_implementation/g1/g1MMUTracker.cpp src/share/vm/gc_implementation/g1/vm_operations_g1.cpp
diffstat 9 files changed, 565 insertions(+), 209 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/collectionSetChooser.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/collectionSetChooser.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,7 @@
 #include "gc_implementation/g1/collectionSetChooser.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1ErgoVerbose.hpp"
 #include "memory/space.inline.hpp"
 
 CSetChooserCache::CSetChooserCache() {
@@ -358,6 +359,9 @@
   if (_cache.is_empty()) {
     assert(_curMarkedIndex == _numMarkedRegions,
            "if cache is empty, list should also be empty");
+    ergo_verbose0(ErgoCSetConstruction,
+                  "stop adding old regions to CSet",
+                  ergo_format_reason("cache is empty"));
     return NULL;
   }
 
@@ -368,10 +372,23 @@
   if (g1p->adaptive_young_list_length()) {
     if (time_remaining - predicted_time < 0.0) {
       g1h->check_if_region_is_too_expensive(predicted_time);
+      ergo_verbose2(ErgoCSetConstruction,
+                    "stop adding old regions to CSet",
+                    ergo_format_reason("predicted old region time higher than remaining time")
+                    ergo_format_ms("predicted old region time")
+                    ergo_format_ms("remaining time"),
+                    predicted_time, time_remaining);
       return NULL;
     }
   } else {
-    if (predicted_time > 2.0 * avg_prediction) {
+    double threshold = 2.0 * avg_prediction;
+    if (predicted_time > threshold) {
+      ergo_verbose2(ErgoCSetConstruction,
+                    "stop adding old regions to CSet",
+                    ergo_format_reason("predicted old region time higher than threshold")
+                    ergo_format_ms("predicted old region time")
+                    ergo_format_ms("threshold"),
+                    predicted_time, threshold);
       return NULL;
     }
   }
--- a/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -28,6 +28,7 @@
 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1ErgoVerbose.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
 #include "gc_implementation/g1/g1RemSet.hpp"
 #include "gc_implementation/g1/heapRegionRemSet.hpp"
@@ -1727,18 +1728,21 @@
 
   size_t known_garbage_bytes =
     g1_par_count_task.used_bytes() - g1_par_count_task.live_bytes();
-#if 0
-  gclog_or_tty->print_cr("used %1.2lf, live %1.2lf, garbage %1.2lf",
-                         (double) g1_par_count_task.used_bytes() / (double) (1024 * 1024),
-                         (double) g1_par_count_task.live_bytes() / (double) (1024 * 1024),
-                         (double) known_garbage_bytes / (double) (1024 * 1024));
-#endif // 0
   g1p->set_known_garbage_bytes(known_garbage_bytes);
 
   size_t start_used_bytes = g1h->used();
   _at_least_one_mark_complete = true;
   g1h->set_marking_complete();
 
+  ergo_verbose4(ErgoConcCycles,
+           "finish cleanup",
+           ergo_format_byte("occupancy")
+           ergo_format_byte("capacity")
+           ergo_format_byte_perc("known garbage"),
+           start_used_bytes, g1h->capacity(),
+           known_garbage_bytes,
+           ((double) known_garbage_bytes / (double) g1h->capacity()) * 100.0);
+
   double count_end = os::elapsedTime();
   double this_final_counting_time = (count_end - start);
   if (G1PrintParCleanupStats) {
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -31,6 +31,7 @@
 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1ErgoVerbose.hpp"
 #include "gc_implementation/g1/g1MarkSweep.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
 #include "gc_implementation/g1/g1RemSet.inline.hpp"
@@ -577,6 +578,11 @@
     res = new_region_try_secondary_free_list();
   }
   if (res == NULL && do_expand) {
+    ergo_verbose1(ErgoHeapSizing,
+                  "attempt heap expansion",
+                  ergo_format_reason("region allocation request failed")
+                  ergo_format_byte("allocation request"),
+                  word_size * HeapWordSize);
     if (expand(word_size * HeapWordSize)) {
       // Even though the heap was expanded, it might not have reached
       // the desired size. So, we cannot assume that the allocation
@@ -790,6 +796,11 @@
       // room available.
       assert(num_regions > fs, "earlier allocation should have succeeded");
 
+      ergo_verbose1(ErgoHeapSizing,
+                    "attempt heap expansion",
+                    ergo_format_reason("humongous allocation request failed")
+                    ergo_format_byte("allocation request"),
+                    word_size * HeapWordSize);
       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
         // Even though the heap was expanded, it might not have
         // reached the desired size. So, we cannot assume that the
@@ -906,6 +917,8 @@
 
       if (GC_locker::is_active_and_needs_gc()) {
         if (g1_policy()->can_expand_young_list()) {
+          // No need for an ergo verbose message here,
+          // can_expand_young_list() does this when it returns true.
           result = _mutator_alloc_region.attempt_allocation_force(word_size,
                                                       false /* bot_updates */);
           if (result != NULL) {
@@ -1477,63 +1490,34 @@
   // we'll try to make the capacity smaller than it, not greater).
   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
 
-  if (PrintGC && Verbose) {
-    const double free_percentage =
-      (double) free_after_gc / (double) capacity_after_gc;
-    gclog_or_tty->print_cr("Computing new size after full GC ");
-    gclog_or_tty->print_cr("  "
-                           "  minimum_free_percentage: %6.2f",
-                           minimum_free_percentage);
-    gclog_or_tty->print_cr("  "
-                           "  maximum_free_percentage: %6.2f",
-                           maximum_free_percentage);
-    gclog_or_tty->print_cr("  "
-                           "  capacity: %6.1fK"
-                           "  minimum_desired_capacity: %6.1fK"
-                           "  maximum_desired_capacity: %6.1fK",
-                           (double) capacity_after_gc / (double) K,
-                           (double) minimum_desired_capacity / (double) K,
-                           (double) maximum_desired_capacity / (double) K);
-    gclog_or_tty->print_cr("  "
-                           "  free_after_gc: %6.1fK"
-                           "  used_after_gc: %6.1fK",
-                           (double) free_after_gc / (double) K,
-                           (double) used_after_gc / (double) K);
-    gclog_or_tty->print_cr("  "
-                           "   free_percentage: %6.2f",
-                           free_percentage);
-  }
   if (capacity_after_gc < minimum_desired_capacity) {
     // Don't expand unless it's significant
     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
-    if (expand(expand_bytes)) {
-      if (PrintGC && Verbose) {
-        gclog_or_tty->print_cr("  "
-                               "  expanding:"
-                               "  max_heap_size: %6.1fK"
-                               "  minimum_desired_capacity: %6.1fK"
-                               "  expand_bytes: %6.1fK",
-                               (double) max_heap_size / (double) K,
-                               (double) minimum_desired_capacity / (double) K,
-                               (double) expand_bytes / (double) K);
-      }
-    }
+    ergo_verbose4(ErgoHeapSizing,
+                  "attempt heap expansion",
+                  ergo_format_reason("capacity lower than "
+                                     "min desired capacity after Full GC")
+                  ergo_format_byte("capacity")
+                  ergo_format_byte("occupancy")
+                  ergo_format_byte_perc("min desired capacity"),
+                  capacity_after_gc, used_after_gc,
+                  minimum_desired_capacity, (double) MinHeapFreeRatio);
+    expand(expand_bytes);
 
     // No expansion, now see if we want to shrink
   } else if (capacity_after_gc > maximum_desired_capacity) {
     // Capacity too large, compute shrinking size
     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
+    ergo_verbose4(ErgoHeapSizing,
+                  "attempt heap shrinking",
+                  ergo_format_reason("capacity higher than "
+                                     "max desired capacity after Full GC")
+                  ergo_format_byte("capacity")
+                  ergo_format_byte("occupancy")
+                  ergo_format_byte_perc("max desired capacity"),
+                  capacity_after_gc, used_after_gc,
+                  maximum_desired_capacity, (double) MaxHeapFreeRatio);
     shrink(shrink_bytes);
-    if (PrintGC && Verbose) {
-      gclog_or_tty->print_cr("  "
-                             "  shrinking:"
-                             "  min_heap_size: %6.1fK"
-                             "  maximum_desired_capacity: %6.1fK"
-                             "  shrink_bytes: %6.1fK",
-                             (double) min_heap_size / (double) K,
-                             (double) maximum_desired_capacity / (double) K,
-                             (double) shrink_bytes / (double) K);
-    }
   }
 }
 
@@ -1619,6 +1603,11 @@
   verify_region_sets_optional();
 
   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
+  ergo_verbose1(ErgoHeapSizing,
+                "attempt heap expansion",
+                ergo_format_reason("allocation request failed")
+                ergo_format_byte("allocation request"),
+                word_size * HeapWordSize);
   if (expand(expand_bytes)) {
     _hrs.verify_optional();
     verify_region_sets_optional();
@@ -1646,11 +1635,11 @@
   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
                                        HeapRegion::GrainBytes);
-
-  if (Verbose && PrintGC) {
-    gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
-                           old_mem_size/K, aligned_expand_bytes/K);
-  }
+  ergo_verbose2(ErgoHeapSizing,
+                "expand the heap",
+                ergo_format_byte("requested expansion amount")
+                ergo_format_byte("attempted expansion amount"),
+                expand_bytes, aligned_expand_bytes);
 
   // First commit the memory.
   HeapWord* old_end = (HeapWord*) _g1_storage.high();
@@ -1694,6 +1683,9 @@
       assert(curr == mr.end(), "post-condition");
     }
   } else {
+    ergo_verbose0(ErgoHeapSizing,
+                  "did not expand the heap",
+                  ergo_format_reason("heap expansion operation failed"));
     // The expansion of the virtual storage space was unsuccessful.
     // Let's see if it was because we ran out of swap.
     if (G1ExitOnExpansionFailure &&
@@ -1702,13 +1694,6 @@
       vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
     }
   }
-
-  if (Verbose && PrintGC) {
-    size_t new_mem_size = _g1_storage.committed_size();
-    gclog_or_tty->print_cr("...%s, expanded to %ldK",
-                           (successful ? "Successful" : "Failed"),
-                           new_mem_size/K);
-  }
   return successful;
 }
 
@@ -1722,6 +1707,13 @@
   MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
   HeapWord* old_end = (HeapWord*) _g1_storage.high();
   assert(mr.end() == old_end, "post-condition");
+
+  ergo_verbose3(ErgoHeapSizing,
+                "shrink the heap",
+                ergo_format_byte("requested shrinking amount")
+                ergo_format_byte("aligned shrinking amount")
+                ergo_format_byte("attempted shrinking amount"),
+                shrink_bytes, aligned_shrink_bytes, mr.byte_size());
   if (mr.byte_size() > 0) {
     if (_hr_printer.is_active()) {
       HeapWord* curr = mr.end();
@@ -1740,13 +1732,10 @@
     _expansion_regions += num_regions_deleted;
     update_committed_space(old_end, new_end);
     HeapRegionRemSet::shrink_heap(n_regions());
-
-    if (Verbose && PrintGC) {
-      size_t new_mem_size = _g1_storage.committed_size();
-      gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
-                             old_mem_size/K, aligned_shrink_bytes/K,
-                             new_mem_size/K);
-    }
+  } else {
+    ergo_verbose0(ErgoHeapSizing,
+                  "did not shrink the heap",
+                  ergo_format_reason("heap shrinking operation failed"));
   }
 }
 
@@ -3579,6 +3568,8 @@
         size_t expand_bytes = g1_policy()->expansion_amount();
         if (expand_bytes > 0) {
           size_t bytes_before = capacity();
+          // No need for an ergo verbose message here,
+          // expansion_amount() does this when it returns a value > 0.
           if (!expand(expand_bytes)) {
             // We failed to expand the heap so let's verify that
             // committed/uncommitted amount match the backing store
@@ -3732,13 +3723,6 @@
   bool do_object_b(oop p) {
     // It is reachable if it is outside the collection set, or is inside
     // and forwarded.
-
-#ifdef G1_DEBUG
-    gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
-                           (void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
-                           !_g1->obj_in_cs(p) || p->is_forwarded());
-#endif // G1_DEBUG
-
     return !_g1->obj_in_cs(p) || p->is_forwarded();
   }
 };
@@ -3750,20 +3734,9 @@
   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
   void do_oop(      oop* p) {
     oop obj = *p;
-#ifdef G1_DEBUG
-    if (PrintGC && Verbose) {
-      gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
-                             p, (void*) obj, (void*) *p);
-    }
-#endif // G1_DEBUG
-
     if (_g1->obj_in_cs(obj)) {
       assert( obj->is_forwarded(), "invariant" );
       *p = obj->forwardee();
-#ifdef G1_DEBUG
-      gclog_or_tty->print_cr("     in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
-                             (void*) obj, (void*) *p);
-#endif // G1_DEBUG
     }
   }
 };
--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -28,6 +28,7 @@
 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1ErgoVerbose.hpp"
 #include "gc_implementation/g1/heapRegionRemSet.hpp"
 #include "gc_implementation/shared/gcPolicyCounters.hpp"
 #include "runtime/arguments.hpp"
@@ -271,15 +272,26 @@
   _recorded_survivor_tail(NULL),
   _survivors_age_table(true),
 
-  _gc_overhead_perc(0.0)
-
-{
+  _gc_overhead_perc(0.0) {
+
   // Set up the region size and associated fields. Given that the
   // policy is created before the heap, we have to set this up here,
   // so it's done as soon as possible.
   HeapRegion::setup_heap_region_size(Arguments::min_heap_size());
   HeapRegionRemSet::setup_remset_size();
 
+  G1ErgoVerbose::initialize();
+  if (PrintAdaptiveSizePolicy) {
+    // Currently, we only use a single switch for all the heuristics.
+    G1ErgoVerbose::set_enabled(true);
+    // Given that we don't currently have a verboseness level
+    // parameter, we'll hardcode this to high. This can be easily
+    // changed in the future.
+    G1ErgoVerbose::set_level(ErgoHigh);
+  } else {
+    G1ErgoVerbose::set_enabled(false);
+  }
+
   // Verify PLAB sizes
   const uint region_size = HeapRegion::GrainWords;
   if (YoungPLABSize > region_size || OldPLABSize > region_size) {
@@ -959,11 +971,9 @@
 G1CollectorPolicy::
 record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
                                          size_t max_live_bytes) {
-  if (_n_marks < 2) _n_marks++;
-  if (G1PolicyVerbose > 0)
-    gclog_or_tty->print_cr("At end of marking, max_live is " SIZE_FORMAT " MB "
-                           " (of " SIZE_FORMAT " MB heap).",
-                           max_live_bytes/M, _g1->capacity()/M);
+  if (_n_marks < 2) {
+    _n_marks++;
+  }
 }
 
 // The important thing about this is that it includes "os::elapsedTime".
@@ -977,14 +987,6 @@
   _mmu_tracker->add_pause(_mark_cleanup_start_sec, end_time_sec, true);
 
   _num_markings++;
-
-  // We did a marking, so reset the "since_last_mark" variables.
-  double considerConcMarkCost = 1.0;
-  // If there are available processors, concurrent activity is free...
-  if (Threads::number_of_non_daemon_threads() * 2 <
-      os::active_processor_count()) {
-    considerConcMarkCost = 0.0;
-  }
   _n_pauses_at_mark_end = _n_pauses;
   _n_marks_since_last_pause++;
 }
@@ -1148,20 +1150,37 @@
   if (last_pause_included_initial_mark)
     record_concurrent_mark_init_end(0.0);
 
-  size_t min_used_targ =
+  size_t marking_initiating_used_threshold =
     (_g1->capacity() / 100) * InitiatingHeapOccupancyPercent;
 
-
   if (!_g1->mark_in_progress() && !_last_full_young_gc) {
     assert(!last_pause_included_initial_mark, "invariant");
-    if (cur_used_bytes > min_used_targ &&
-      cur_used_bytes > _prev_collection_pause_used_at_end_bytes) {
+    if (cur_used_bytes > marking_initiating_used_threshold) {
+      if (cur_used_bytes > _prev_collection_pause_used_at_end_bytes) {
         assert(!during_initial_mark_pause(), "we should not see this here");
 
+        ergo_verbose3(ErgoConcCycles,
+                      "request concurrent cycle initiation",
+                      ergo_format_reason("occupancy higher than threshold")
+                      ergo_format_byte("occupancy")
+                      ergo_format_byte_perc("threshold"),
+                      cur_used_bytes,
+                      marking_initiating_used_threshold,
+                      (double) InitiatingHeapOccupancyPercent);
+
         // 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.
         set_initiate_conc_mark_if_possible();
+      } else {
+        ergo_verbose2(ErgoConcCycles,
+                  "do not request concurrent cycle initiation",
+                  ergo_format_reason("occupancy lower than previous occupancy")
+                  ergo_format_byte("occupancy")
+                  ergo_format_byte("previous occupancy"),
+                  cur_used_bytes,
+                  _prev_collection_pause_used_at_end_bytes);
+      }
     }
   }
 
@@ -1437,16 +1456,45 @@
   }
 
   if (_last_full_young_gc) {
+    ergo_verbose2(ErgoPartiallyYoungGCs,
+                  "start partially-young GCs",
+                  ergo_format_byte_perc("known garbage"),
+                  _known_garbage_bytes, _known_garbage_ratio * 100.0);
     set_full_young_gcs(false);
     _last_full_young_gc = false;
   }
 
   if ( !_last_young_gc_full ) {
-    if ( _should_revert_to_full_young_gcs ||
-      _known_garbage_ratio < 0.05 ||
-      (adaptive_young_list_length() &&
-      (get_gc_eff_factor() * cur_efficiency < predict_young_gc_eff())) ) {
-        set_full_young_gcs(true);
+    if (_should_revert_to_full_young_gcs) {
+      ergo_verbose2(ErgoPartiallyYoungGCs,
+                    "end partially-young GCs",
+                    ergo_format_reason("partially-young GCs end requested")
+                    ergo_format_byte_perc("known garbage"),
+                    _known_garbage_bytes, _known_garbage_ratio * 100.0);
+      set_full_young_gcs(true);
+    } else if (_known_garbage_ratio < 0.05) {
+      ergo_verbose3(ErgoPartiallyYoungGCs,
+               "end partially-young GCs",
+               ergo_format_reason("known garbage percent lower than threshold")
+               ergo_format_byte_perc("known garbage")
+               ergo_format_perc("threshold"),
+               _known_garbage_bytes, _known_garbage_ratio * 100.0,
+               0.05 * 100.0);
+      set_full_young_gcs(true);
+    } else if (adaptive_young_list_length() &&
+              (get_gc_eff_factor() * cur_efficiency < predict_young_gc_eff())) {
+      ergo_verbose5(ErgoPartiallyYoungGCs,
+                    "end partially-young GCs",
+                    ergo_format_reason("current GC efficiency lower than "
+                                       "predicted fully-young GC efficiency")
+                    ergo_format_double("GC efficiency factor")
+                    ergo_format_double("current GC efficiency")
+                    ergo_format_double("predicted fully-young GC efficiency")
+                    ergo_format_byte_perc("known garbage"),
+                    get_gc_eff_factor(), cur_efficiency,
+                    predict_young_gc_eff(),
+                    _known_garbage_bytes, _known_garbage_ratio * 100.0);
+      set_full_young_gcs(true);
     }
   }
   _should_revert_to_full_young_gcs = false;
@@ -1877,6 +1925,12 @@
   // I don't think we need to do this when in young GC mode since
   // marking will be initiated next time we hit the soft limit anyway...
   if (predicted_time_ms > _expensive_region_limit_ms) {
+    ergo_verbose2(ErgoPartiallyYoungGCs,
+              "request partially-young GCs end",
+              ergo_format_reason("predicted region time higher than threshold")
+              ergo_format_ms("predicted region time")
+              ergo_format_ms("threshold"),
+              predicted_time_ms, _expensive_region_limit_ms);
     // no point in doing another partial one
     _should_revert_to_full_young_gcs = true;
   }
@@ -1986,7 +2040,9 @@
 }
 
 size_t G1CollectorPolicy::expansion_amount() {
-  if ((recent_avg_pause_time_ratio() * 100.0) > _gc_overhead_perc) {
+  double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
+  double threshold = _gc_overhead_perc;
+  if (recent_gc_overhead > threshold) {
     // We will double the existing space, or take
     // G1ExpandByPercentOfAvailable % of the available expansion
     // space, whichever is smaller, bounded below by a minimum
@@ -2001,20 +2057,19 @@
     expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
-    if (G1PolicyVerbose > 1) {
-      gclog_or_tty->print("Decided to expand: ratio = %5.2f, "
-                 "committed = %d%s, uncommited = %d%s, via pct = %d%s.\n"
-                 "                   Answer = %d.\n",
-                 recent_avg_pause_time_ratio(),
-                 byte_size_in_proper_unit(committed_bytes),
-                 proper_unit_for_byte_size(committed_bytes),
-                 byte_size_in_proper_unit(uncommitted_bytes),
-                 proper_unit_for_byte_size(uncommitted_bytes),
-                 byte_size_in_proper_unit(expand_bytes_via_pct),
-                 proper_unit_for_byte_size(expand_bytes_via_pct),
-                 byte_size_in_proper_unit(expand_bytes),
-                 proper_unit_for_byte_size(expand_bytes));
-    }
+
+    ergo_verbose5(ErgoHeapSizing,
+                  "attempt heap expansion",
+                  ergo_format_reason("recent GC overhead higher than "
+                                     "threshold after GC")
+                  ergo_format_perc("recent GC overhead")
+                  ergo_format_perc("threshold")
+                  ergo_format_byte("uncommitted")
+                  ergo_format_byte_perc("calculated expansion amount"),
+                  recent_gc_overhead, threshold,
+                  uncommitted_bytes,
+                  expand_bytes_via_pct, (double) G1ExpandByPercentOfAvailable);
+
     return expand_bytes;
   } else {
     return 0;
@@ -2237,8 +2292,7 @@
 #endif // PRODUCT
 }
 
-void
-G1CollectorPolicy::update_region_num(bool young) {
+void G1CollectorPolicy::update_region_num(bool young) {
   if (young) {
     ++_region_num_young;
   } else {
@@ -2315,13 +2369,23 @@
 }
 #endif
 
-bool
-G1CollectorPolicy::force_initial_mark_if_outside_cycle() {
+bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(
+                                                     GCCause::Cause gc_cause) {
   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
   if (!during_cycle) {
+    ergo_verbose1(ErgoConcCycles,
+                  "request concurrent cycle initiation",
+                  ergo_format_reason("requested by GC cause")
+                  ergo_format_str("GC cause"),
+                  GCCause::to_string(gc_cause));
     set_initiate_conc_mark_if_possible();
     return true;
   } else {
+    ergo_verbose1(ErgoConcCycles,
+                  "do not request concurrent cycle initiation",
+                  ergo_format_reason("concurrent cycle already in progress")
+                  ergo_format_str("GC cause"),
+                  GCCause::to_string(gc_cause));
     return false;
   }
 }
@@ -2353,6 +2417,10 @@
       // And we can now clear initiate_conc_mark_if_possible() as
       // we've already acted on it.
       clear_initiate_conc_mark_if_possible();
+
+      ergo_verbose0(ErgoConcCycles,
+                  "initiate concurrent cycle",
+                  ergo_format_reason("concurrent cycle initiation requested"));
     } else {
       // The concurrent marking thread is still finishing up the
       // previous cycle. If we start one right now the two cycles
@@ -2366,6 +2434,9 @@
       // and, if it's in a yield point, it's waiting for us to
       // finish. So, at this point we will not start a cycle and we'll
       // let the concurrent marking thread complete the last one.
+      ergo_verbose0(ErgoConcCycles,
+                    "do not initiate concurrent cycle",
+                    ergo_format_reason("concurrent cycle already in progress"));
     }
   }
 }
@@ -2756,6 +2827,8 @@
   // Set this here - in case we're not doing young collections.
   double non_young_start_time_sec = os::elapsedTime();
 
+  YoungList* young_list = _g1->young_list();
+
   start_recording_regions();
 
   guarantee(target_pause_time_ms > 0.0,
@@ -2768,61 +2841,62 @@
 
   double time_remaining_ms = target_pause_time_ms - base_time_ms;
 
+  ergo_verbose3(ErgoCSetConstruction | ErgoHigh,
+                "start choosing CSet",
+                ergo_format_ms("predicted base time")
+                ergo_format_ms("remaining time")
+                ergo_format_ms("target pause time"),
+                base_time_ms, time_remaining_ms, target_pause_time_ms);
+
   // the 10% and 50% values are arbitrary...
-  if (time_remaining_ms < 0.10 * target_pause_time_ms) {
+  double threshold = 0.10 * target_pause_time_ms;
+  if (time_remaining_ms < threshold) {
+    double prev_time_remaining_ms = time_remaining_ms;
     time_remaining_ms = 0.50 * target_pause_time_ms;
     _within_target = false;
+    ergo_verbose3(ErgoCSetConstruction,
+                  "adjust remaining time",
+                  ergo_format_reason("remaining time lower than threshold")
+                  ergo_format_ms("remaining time")
+                  ergo_format_ms("threshold")
+                  ergo_format_ms("adjusted remaining time"),
+                  prev_time_remaining_ms, threshold, time_remaining_ms);
   } else {
     _within_target = true;
   }
 
-  // We figure out the number of bytes available for future to-space.
-  // For new regions without marking information, we must assume the
-  // worst-case of complete survival.  If we have marking information for a
-  // region, we can bound the amount of live data.  We can add a number of
-  // such regions, as long as the sum of the live data bounds does not
-  // exceed the available evacuation space.
-  size_t max_live_bytes = _g1->free_regions() * HeapRegion::GrainBytes;
-
-  size_t expansion_bytes =
-    _g1->expansion_regions() * HeapRegion::GrainBytes;
+  size_t expansion_bytes = _g1->expansion_regions() * HeapRegion::GrainBytes;
+
+  HeapRegion* hr;
+  double young_start_time_sec = os::elapsedTime();
 
   _collection_set_bytes_used_before = 0;
   _collection_set_size = 0;
-
-  // Adjust for expansion and slop.
-  max_live_bytes = max_live_bytes + expansion_bytes;
-
-  HeapRegion* hr;
-  double young_start_time_sec = os::elapsedTime();
-
-  if (G1PolicyVerbose > 0) {
-    gclog_or_tty->print_cr("Adding %d young regions to the CSet",
-      _g1->young_list()->length());
-  }
-
   _young_cset_length  = 0;
   _last_young_gc_full = full_young_gcs() ? true : false;
 
-  if (_last_young_gc_full)
+  if (_last_young_gc_full) {
     ++_full_young_pause_num;
-  else
+  } else {
     ++_partial_young_pause_num;
+  }
 
   // The young list is laid with the survivor regions from the previous
   // pause are appended to the RHS of the young list, i.e.
   //   [Newly Young Regions ++ Survivors from last pause].
 
-  hr = _g1->young_list()->first_survivor_region();
+  size_t survivor_region_num = young_list->survivor_length();
+  size_t eden_region_num = young_list->length() - survivor_region_num;
+  size_t old_region_num = 0;
+  hr = young_list->first_survivor_region();
   while (hr != NULL) {
     assert(hr->is_survivor(), "badly formed young list");
     hr->set_young();
     hr = hr->get_next_young_region();
   }
 
-  // Clear the fields that point to the survivor list - they are
-  // all young now.
-  _g1->young_list()->clear_survivors();
+  // Clear the fields that point to the survivor list - they are all young now.
+  young_list->clear_survivors();
 
   if (_g1->mark_in_progress())
     _g1->concurrent_mark()->register_collection_set_finger(_inc_cset_max_finger);
@@ -2831,14 +2905,17 @@
   _collection_set = _inc_cset_head;
   _collection_set_size = _inc_cset_size;
   _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
-
-  // For young regions in the collection set, we assume the worst
-  // case of complete survival
-  max_live_bytes -= _inc_cset_size * HeapRegion::GrainBytes;
-
   time_remaining_ms -= _inc_cset_predicted_elapsed_time_ms;
   predicted_pause_time_ms += _inc_cset_predicted_elapsed_time_ms;
 
+  ergo_verbose3(ErgoCSetConstruction | ErgoHigh,
+                "add young regions to CSet",
+                ergo_format_region("eden")
+                ergo_format_region("survivors")
+                ergo_format_ms("predicted young region time"),
+                eden_region_num, survivor_region_num,
+                _inc_cset_predicted_elapsed_time_ms);
+
   // The number of recorded young regions is the incremental
   // collection set's current size
   set_recorded_young_regions(_inc_cset_size);
@@ -2848,14 +2925,7 @@
   set_predicted_bytes_to_copy(_inc_cset_predicted_bytes_to_copy);
 #endif // PREDICTIONS_VERBOSE
 
-  if (G1PolicyVerbose > 0) {
-    gclog_or_tty->print_cr("  Added " PTR_FORMAT " Young Regions to CS.",
-      _inc_cset_size);
-    gclog_or_tty->print_cr("    (" SIZE_FORMAT " KB left in heap.)",
-      max_live_bytes/K);
-  }
-
-  assert(_inc_cset_size == _g1->young_list()->length(), "Invariant");
+  assert(_inc_cset_size == young_list->length(), "Invariant");
 
   double young_end_time_sec = os::elapsedTime();
   _recorded_young_cset_choice_time_ms =
@@ -2869,6 +2939,8 @@
     NumberSeq seq;
     double avg_prediction = 100000000000000000.0; // something very large
 
+    size_t prev_collection_set_size = _collection_set_size;
+    double prev_predicted_pause_time_ms = predicted_pause_time_ms;
     do {
       hr = _collectionSetChooser->getNextMarkedRegion(time_remaining_ms,
                                                       avg_prediction);
@@ -2878,23 +2950,58 @@
         predicted_pause_time_ms += predicted_time_ms;
         add_to_collection_set(hr);
         record_non_young_cset_region(hr);
-        max_live_bytes -= MIN2(hr->max_live_bytes(), max_live_bytes);
-        if (G1PolicyVerbose > 0) {
-          gclog_or_tty->print_cr("    (" SIZE_FORMAT " KB left in heap.)",
-                        max_live_bytes/K);
-        }
         seq.add(predicted_time_ms);
         avg_prediction = seq.avg() + seq.sd();
       }
-      should_continue =
-        ( hr != NULL) &&
-        ( (adaptive_young_list_length()) ? time_remaining_ms > 0.0
-          : _collection_set_size < _young_list_fixed_length );
+
+      should_continue = true;
+      if (hr == NULL) {
+        // No need for an ergo verbose message here,
+        // getNextMarkRegion() does this when it returns NULL.
+        should_continue = false;
+      } else {
+        if (adaptive_young_list_length()) {
+          if (time_remaining_ms < 0.0) {
+            ergo_verbose1(ErgoCSetConstruction,
+                          "stop adding old regions to CSet",
+                          ergo_format_reason("remaining time is lower than 0")
+                          ergo_format_ms("remaining time"),
+                          time_remaining_ms);
+            should_continue = false;
+          }
+        } else {
+          if (_collection_set_size < _young_list_fixed_length) {
+            ergo_verbose2(ErgoCSetConstruction,
+                          "stop adding old regions to CSet",
+                          ergo_format_reason("CSet length lower than target")
+                          ergo_format_region("CSet")
+                          ergo_format_region("young target"),
+                          _collection_set_size, _young_list_fixed_length);
+            should_continue = false;
+          }
+        }
+      }
     } while (should_continue);
 
     if (!adaptive_young_list_length() &&
-        _collection_set_size < _young_list_fixed_length)
+        _collection_set_size < _young_list_fixed_length) {
+      ergo_verbose2(ErgoCSetConstruction,
+                    "request partially-young GCs end",
+                    ergo_format_reason("CSet length lower than target")
+                    ergo_format_region("CSet")
+                    ergo_format_region("young target"),
+                    _collection_set_size, _young_list_fixed_length);
       _should_revert_to_full_young_gcs  = true;
+    }
+
+    old_region_num = _collection_set_size - prev_collection_set_size;
+
+    ergo_verbose2(ErgoCSetConstruction | ErgoHigh,
+                  "add old regions to CSet",
+                  ergo_format_region("old")
+                  ergo_format_ms("predicted old region time"),
+                  old_region_num,
+                  predicted_pause_time_ms - prev_predicted_pause_time_ms);
   }
 
   stop_incremental_cset_building();
@@ -2903,6 +3010,16 @@
 
   end_recording_regions();
 
+  ergo_verbose5(ErgoCSetConstruction,
+                "finish choosing CSet",
+                ergo_format_region("eden")
+                ergo_format_region("survivors")
+                ergo_format_region("old")
+                ergo_format_ms("predicted pause time")
+                ergo_format_ms("target pause time"),
+                eden_region_num, survivor_region_num, old_region_num,
+                predicted_pause_time_ms, target_pause_time_ms);
+
   double non_young_end_time_sec = os::elapsedTime();
   _recorded_non_young_cset_choice_time_ms =
     (non_young_end_time_sec - non_young_start_time_sec) * 1000.0;
@@ -2914,12 +3031,6 @@
 }
 
 void G1CollectorPolicy_BestRegionsFirst::
-expand_if_possible(size_t numRegions) {
-  size_t expansion_bytes = numRegions * HeapRegion::GrainBytes;
-  _g1->expand(expansion_bytes);
-}
-
-void G1CollectorPolicy_BestRegionsFirst::
 record_collection_pause_end() {
   G1CollectorPolicy::record_collection_pause_end();
   assert(assertMarkedBytesDataOK(), "Marked regions not OK at pause end.");
--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Wed Sep 07 12:21:23 2011 -0400
@@ -493,7 +493,6 @@
 
   // </NEW PREDICTION>
 
-public:
   void cset_regions_freed() {
     bool propagate = _last_young_gc_full && !_in_marking_window;
     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
@@ -1045,7 +1044,7 @@
   // new cycle, as long as we are not already in one. It's best if it
   // is called during a safepoint when the test whether a cycle is in
   // progress or not is stable.
-  bool force_initial_mark_if_outside_cycle();
+  bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 
   // This is called at the very beginning of an evacuation pause (it
   // has to be the first thing that the pause does). If
@@ -1234,8 +1233,6 @@
 
 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
   CollectionSetChooser* _collectionSetChooser;
-  // If the estimated is less then desirable, resize if possible.
-  void expand_if_possible(size_t numRegions);
 
   virtual void choose_collection_set(double target_pause_time_ms);
   virtual void record_collection_pause_start(double start_time_sec,
@@ -1269,8 +1266,4 @@
   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 }
 
-// Local Variables: ***
-// c-indentation-style: gnu ***
-// End: ***
-
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1ErgoVerbose.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc_implementation/g1/g1ErgoVerbose.hpp"
+#include "utilities/ostream.hpp"
+
+ErgoLevel G1ErgoVerbose::_level;
+bool G1ErgoVerbose::_enabled[ErgoHeuristicNum];
+
+void G1ErgoVerbose::initialize() {
+  set_level(ErgoLow);
+  set_enabled(false);
+}
+
+void G1ErgoVerbose::set_level(ErgoLevel level) {
+  _level = level;
+}
+
+void G1ErgoVerbose::set_enabled(ErgoHeuristic n, bool enabled) {
+  assert(0 <= n && n < ErgoHeuristicNum, "pre-condition");
+  _enabled[n] = enabled;
+}
+
+void G1ErgoVerbose::set_enabled(bool enabled) {
+  for (int n = 0; n < ErgoHeuristicNum; n += 1) {
+    set_enabled((ErgoHeuristic) n, enabled);
+  }
+}
+
+const char* G1ErgoVerbose::to_string(int tag) {
+  ErgoHeuristic n = extract_heuristic(tag);
+  switch (n) {
+  case ErgoHeapSizing:            return "Heap Sizing";
+  case ErgoCSetConstruction:      return "CSet Construction";
+  case ErgoConcCycles:            return "Concurrent Cycles";
+  case ErgoPartiallyYoungGCs:     return "Partially-Young GCs";
+  default:
+    ShouldNotReachHere();
+    // Keep the Windows compiler happy
+    return NULL;
+  }
+}
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1ErgoVerbose.hpp	Wed Sep 07 12:21:23 2011 -0400
@@ -0,0 +1,197 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ERGOVERBOSE_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1ERGOVERBOSE_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/debug.hpp"
+
+// The log of G1's heuristic decisions comprises of a series of
+// records which have a similar format in order to maintain
+// consistency across records and ultimately easier parsing of the
+// output, if we ever choose to do that. Each record consists of:
+// * A time stamp to be able to easily correlate each record with
+// other events.
+// * A unique string to allow us to easily identify such records.
+// * The name of the heuristic the record corresponds to.
+// * An action string which describes the action that G1 did or is
+// about to do.
+// * An optional reason string which describes the reason for the
+// action.
+// * An optional number of name/value pairs which contributed to the
+// decision to take the action described in the record.
+//
+// Each record is associated with a "tag" which is the combination of
+// the heuristic the record corresponds to, as well as the min level
+// of verboseness at which the record should be printed. The tag is
+// checked against the current settings to determine whether the record
+// should be printed or not.
+
+// The available verboseness levels.
+typedef enum {
+  // Determine which part of the tag is occupied by the level.
+  ErgoLevelShift = 8,
+  ErgoLevelMask = ~((1 << ErgoLevelShift) - 1),
+
+  // ErgoLow is 0 so that we don't have to explicitly or a heuristic
+  // id with ErgoLow to keep its use simpler.
+  ErgoLow = 0,
+  ErgoHigh = 1 << ErgoLevelShift,
+} ErgoLevel;
+
+// The available heuristics.
+typedef enum {
+  // Determines which part of the tag is occupied by the heuristic id.
+  ErgoHeuristicMask = ~ErgoLevelMask,
+
+  ErgoHeapSizing = 0,
+  ErgoCSetConstruction,
+  ErgoConcCycles,
+  ErgoPartiallyYoungGCs,
+
+  ErgoHeuristicNum
+} ErgoHeuristic;
+
+class G1ErgoVerbose : AllStatic {
+private:
+  // Determines the minimum verboseness level at which records will be
+  // printed.
+  static ErgoLevel _level;
+  // Determines which heuristics are currently enabled.
+  static bool _enabled[ErgoHeuristicNum];
+
+  static ErgoLevel extract_level(int tag) {
+    return (ErgoLevel) (tag & ErgoLevelMask);
+  }
+
+  static ErgoHeuristic extract_heuristic(int tag) {
+    return (ErgoHeuristic) (tag & ErgoHeuristicMask);
+  }
+
+public:
+  // Needs to be explicitly called at GC initialization.
+  static void initialize();
+
+  static void set_level(ErgoLevel level);
+  static void set_enabled(ErgoHeuristic h, bool enabled);
+  // It is applied to all heuristics.
+  static void set_enabled(bool enabled);
+
+  static bool enabled(int tag) {
+    ErgoLevel level = extract_level(tag);
+    ErgoHeuristic n = extract_heuristic(tag);
+    return level <= _level && _enabled[n];
+  }
+
+  // Extract the heuristic id from the tag and return a string with
+  // its name.
+  static const char* to_string(int tag);
+};
+
+// The macros below generate the format string for values of different
+// types and/or metrics.
+
+// The reason for the action is optional and is handled specially: the
+// reason string is concatenated here so it's not necessary to pass it
+// as a parameter.
+#define ergo_format_reason(_reason_) ", reason: " _reason_
+
+// Single parameter format strings
+#define ergo_format_str(_name_)      ", " _name_ ": %s"
+#define ergo_format_region(_name_)   ", " _name_ ": "SIZE_FORMAT" regions"
+#define ergo_format_byte(_name_)     ", " _name_ ": "SIZE_FORMAT" bytes"
+#define ergo_format_double(_name_)   ", " _name_ ": %1.2f"
+#define ergo_format_perc(_name_)     ", " _name_ ": %1.2f %%"
+#define ergo_format_ms(_name_)       ", " _name_ ": %1.2f ms"
+
+// Double parameter format strings
+#define ergo_format_byte_perc(_name_)                                   \
+                             ", " _name_ ": "SIZE_FORMAT" bytes (%1.2f %%)"
+
+// Generates the format string
+#define ergo_format(_action_, _extra_format_)                   \
+  " %1.3f: [G1Ergonomics (%s) " _action_ _extra_format_ "]"
+
+// Conditionally, prints an ergonomic decision record. _extra_format_
+// is the format string for the optional items we'd like to print
+// (i.e., the decision's reason and any associated values). This
+// string should be built up using the ergo_*_format macros (see
+// above) to ensure consistency.
+//
+// Since we cannot rely on the compiler supporting variable argument
+// macros, this macro accepts a fixed number of arguments and passes
+// them to the print method. For convenience, we have wrapper macros
+// below which take a specific number of arguments and set the rest to
+// a default value.
+#define ergo_verbose_common(_tag_, _action_, _extra_format_,            \
+                            _arg0_, _arg1_, _arg2_, _arg3_, _arg4_, _arg5_) \
+  do {                                                                  \
+    if (G1ErgoVerbose::enabled((_tag_))) {                              \
+      gclog_or_tty->print_cr(ergo_format(_action_, _extra_format_),     \
+                             os::elapsedTime(),                         \
+                             G1ErgoVerbose::to_string((_tag_)),         \
+                             (_arg0_), (_arg1_), (_arg2_),              \
+                             (_arg3_), (_arg4_), (_arg5_));             \
+    }                                                                   \
+  } while (0)
+
+
+#define ergo_verbose(_tag_, _action_)                           \
+  ergo_verbose_common(_tag_, _action_, "", 0, 0, 0, 0, 0, 0)
+
+#define ergo_verbose0(_tag_, _action_, _extra_format_)                  \
+  ergo_verbose_common(_tag_, _action_, _extra_format_, 0, 0, 0, 0, 0, 0)
+
+#define ergo_verbose1(_tag_, _action_, _extra_format_,                  \
+                      _arg0_)                                           \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, 0, 0, 0, 0, 0)
+
+#define ergo_verbose2(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_)                                   \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, 0, 0, 0, 0)
+
+#define ergo_verbose3(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_)                           \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, 0, 0, 0)
+
+#define ergo_verbose4(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_)                   \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_, 0, 0)
+
+#define ergo_verbose5(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_, _arg4_)           \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_, _arg4_, 0)
+
+#define ergo_verbose6(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_, _arg4_, _arg5_)   \
+  ergo_verbose_common(_tag_, _action_, _extra_format_,                  \
+                      _arg0_, _arg1_, _arg2_, _arg3_, _arg4_, _arg5_)
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ERGOVERBOSE_HPP
--- a/src/share/vm/gc_implementation/g1/g1MMUTracker.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1MMUTracker.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -97,10 +97,6 @@
     // or performance (we are GC'ing most of the time anyway!),
     // simply overwrite the oldest entry in the tracker.
 
-    if (G1PolicyVerbose > 1) {
-      warning("MMU Tracker Queue overflow. Replacing earliest entry.");
-    }
-
     _head_index = trim_index(_head_index + 1);
     assert(_head_index == _tail_index, "Because we have a full circular buffer");
     _tail_index = trim_index(_tail_index + 1);
--- a/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp	Tue Sep 06 21:03:51 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp	Wed Sep 07 12:21:23 2011 -0400
@@ -98,7 +98,7 @@
 
     // At this point we are supposed to start a concurrent cycle. We
     // will do so if one is not already in progress.
-    bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle();
+    bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 
     // The above routine returns true if we were able to force the
     // next GC pause to be an initial mark; it returns false if a