changeset 2741:8229bd737950

7075646: G1: fix inconsistencies in the monitoring data Summary: Fixed a few inconsistencies in the monitoring data, in particular when reported from jstat. Reviewed-by: jmasa, brutisso, johnc
author tonyp
date Fri, 23 Sep 2011 16:07:49 -0400
parents 4dfb2df418f2
children e807478bf9ca
files src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp src/share/vm/gc_implementation/g1/g1MonitoringSupport.cpp src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp src/share/vm/gc_implementation/g1/heapRegion.hpp src/share/vm/gc_implementation/shared/generationCounters.cpp src/share/vm/gc_implementation/shared/generationCounters.hpp src/share/vm/services/g1MemoryPool.cpp src/share/vm/services/g1MemoryPool.hpp
diffstat 10 files changed, 423 insertions(+), 272 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Fri Sep 23 16:07:49 2011 -0400
@@ -816,6 +816,11 @@
     result =
       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
     assert(result != NULL, "it should always return a valid result");
+
+    // A successful humongous object allocation changes the used space
+    // information of the old generation so we need to recalculate the
+    // sizes and update the jstat counters here.
+    g1mm()->update_sizes();
   }
 
   verify_region_sets_optional();
@@ -1422,7 +1427,7 @@
   if (PrintHeapAtGC) {
     Universe::print_heap_after_gc();
   }
-  g1mm()->update_counters();
+  g1mm()->update_sizes();
   post_full_gc_dump();
 
   return true;
@@ -1790,6 +1795,7 @@
   _evac_failure_scan_stack(NULL) ,
   _mark_in_progress(false),
   _cg1r(NULL), _summary_bytes_used(0),
+  _g1mm(NULL),
   _refine_cte_cl(NULL),
   _full_collection(false),
   _free_list("Master Free List"),
@@ -2069,7 +2075,7 @@
 
   // Do create of the monitoring and management support so that
   // values in the heap have been properly initialized.
-  _g1mm = new G1MonitoringSupport(this, &_g1_storage);
+  _g1mm = new G1MonitoringSupport(this);
 
   return JNI_OK;
 }
@@ -3702,7 +3708,7 @@
   if (PrintHeapAtGC) {
     Universe::print_heap_after_gc();
   }
-  g1mm()->update_counters();
+  g1mm()->update_sizes();
 
   if (G1SummarizeRSetStats &&
       (G1SummarizeRSetStatsPeriod > 0) &&
@@ -5815,7 +5821,6 @@
       g1_policy()->update_region_num(true /* next_is_young */);
       set_region_short_lived_locked(new_alloc_region);
       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
-      g1mm()->update_eden_counters();
       return new_alloc_region;
     }
   }
@@ -5830,6 +5835,10 @@
   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
   _summary_bytes_used += allocated_bytes;
   _hr_printer.retire(alloc_region);
+  // We update the eden sizes here, when the region is retired,
+  // instead of when it's allocated, since this is the point that its
+  // used space has been recored in _summary_bytes_used.
+  g1mm()->update_eden_size();
 }
 
 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -597,7 +597,10 @@
 
 public:
 
-  G1MonitoringSupport* g1mm() { return _g1mm; }
+  G1MonitoringSupport* g1mm() {
+    assert(_g1mm != NULL, "should have been initialized");
+    return _g1mm;
+  }
 
   // Expand the garbage-first heap by at least the given size (in bytes!).
   // Returns true if the heap was expanded by the requested amount;
--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -1149,6 +1149,10 @@
     return young_list_length < young_list_max_length;
   }
 
+  size_t young_list_max_length() {
+    return _young_list_max_length;
+  }
+
   void update_region_num(bool young);
 
   bool full_young_gcs() {
--- a/src/share/vm/gc_implementation/g1/g1MonitoringSupport.cpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1MonitoringSupport.cpp	Fri Sep 23 16:07:49 2011 -0400
@@ -27,19 +27,69 @@
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
 
-G1MonitoringSupport::G1MonitoringSupport(G1CollectedHeap* g1h,
-                                         VirtualSpace* g1_storage_addr) :
+G1GenerationCounters::G1GenerationCounters(G1MonitoringSupport* g1mm,
+                                           const char* name,
+                                           int ordinal, int spaces,
+                                           size_t min_capacity,
+                                           size_t max_capacity,
+                                           size_t curr_capacity)
+  : GenerationCounters(name, ordinal, spaces, min_capacity,
+                       max_capacity, curr_capacity), _g1mm(g1mm) { }
+
+// We pad the capacity three times given that the young generation
+// contains three spaces (eden and two survivors).
+G1YoungGenerationCounters::G1YoungGenerationCounters(G1MonitoringSupport* g1mm,
+                                                     const char* name)
+  : G1GenerationCounters(g1mm, name, 0 /* ordinal */, 3 /* spaces */,
+               G1MonitoringSupport::pad_capacity(0, 3) /* min_capacity */,
+               G1MonitoringSupport::pad_capacity(g1mm->young_gen_max(), 3),
+               G1MonitoringSupport::pad_capacity(0, 3) /* curr_capacity */) {
+  update_all();
+}
+
+G1OldGenerationCounters::G1OldGenerationCounters(G1MonitoringSupport* g1mm,
+                                                 const char* name)
+  : G1GenerationCounters(g1mm, name, 1 /* ordinal */, 1 /* spaces */,
+               G1MonitoringSupport::pad_capacity(0) /* min_capacity */,
+               G1MonitoringSupport::pad_capacity(g1mm->old_gen_max()),
+               G1MonitoringSupport::pad_capacity(0) /* curr_capacity */) {
+  update_all();
+}
+
+void G1YoungGenerationCounters::update_all() {
+  size_t committed =
+            G1MonitoringSupport::pad_capacity(_g1mm->young_gen_committed(), 3);
+  _current_size->set_value(committed);
+}
+
+void G1OldGenerationCounters::update_all() {
+  size_t committed =
+            G1MonitoringSupport::pad_capacity(_g1mm->old_gen_committed());
+  _current_size->set_value(committed);
+}
+
+G1MonitoringSupport::G1MonitoringSupport(G1CollectedHeap* g1h) :
   _g1h(g1h),
   _incremental_collection_counters(NULL),
   _full_collection_counters(NULL),
-  _non_young_collection_counters(NULL),
+  _old_collection_counters(NULL),
   _old_space_counters(NULL),
   _young_collection_counters(NULL),
   _eden_counters(NULL),
   _from_counters(NULL),
   _to_counters(NULL),
-  _g1_storage_addr(g1_storage_addr)
-{
+
+  _overall_reserved(0),
+  _overall_committed(0),    _overall_used(0),
+  _young_region_num(0),
+  _young_gen_committed(0),
+  _eden_committed(0),       _eden_used(0),
+  _survivor_committed(0),   _survivor_used(0),
+  _old_committed(0),        _old_used(0) {
+
+  _overall_reserved = g1h->max_capacity();
+  recalculate_sizes();
+
   // Counters for GC collections
   //
   //  name "collector.0".  In a generational collector this would be the
@@ -69,110 +119,147 @@
   // generational GC terms.  The "1, 1" parameters are for
   // the n-th generation (=1) with 1 space.
   // Counters are created from minCapacity, maxCapacity, and capacity
-  _non_young_collection_counters =
-    new GenerationCounters("whole heap", 1, 1, _g1_storage_addr);
+  _old_collection_counters = new G1OldGenerationCounters(this, "old");
 
   //  name  "generation.1.space.0"
   // Counters are created from maxCapacity, capacity, initCapacity,
   // and used.
-  _old_space_counters = new HSpaceCounters("space", 0,
-    _g1h->max_capacity(), _g1h->capacity(), _non_young_collection_counters);
+  _old_space_counters = new HSpaceCounters("space", 0 /* ordinal */,
+    pad_capacity(overall_reserved()) /* max_capacity */,
+    pad_capacity(old_space_committed()) /* init_capacity */,
+   _old_collection_counters);
 
   //   Young collection set
   //  name "generation.0".  This is logically the young generation.
   //  The "0, 3" are paremeters for the n-th genertaion (=0) with 3 spaces.
-  // See  _non_young_collection_counters for additional counters
-  _young_collection_counters = new GenerationCounters("young", 0, 3, NULL);
+  // See  _old_collection_counters for additional counters
+  _young_collection_counters = new G1YoungGenerationCounters(this, "young");
 
-  // Replace "max_heap_byte_size() with maximum young gen size for
-  // g1Collectedheap
   //  name "generation.0.space.0"
   // See _old_space_counters for additional counters
-  _eden_counters = new HSpaceCounters("eden", 0,
-    _g1h->max_capacity(), eden_space_committed(),
+  _eden_counters = new HSpaceCounters("eden", 0 /* ordinal */,
+    pad_capacity(overall_reserved()) /* max_capacity */,
+    pad_capacity(eden_space_committed()) /* init_capacity */,
     _young_collection_counters);
 
   //  name "generation.0.space.1"
   // See _old_space_counters for additional counters
   // Set the arguments to indicate that this survivor space is not used.
-  _from_counters = new HSpaceCounters("s0", 1, (long) 0, (long) 0,
+  _from_counters = new HSpaceCounters("s0", 1 /* ordinal */,
+    pad_capacity(0) /* max_capacity */,
+    pad_capacity(0) /* init_capacity */,
     _young_collection_counters);
+  // Given that this survivor space is not used, we update it here
+  // once to reflect that its used space is 0 so that we don't have to
+  // worry about updating it again later.
+  _from_counters->update_used(0);
 
   //  name "generation.0.space.2"
   // See _old_space_counters for additional counters
-  _to_counters = new HSpaceCounters("s1", 2,
-    _g1h->max_capacity(),
-    survivor_space_committed(),
+  _to_counters = new HSpaceCounters("s1", 2 /* ordinal */,
+    pad_capacity(overall_reserved()) /* max_capacity */,
+    pad_capacity(survivor_space_committed()) /* init_capacity */,
     _young_collection_counters);
 }
 
-size_t G1MonitoringSupport::overall_committed() {
-  return g1h()->capacity();
+void G1MonitoringSupport::recalculate_sizes() {
+  G1CollectedHeap* g1 = g1h();
+
+  // Recalculate all the sizes from scratch. We assume that this is
+  // called at a point where no concurrent updates to the various
+  // values we read here are possible (i.e., at a STW phase at the end
+  // of a GC).
+
+  size_t young_list_length = g1->young_list()->length();
+  size_t survivor_list_length = g1->g1_policy()->recorded_survivor_regions();
+  assert(young_list_length >= survivor_list_length, "invariant");
+  size_t eden_list_length = young_list_length - survivor_list_length;
+  // Max length includes any potential extensions to the young gen
+  // we'll do when the GC locker is active.
+  size_t young_list_max_length = g1->g1_policy()->young_list_max_length();
+  assert(young_list_max_length >= survivor_list_length, "invariant");
+  size_t eden_list_max_length = young_list_max_length - survivor_list_length;
+
+  _overall_used = g1->used_unlocked();
+  _eden_used = eden_list_length * HeapRegion::GrainBytes;
+  _survivor_used = survivor_list_length * HeapRegion::GrainBytes;
+  _young_region_num = young_list_length;
+  _old_used = subtract_up_to_zero(_overall_used, _eden_used + _survivor_used);
+
+  // First calculate the committed sizes that can be calculated independently.
+  _survivor_committed = _survivor_used;
+  _old_committed = HeapRegion::align_up_to_region_byte_size(_old_used);
+
+  // Next, start with the overall committed size.
+  _overall_committed = g1->capacity();
+  size_t committed = _overall_committed;
+
+  // Remove the committed size we have calculated so far (for the
+  // survivor and old space).
+  assert(committed >= (_survivor_committed + _old_committed), "sanity");
+  committed -= _survivor_committed + _old_committed;
+
+  // Next, calculate and remove the committed size for the eden.
+  _eden_committed = eden_list_max_length * HeapRegion::GrainBytes;
+  // Somewhat defensive: be robust in case there are inaccuracies in
+  // the calculations
+  _eden_committed = MIN2(_eden_committed, committed);
+  committed -= _eden_committed;
+
+  // Finally, give the rest to the old space...
+  _old_committed += committed;
+  // ..and calculate the young gen committed.
+  _young_gen_committed = _eden_committed + _survivor_committed;
+
+  assert(_overall_committed ==
+         (_eden_committed + _survivor_committed + _old_committed),
+         "the committed sizes should add up");
+  // Somewhat defensive: cap the eden used size to make sure it
+  // never exceeds the committed size.
+  _eden_used = MIN2(_eden_used, _eden_committed);
+  // _survivor_committed and _old_committed are calculated in terms of
+  // the corresponding _*_used value, so the next two conditions
+  // should hold.
+  assert(_survivor_used <= _survivor_committed, "post-condition");
+  assert(_old_used <= _old_committed, "post-condition");
 }
 
-size_t G1MonitoringSupport::overall_used() {
-  return g1h()->used_unlocked();
-}
+void G1MonitoringSupport::recalculate_eden_size() {
+  G1CollectedHeap* g1 = g1h();
 
-size_t G1MonitoringSupport::eden_space_committed() {
-  return MAX2(eden_space_used(), (size_t) HeapRegion::GrainBytes);
-}
+  // When a new eden region is allocated, only the eden_used size is
+  // affected (since we have recalculated everything else at the last GC).
 
-size_t G1MonitoringSupport::eden_space_used() {
-  size_t young_list_length = g1h()->young_list()->length();
-  size_t eden_used = young_list_length * HeapRegion::GrainBytes;
-  size_t survivor_used = survivor_space_used();
-  eden_used = subtract_up_to_zero(eden_used, survivor_used);
-  return eden_used;
-}
-
-size_t G1MonitoringSupport::survivor_space_committed() {
-  return MAX2(survivor_space_used(),
-              (size_t) HeapRegion::GrainBytes);
-}
-
-size_t G1MonitoringSupport::survivor_space_used() {
-  size_t survivor_num = g1h()->g1_policy()->recorded_survivor_regions();
-  size_t survivor_used = survivor_num * HeapRegion::GrainBytes;
-  return survivor_used;
-}
-
-size_t G1MonitoringSupport::old_space_committed() {
-  size_t committed = overall_committed();
-  size_t eden_committed = eden_space_committed();
-  size_t survivor_committed = survivor_space_committed();
-  committed = subtract_up_to_zero(committed, eden_committed);
-  committed = subtract_up_to_zero(committed, survivor_committed);
-  committed = MAX2(committed, (size_t) HeapRegion::GrainBytes);
-  return committed;
-}
-
-// See the comment near the top of g1MonitoringSupport.hpp for
-// an explanation of these calculations for "used" and "capacity".
-size_t G1MonitoringSupport::old_space_used() {
-  size_t used = overall_used();
-  size_t eden_used = eden_space_used();
-  size_t survivor_used = survivor_space_used();
-  used = subtract_up_to_zero(used, eden_used);
-  used = subtract_up_to_zero(used, survivor_used);
-  return used;
-}
-
-void G1MonitoringSupport::update_counters() {
-  if (UsePerfData) {
-    eden_counters()->update_capacity(eden_space_committed());
-    eden_counters()->update_used(eden_space_used());
-    to_counters()->update_capacity(survivor_space_committed());
-    to_counters()->update_used(survivor_space_used());
-    old_space_counters()->update_capacity(old_space_committed());
-    old_space_counters()->update_used(old_space_used());
-    non_young_collection_counters()->update_all();
+  size_t young_region_num = g1h()->young_list()->length();
+  if (young_region_num > _young_region_num) {
+    size_t diff = young_region_num - _young_region_num;
+    _eden_used += diff * HeapRegion::GrainBytes;
+    // Somewhat defensive: cap the eden used size to make sure it
+    // never exceeds the committed size.
+    _eden_used = MIN2(_eden_used, _eden_committed);
+    _young_region_num = young_region_num;
   }
 }
 
-void G1MonitoringSupport::update_eden_counters() {
+void G1MonitoringSupport::update_sizes() {
+  recalculate_sizes();
   if (UsePerfData) {
-    eden_counters()->update_capacity(eden_space_committed());
+    eden_counters()->update_capacity(pad_capacity(eden_space_committed()));
+    eden_counters()->update_used(eden_space_used());
+    // only the to survivor space (s1) is active, so we don't need to
+    // update the counteres for the from survivor space (s0)
+    to_counters()->update_capacity(pad_capacity(survivor_space_committed()));
+    to_counters()->update_used(survivor_space_used());
+    old_space_counters()->update_capacity(pad_capacity(old_space_committed()));
+    old_space_counters()->update_used(old_space_used());
+    old_collection_counters()->update_all();
+    young_collection_counters()->update_all();
+  }
+}
+
+void G1MonitoringSupport::update_eden_size() {
+  recalculate_eden_size();
+  if (UsePerfData) {
     eden_counters()->update_used(eden_space_used());
   }
 }
--- a/src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -28,101 +28,93 @@
 #include "gc_implementation/shared/hSpaceCounters.hpp"
 
 class G1CollectedHeap;
-class G1SpaceMonitoringSupport;
 
-// Class for monitoring logical spaces in G1.
-// G1 defines a set of regions as a young
-// collection (analogous to a young generation).
-// The young collection is a logical generation
-// with no fixed chunk (see space.hpp) reflecting
-// the address space for the generation.  In addition
-// to the young collection there is its complement
-// the non-young collection that is simply the regions
-// not in the young collection.  The non-young collection
-// is treated here as a logical old generation only
-// because the monitoring tools expect a generational
-// heap.  The monitoring tools expect that a Space
-// (see space.hpp) exists that describe the
-// address space of young collection and non-young
-// collection and such a view is provided here.
+// Class for monitoring logical spaces in G1. It provides data for
+// both G1's jstat counters as well as G1's memory pools.
 //
-// This class provides interfaces to access
-// the value of variables for the young collection
-// that include the "capacity" and "used" of the
-// young collection along with constant values
-// for the minimum and maximum capacities for
-// the logical spaces.  Similarly for the non-young
-// collection.
+// G1 splits the heap into heap regions and each heap region belongs
+// to one of the following categories:
 //
-// Also provided are counters for G1 concurrent collections
-// and stop-the-world full heap collecitons.
+// * eden      : regions that have been allocated since the last GC
+// * survivors : regions with objects that survived the last few GCs
+// * old       : long-lived non-humongous regions
+// * humongous : humongous regions
+// * free      : free regions
 //
-// Below is a description of how "used" and "capactiy"
-// (or committed) is calculated for the logical spaces.
+// The combination of eden and survivor regions form the equivalent of
+// the young generation in the other GCs. The combination of old and
+// humongous regions form the equivalent of the old generation in the
+// other GCs. Free regions do not have a good equivalent in the other
+// GCs given that they can be allocated as any of the other region types.
 //
-// 1) The used space calculation for a pool is not necessarily
-// independent of the others. We can easily get from G1 the overall
-// used space in the entire heap, the number of regions in the young
-// generation (includes both eden and survivors), and the number of
-// survivor regions. So, from that we calculate:
+// The monitoring tools expect the heap to contain a number of
+// generations (young, old, perm) and each generation to contain a
+// number of spaces (young: eden, survivors, old). Given that G1 does
+// not maintain those spaces physically (e.g., the set of
+// non-contiguous eden regions can be considered as a "logical"
+// space), we'll provide the illusion that those generations and
+// spaces exist. In reality, each generation and space refers to a set
+// of heap regions that are potentially non-contiguous.
 //
-//  survivor_used = survivor_num * region_size
-//  eden_used     = young_region_num * region_size - survivor_used
-//  old_gen_used  = overall_used - eden_used - survivor_used
+// This class provides interfaces to access the min, current, and max
+// capacity and current occupancy for each of G1's logical spaces and
+// generations we expose to the monitoring tools. Also provided are
+// counters for G1 concurrent collections and stop-the-world full heap
+// collections.
 //
-// Note that survivor_used and eden_used are upper bounds. To get the
-// actual value we would have to iterate over the regions and add up
-// ->used(). But that'd be expensive. So, we'll accept some lack of
-// accuracy for those two. But, we have to be careful when calculating
-// old_gen_used, in case we subtract from overall_used more then the
-// actual number and our result goes negative.
+// Below is a description of how the various sizes are calculated.
 //
-// 2) Calculating the used space is straightforward, as described
-// above. However, how do we calculate the committed space, given that
-// we allocate space for the eden, survivor, and old gen out of the
-// same pool of regions? One way to do this is to use the used value
-// as also the committed value for the eden and survivor spaces and
-// then calculate the old gen committed space as follows:
+// * Current Capacity
 //
-//  old_gen_committed = overall_committed - eden_committed - survivor_committed
+//    - heap_capacity = current heap capacity (e.g., current committed size)
+//    - young_gen_capacity = current max young gen target capacity
+//          (i.e., young gen target capacity + max allowed expansion capacity)
+//    - survivor_capacity = current survivor region capacity
+//    - eden_capacity = young_gen_capacity - survivor_capacity
+//    - old_capacity = heap_capacity - young_gen_capacity
 //
-// Maybe a better way to do that would be to calculate used for eden
-// and survivor as a sum of ->used() over their regions and then
-// calculate committed as region_num * region_size (i.e., what we use
-// to calculate the used space now). This is something to consider
-// in the future.
+//    What we do in the above is to distribute the free regions among
+//    eden_capacity and old_capacity.
 //
-// 3) Another decision that is again not straightforward is what is
-// the max size that each memory pool can grow to. One way to do this
-// would be to use the committed size for the max for the eden and
-// survivors and calculate the old gen max as follows (basically, it's
-// a similar pattern to what we use for the committed space, as
-// described above):
+// * Occupancy
 //
-//  old_gen_max = overall_max - eden_max - survivor_max
+//    - young_gen_used = current young region capacity
+//    - survivor_used = survivor_capacity
+//    - eden_used = young_gen_used - survivor_used
+//    - old_used = overall_used - young_gen_used
 //
-// Unfortunately, the above makes the max of each pool fluctuate over
-// time and, even though this is allowed according to the spec, it
-// broke several assumptions in the M&M framework (there were cases
-// where used would reach a value greater than max). So, for max we
-// use -1, which means "undefined" according to the spec.
+//    Unfortunately, we currently only keep track of the number of
+//    currently allocated young and survivor regions + the overall used
+//    bytes in the heap, so the above can be a little inaccurate.
 //
-// 4) Now, there is a very subtle issue with all the above. The
-// framework will call get_memory_usage() on the three pools
-// asynchronously. As a result, each call might get a different value
-// for, say, survivor_num which will yield inconsistent values for
-// eden_used, survivor_used, and old_gen_used (as survivor_num is used
-// in the calculation of all three). This would normally be
-// ok. However, it's possible that this might cause the sum of
-// eden_used, survivor_used, and old_gen_used to go over the max heap
-// size and this seems to sometimes cause JConsole (and maybe other
-// clients) to get confused. There's not a really an easy / clean
-// solution to this problem, due to the asynchrounous nature of the
-// framework.
+// * Min Capacity
+//
+//    We set this to 0 for all spaces. We could consider setting the old
+//    min capacity to the min capacity of the heap (see 7078465).
+//
+// * Max Capacity
+//
+//    For jstat, we set the max capacity of all spaces to heap_capacity,
+//    given that we don't always have a reasonably upper bound on how big
+//    each space can grow. For the memory pools, we actually make the max
+//    capacity undefined. We could consider setting the old max capacity
+//    to the max capacity of the heap (see 7078465).
+//
+// If we had more accurate occupancy / capacity information per
+// region set the above calculations would be greatly simplified and
+// be made more accurate.
+//
+// We update all the above synchronously and we store the results in
+// fields so that we just read said fields when needed. A subtle point
+// is that all the above sizes need to be recalculated when the old
+// gen changes capacity (after a GC or after a humongous allocation)
+// but only the eden occupancy changes when a new eden region is
+// allocated. So, in the latter case we have minimal recalcuation to
+// do which is important as we want to keep the eden region allocation
+// path as low-overhead as possible.
 
 class G1MonitoringSupport : public CHeapObj {
   G1CollectedHeap* _g1h;
-  VirtualSpace* _g1_storage_addr;
 
   // jstat performance counters
   //  incremental collections both fully and partially young
@@ -133,9 +125,9 @@
   // _from_counters, and _to_counters are associated with
   // this "generational" counter.
   GenerationCounters*  _young_collection_counters;
-  //  non-young collection set counters. The _old_space_counters
+  //  old collection set counters. The _old_space_counters
   // below are associated with this "generational" counter.
-  GenerationCounters*  _non_young_collection_counters;
+  GenerationCounters*  _old_collection_counters;
   // Counters for the capacity and used for
   //   the whole heap
   HSpaceCounters*      _old_space_counters;
@@ -145,6 +137,27 @@
   HSpaceCounters*      _from_counters;
   HSpaceCounters*      _to_counters;
 
+  // When it's appropriate to recalculate the various sizes (at the
+  // end of a GC, when a new eden region is allocated, etc.) we store
+  // them here so that we can easily report them when needed and not
+  // have to recalculate them every time.
+
+  size_t _overall_reserved;
+  size_t _overall_committed;
+  size_t _overall_used;
+
+  size_t _young_region_num;
+  size_t _young_gen_committed;
+  size_t _eden_committed;
+  size_t _eden_used;
+  size_t _survivor_committed;
+  size_t _survivor_used;
+
+  size_t _old_committed;
+  size_t _old_used;
+
+  G1CollectedHeap* g1h() { return _g1h; }
+
   // It returns x - y if x > y, 0 otherwise.
   // As described in the comment above, some of the inputs to the
   // calculations we have to do are obtained concurrently and hence
@@ -160,15 +173,35 @@
     }
   }
 
+  // Recalculate all the sizes.
+  void recalculate_sizes();
+  // Recalculate only what's necessary when a new eden region is allocated.
+  void recalculate_eden_size();
+
  public:
-  G1MonitoringSupport(G1CollectedHeap* g1h, VirtualSpace* g1_storage_addr);
+  G1MonitoringSupport(G1CollectedHeap* g1h);
 
-  G1CollectedHeap* g1h() { return _g1h; }
-  VirtualSpace* g1_storage_addr() { return _g1_storage_addr; }
+  // Unfortunately, the jstat tool assumes that no space has 0
+  // capacity. In our case, given that each space is logical, it's
+  // possible that no regions will be allocated to it, hence to have 0
+  // capacity (e.g., if there are no survivor regions, the survivor
+  // space has 0 capacity). The way we deal with this is to always pad
+  // each capacity value we report to jstat by a very small amount to
+  // make sure that it's never zero. Given that we sometimes have to
+  // report a capacity of a generation that contains several spaces
+  // (e.g., young gen includes one eden, two survivor spaces), the
+  // mult parameter is provided in order to adding the appropriate
+  // padding multiple times so that the capacities add up correctly.
+  static size_t pad_capacity(size_t size_bytes, size_t mult = 1) {
+    return size_bytes + MinObjAlignmentInBytes * mult;
+  }
 
-  // Performance Counter accessors
-  void update_counters();
-  void update_eden_counters();
+  // Recalculate all the sizes from scratch and update all the jstat
+  // counters accordingly.
+  void update_sizes();
+  // Recalculate only what's necessary when a new eden region is
+  // allocated and update any jstat counters that need to be updated.
+  void update_eden_size();
 
   CollectorCounters* incremental_collection_counters() {
     return _incremental_collection_counters;
@@ -176,8 +209,11 @@
   CollectorCounters* full_collection_counters() {
     return _full_collection_counters;
   }
-  GenerationCounters* non_young_collection_counters() {
-    return _non_young_collection_counters;
+  GenerationCounters* young_collection_counters() {
+    return _young_collection_counters;
+  }
+  GenerationCounters* old_collection_counters() {
+    return _old_collection_counters;
   }
   HSpaceCounters*      old_space_counters() { return _old_space_counters; }
   HSpaceCounters*      eden_counters() { return _eden_counters; }
@@ -187,17 +223,45 @@
   // Monitoring support used by
   //   MemoryService
   //   jstat counters
-  size_t overall_committed();
-  size_t overall_used();
 
-  size_t eden_space_committed();
-  size_t eden_space_used();
+  size_t overall_reserved()           { return _overall_reserved;     }
+  size_t overall_committed()          { return _overall_committed;    }
+  size_t overall_used()               { return _overall_used;         }
 
-  size_t survivor_space_committed();
-  size_t survivor_space_used();
+  size_t young_gen_committed()        { return _young_gen_committed;  }
+  size_t young_gen_max()              { return overall_reserved();    }
+  size_t eden_space_committed()       { return _eden_committed;       }
+  size_t eden_space_used()            { return _eden_used;            }
+  size_t survivor_space_committed()   { return _survivor_committed;   }
+  size_t survivor_space_used()        { return _survivor_used;        }
 
-  size_t old_space_committed();
-  size_t old_space_used();
+  size_t old_gen_committed()          { return old_space_committed(); }
+  size_t old_gen_max()                { return overall_reserved();    }
+  size_t old_space_committed()        { return _old_committed;        }
+  size_t old_space_used()             { return _old_used;             }
+};
+
+class G1GenerationCounters: public GenerationCounters {
+protected:
+  G1MonitoringSupport* _g1mm;
+
+public:
+  G1GenerationCounters(G1MonitoringSupport* g1mm,
+                       const char* name, int ordinal, int spaces,
+                       size_t min_capacity, size_t max_capacity,
+                       size_t curr_capacity);
+};
+
+class G1YoungGenerationCounters: public G1GenerationCounters {
+public:
+  G1YoungGenerationCounters(G1MonitoringSupport* g1mm, const char* name);
+  virtual void update_all();
+};
+
+class G1OldGenerationCounters: public G1GenerationCounters {
+public:
+  G1OldGenerationCounters(G1MonitoringSupport* g1mm, const char* name);
+  virtual void update_all();
 };
 
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP
--- a/src/share/vm/gc_implementation/g1/heapRegion.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/g1/heapRegion.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -357,6 +357,11 @@
   static int GrainWords;
   static int CardsPerRegion;
 
+  static size_t align_up_to_region_byte_size(size_t sz) {
+    return (sz + (size_t) GrainBytes - 1) &
+                                      ~((1 << (size_t) LogOfHRGrainBytes) - 1);
+  }
+
   // It sets up the heap region size (GrainBytes / GrainWords), as
   // well as other related fields that are based on the heap region
   // size (LogOfHRGrainBytes / LogOfHRGrainWords /
--- a/src/share/vm/gc_implementation/shared/generationCounters.cpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/shared/generationCounters.cpp	Fri Sep 23 16:07:49 2011 -0400
@@ -26,14 +26,10 @@
 #include "gc_implementation/shared/generationCounters.hpp"
 #include "memory/resourceArea.hpp"
 
-
-GenerationCounters::GenerationCounters(const char* name,
-                                       int ordinal, int spaces,
-                                       VirtualSpace* v):
-                    _virtual_space(v) {
-
+void GenerationCounters::initialize(const char* name, int ordinal, int spaces,
+                                    size_t min_capacity, size_t max_capacity,
+                                    size_t curr_capacity) {
   if (UsePerfData) {
-
     EXCEPTION_MARK;
     ResourceMark rm;
 
@@ -51,18 +47,37 @@
 
     cname = PerfDataManager::counter_name(_name_space, "minCapacity");
     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_Bytes,
-                                     _virtual_space == NULL ? 0 :
-                                     _virtual_space->committed_size(), CHECK);
+                                     min_capacity, CHECK);
 
     cname = PerfDataManager::counter_name(_name_space, "maxCapacity");
     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_Bytes,
-                                     _virtual_space == NULL ? 0 :
-                                     _virtual_space->reserved_size(), CHECK);
+                                     max_capacity, CHECK);
 
     cname = PerfDataManager::counter_name(_name_space, "capacity");
-    _current_size = PerfDataManager::create_variable(SUN_GC, cname,
-                                     PerfData::U_Bytes,
-                                     _virtual_space == NULL ? 0 :
-                                     _virtual_space->committed_size(), CHECK);
+    _current_size =
+      PerfDataManager::create_variable(SUN_GC, cname, PerfData::U_Bytes,
+                                       curr_capacity, CHECK);
   }
 }
+
+GenerationCounters::GenerationCounters(const char* name,
+                                       int ordinal, int spaces,
+                                       VirtualSpace* v)
+  : _virtual_space(v) {
+  assert(v != NULL, "don't call this constructor if v == NULL");
+  initialize(name, ordinal, spaces,
+             v->committed_size(), v->reserved_size(), v->committed_size());
+}
+
+GenerationCounters::GenerationCounters(const char* name,
+                                       int ordinal, int spaces,
+                                       size_t min_capacity, size_t max_capacity,
+                                       size_t curr_capacity)
+  : _virtual_space(NULL) {
+  initialize(name, ordinal, spaces, min_capacity, max_capacity, curr_capacity);
+}
+
+void GenerationCounters::update_all() {
+  assert(_virtual_space != NULL, "otherwise, override this method");
+  _current_size->set_value(_virtual_space->committed_size());
+}
--- a/src/share/vm/gc_implementation/shared/generationCounters.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/gc_implementation/shared/generationCounters.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -34,6 +34,11 @@
 class GenerationCounters: public CHeapObj {
   friend class VMStructs;
 
+private:
+  void initialize(const char* name, int ordinal, int spaces,
+                  size_t min_capacity, size_t max_capacity,
+                  size_t curr_capacity);
+
  protected:
   PerfVariable*      _current_size;
   VirtualSpace*      _virtual_space;
@@ -48,11 +53,18 @@
   char*              _name_space;
 
   // This constructor is only meant for use with the PSGenerationCounters
-  // constructor.  The need for such an constructor should be eliminated
+  // constructor. The need for such an constructor should be eliminated
   // when VirtualSpace and PSVirtualSpace are unified.
-  GenerationCounters() : _name_space(NULL), _current_size(NULL), _virtual_space(NULL) {}
+  GenerationCounters()
+             : _name_space(NULL), _current_size(NULL), _virtual_space(NULL) {}
+
+  // This constructor is used for subclasses that do not have a space
+  // associated with them (e.g, in G1).
+  GenerationCounters(const char* name, int ordinal, int spaces,
+                     size_t min_capacity, size_t max_capacity,
+                     size_t curr_capacity);
+
  public:
-
   GenerationCounters(const char* name, int ordinal, int spaces,
                      VirtualSpace* v);
 
@@ -60,10 +72,7 @@
     if (_name_space != NULL) FREE_C_HEAP_ARRAY(char, _name_space);
   }
 
-  virtual void update_all() {
-    _current_size->set_value(_virtual_space == NULL ? 0 :
-                             _virtual_space->committed_size());
-  }
+  virtual void update_all();
 
   const char* name_space() const        { return _name_space; }
 
--- a/src/share/vm/services/g1MemoryPool.cpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/services/g1MemoryPool.cpp	Fri Sep 23 16:07:49 2011 -0400
@@ -32,56 +32,28 @@
 G1MemoryPoolSuper::G1MemoryPoolSuper(G1CollectedHeap* g1h,
                                      const char* name,
                                      size_t init_size,
+                                     size_t max_size,
                                      bool support_usage_threshold) :
-  _g1h(g1h), CollectedMemoryPool(name,
-                                   MemoryPool::Heap,
-                                   init_size,
-                                   undefined_max(),
-                                   support_usage_threshold) {
+  _g1mm(g1h->g1mm()), CollectedMemoryPool(name,
+                                          MemoryPool::Heap,
+                                          init_size,
+                                          max_size,
+                                          support_usage_threshold) {
   assert(UseG1GC, "sanity");
 }
 
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::eden_space_committed(G1CollectedHeap* g1h) {
-  return MAX2(eden_space_used(g1h), (size_t) HeapRegion::GrainBytes);
-}
-
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::eden_space_used(G1CollectedHeap* g1h) {
-  return g1h->g1mm()->eden_space_used();
-}
-
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::survivor_space_committed(G1CollectedHeap* g1h) {
-  return g1h->g1mm()->survivor_space_committed();
-}
-
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::survivor_space_used(G1CollectedHeap* g1h) {
-  return g1h->g1mm()->survivor_space_used();
-}
-
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::old_space_committed(G1CollectedHeap* g1h) {
-  return g1h->g1mm()->old_space_committed();
-}
-
-// See the comment at the top of g1MemoryPool.hpp
-size_t G1MemoryPoolSuper::old_space_used(G1CollectedHeap* g1h) {
-  return g1h->g1mm()->old_space_used();
-}
-
 G1EdenPool::G1EdenPool(G1CollectedHeap* g1h) :
   G1MemoryPoolSuper(g1h,
                     "G1 Eden Space",
-                    eden_space_committed(g1h), /* init_size */
+                    g1h->g1mm()->eden_space_committed(), /* init_size */
+                    _undefined_max,
                     false /* support_usage_threshold */) { }
 
 MemoryUsage G1EdenPool::get_memory_usage() {
   size_t initial_sz = initial_size();
   size_t max_sz     = max_size();
   size_t used       = used_in_bytes();
-  size_t committed  = eden_space_committed(_g1h);
+  size_t committed  = _g1mm->eden_space_committed();
 
   return MemoryUsage(initial_sz, used, committed, max_sz);
 }
@@ -89,14 +61,15 @@
 G1SurvivorPool::G1SurvivorPool(G1CollectedHeap* g1h) :
   G1MemoryPoolSuper(g1h,
                     "G1 Survivor Space",
-                    survivor_space_committed(g1h), /* init_size */
+                    g1h->g1mm()->survivor_space_committed(), /* init_size */
+                    _undefined_max,
                     false /* support_usage_threshold */) { }
 
 MemoryUsage G1SurvivorPool::get_memory_usage() {
   size_t initial_sz = initial_size();
   size_t max_sz     = max_size();
   size_t used       = used_in_bytes();
-  size_t committed  = survivor_space_committed(_g1h);
+  size_t committed  = _g1mm->survivor_space_committed();
 
   return MemoryUsage(initial_sz, used, committed, max_sz);
 }
@@ -104,14 +77,15 @@
 G1OldGenPool::G1OldGenPool(G1CollectedHeap* g1h) :
   G1MemoryPoolSuper(g1h,
                     "G1 Old Gen",
-                    old_space_committed(g1h), /* init_size */
+                    g1h->g1mm()->old_space_committed(), /* init_size */
+                    _undefined_max,
                     true /* support_usage_threshold */) { }
 
 MemoryUsage G1OldGenPool::get_memory_usage() {
   size_t initial_sz = initial_size();
   size_t max_sz     = max_size();
   size_t used       = used_in_bytes();
-  size_t committed  = old_space_committed(_g1h);
+  size_t committed  = _g1mm->old_space_committed();
 
   return MemoryUsage(initial_sz, used, committed, max_sz);
 }
--- a/src/share/vm/services/g1MemoryPool.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/src/share/vm/services/g1MemoryPool.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -26,12 +26,11 @@
 #define SHARE_VM_SERVICES_G1MEMORYPOOL_HPP
 
 #ifndef SERIALGC
+#include "gc_implementation/g1/g1MonitoringSupport.hpp"
 #include "services/memoryPool.hpp"
 #include "services/memoryUsage.hpp"
 #endif
 
-class G1CollectedHeap;
-
 // This file contains the three classes that represent the memory
 // pools of the G1 spaces: G1EdenPool, G1SurvivorPool, and
 // G1OldGenPool. In G1, unlike our other GCs, we do not have a
@@ -50,37 +49,19 @@
 // on this model.
 //
 
-
 // This class is shared by the three G1 memory pool classes
-// (G1EdenPool, G1SurvivorPool, G1OldGenPool). Given that the way we
-// calculate used / committed bytes for these three pools is related
-// (see comment above), we put the calculations in this class so that
-// we can easily share them among the subclasses.
+// (G1EdenPool, G1SurvivorPool, G1OldGenPool).
 class G1MemoryPoolSuper : public CollectedMemoryPool {
 protected:
-  G1CollectedHeap* _g1h;
+  const static size_t _undefined_max = (size_t) -1;
+  G1MonitoringSupport* _g1mm;
 
   // Would only be called from subclasses.
   G1MemoryPoolSuper(G1CollectedHeap* g1h,
                     const char* name,
                     size_t init_size,
+                    size_t max_size,
                     bool support_usage_threshold);
-
-  // The reason why all the code is in static methods is so that it
-  // can be safely called from the constructors of the subclasses.
-
-  static size_t undefined_max() {
-    return (size_t) -1;
-  }
-
-  static size_t eden_space_committed(G1CollectedHeap* g1h);
-  static size_t eden_space_used(G1CollectedHeap* g1h);
-
-  static size_t survivor_space_committed(G1CollectedHeap* g1h);
-  static size_t survivor_space_used(G1CollectedHeap* g1h);
-
-  static size_t old_space_committed(G1CollectedHeap* g1h);
-  static size_t old_space_used(G1CollectedHeap* g1h);
 };
 
 // Memory pool that represents the G1 eden.
@@ -89,10 +70,10 @@
   G1EdenPool(G1CollectedHeap* g1h);
 
   size_t used_in_bytes() {
-    return eden_space_used(_g1h);
+    return _g1mm->eden_space_used();
   }
   size_t max_size() const {
-    return undefined_max();
+    return _undefined_max;
   }
   MemoryUsage get_memory_usage();
 };
@@ -103,10 +84,10 @@
   G1SurvivorPool(G1CollectedHeap* g1h);
 
   size_t used_in_bytes() {
-    return survivor_space_used(_g1h);
+    return _g1mm->survivor_space_used();
   }
   size_t max_size() const {
-    return undefined_max();
+    return _undefined_max;
   }
   MemoryUsage get_memory_usage();
 };
@@ -117,10 +98,10 @@
   G1OldGenPool(G1CollectedHeap* g1h);
 
   size_t used_in_bytes() {
-    return old_space_used(_g1h);
+    return _g1mm->old_space_used();
   }
   size_t max_size() const {
-    return undefined_max();
+    return _undefined_max;
   }
   MemoryUsage get_memory_usage();
 };