jmasa@2821: /*
jmasa@2821:  * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
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jmasa@2821:  * published by the Free Software Foundation.
jmasa@2821:  *
jmasa@2821:  * This code is distributed in the hope that it will be useful, but WITHOUT
jmasa@2821:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jmasa@2821:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jmasa@2821:  * version 2 for more details (a copy is included in the LICENSE file that
jmasa@2821:  * accompanied this code).
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jmasa@2821: 
jmasa@2821: #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP
jmasa@2821: #define SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP
jmasa@2821: 
jmasa@2821: #include "gc_implementation/shared/hSpaceCounters.hpp"
jmasa@2821: 
jmasa@2821: class G1CollectedHeap;
jmasa@2821: class G1SpaceMonitoringSupport;
jmasa@2821: 
jmasa@2821: // Class for monitoring logical spaces in G1.
jmasa@2821: // G1 defines a set of regions as a young
jmasa@2821: // collection (analogous to a young generation).
jmasa@2821: // The young collection is a logical generation
jmasa@2821: // with no fixed chunk (see space.hpp) reflecting
jmasa@2821: // the address space for the generation.  In addition
jmasa@2821: // to the young collection there is its complement
jmasa@2821: // the non-young collection that is simply the regions
jmasa@2821: // not in the young collection.  The non-young collection
jmasa@2821: // is treated here as a logical old generation only
jmasa@2821: // because the monitoring tools expect a generational
jmasa@2821: // heap.  The monitoring tools expect that a Space
jmasa@2821: // (see space.hpp) exists that describe the
jmasa@2821: // address space of young collection and non-young
jmasa@2821: // collection and such a view is provided here.
jmasa@2821: //
jmasa@2821: // This class provides interfaces to access
jmasa@2821: // the value of variables for the young collection
jmasa@2821: // that include the "capacity" and "used" of the
jmasa@2821: // young collection along with constant values
jmasa@2821: // for the minimum and maximum capacities for
jmasa@2821: // the logical spaces.  Similarly for the non-young
jmasa@2821: // collection.
jmasa@2821: //
jmasa@2821: // Also provided are counters for G1 concurrent collections
jmasa@2821: // and stop-the-world full heap collecitons.
jmasa@2821: //
jmasa@2821: // Below is a description of how "used" and "capactiy"
jmasa@2821: // (or committed) is calculated for the logical spaces.
jmasa@2821: //
jmasa@2821: // 1) The used space calculation for a pool is not necessarily
jmasa@2821: // independent of the others. We can easily get from G1 the overall
jmasa@2821: // used space in the entire heap, the number of regions in the young
jmasa@2821: // generation (includes both eden and survivors), and the number of
jmasa@2821: // survivor regions. So, from that we calculate:
jmasa@2821: //
jmasa@2821: //  survivor_used = survivor_num * region_size
jmasa@2821: //  eden_used     = young_region_num * region_size - survivor_used
jmasa@2821: //  old_gen_used  = overall_used - eden_used - survivor_used
jmasa@2821: //
jmasa@2821: // Note that survivor_used and eden_used are upper bounds. To get the
jmasa@2821: // actual value we would have to iterate over the regions and add up
jmasa@2821: // ->used(). But that'd be expensive. So, we'll accept some lack of
jmasa@2821: // accuracy for those two. But, we have to be careful when calculating
jmasa@2821: // old_gen_used, in case we subtract from overall_used more then the
jmasa@2821: // actual number and our result goes negative.
jmasa@2821: //
jmasa@2821: // 2) Calculating the used space is straightforward, as described
jmasa@2821: // above. However, how do we calculate the committed space, given that
jmasa@2821: // we allocate space for the eden, survivor, and old gen out of the
jmasa@2821: // same pool of regions? One way to do this is to use the used value
jmasa@2821: // as also the committed value for the eden and survivor spaces and
jmasa@2821: // then calculate the old gen committed space as follows:
jmasa@2821: //
jmasa@2821: //  old_gen_committed = overall_committed - eden_committed - survivor_committed
jmasa@2821: //
jmasa@2821: // Maybe a better way to do that would be to calculate used for eden
jmasa@2821: // and survivor as a sum of ->used() over their regions and then
jmasa@2821: // calculate committed as region_num * region_size (i.e., what we use
jmasa@2821: // to calculate the used space now). This is something to consider
jmasa@2821: // in the future.
jmasa@2821: //
jmasa@2821: // 3) Another decision that is again not straightforward is what is
jmasa@2821: // the max size that each memory pool can grow to. One way to do this
jmasa@2821: // would be to use the committed size for the max for the eden and
jmasa@2821: // survivors and calculate the old gen max as follows (basically, it's
jmasa@2821: // a similar pattern to what we use for the committed space, as
jmasa@2821: // described above):
jmasa@2821: //
jmasa@2821: //  old_gen_max = overall_max - eden_max - survivor_max
jmasa@2821: //
jmasa@2821: // Unfortunately, the above makes the max of each pool fluctuate over
jmasa@2821: // time and, even though this is allowed according to the spec, it
jmasa@2821: // broke several assumptions in the M&M framework (there were cases
jmasa@2821: // where used would reach a value greater than max). So, for max we
jmasa@2821: // use -1, which means "undefined" according to the spec.
jmasa@2821: //
jmasa@2821: // 4) Now, there is a very subtle issue with all the above. The
jmasa@2821: // framework will call get_memory_usage() on the three pools
jmasa@2821: // asynchronously. As a result, each call might get a different value
jmasa@2821: // for, say, survivor_num which will yield inconsistent values for
jmasa@2821: // eden_used, survivor_used, and old_gen_used (as survivor_num is used
jmasa@2821: // in the calculation of all three). This would normally be
jmasa@2821: // ok. However, it's possible that this might cause the sum of
jmasa@2821: // eden_used, survivor_used, and old_gen_used to go over the max heap
jmasa@2821: // size and this seems to sometimes cause JConsole (and maybe other
jmasa@2821: // clients) to get confused. There's not a really an easy / clean
jmasa@2821: // solution to this problem, due to the asynchrounous nature of the
jmasa@2821: // framework.
jmasa@2821: 
jmasa@2821: class G1MonitoringSupport : public CHeapObj {
jmasa@2821:   G1CollectedHeap* _g1h;
jmasa@2821:   VirtualSpace* _g1_storage_addr;
jmasa@2821: 
jmasa@2821:   // jstat performance counters
jmasa@2821:   //  incremental collections both fully and partially young
jmasa@2821:   CollectorCounters*   _incremental_collection_counters;
jmasa@2821:   //  full stop-the-world collections
jmasa@2821:   CollectorCounters*   _full_collection_counters;
jmasa@2821:   //  young collection set counters.  The _eden_counters,
jmasa@2821:   // _from_counters, and _to_counters are associated with
jmasa@2821:   // this "generational" counter.
jmasa@2821:   GenerationCounters*  _young_collection_counters;
jmasa@2821:   //  non-young collection set counters. The _old_space_counters
jmasa@2821:   // below are associated with this "generational" counter.
jmasa@2821:   GenerationCounters*  _non_young_collection_counters;
jmasa@2821:   // Counters for the capacity and used for
jmasa@2821:   //   the whole heap
jmasa@2821:   HSpaceCounters*      _old_space_counters;
jmasa@2821:   //   the young collection
jmasa@2821:   HSpaceCounters*      _eden_counters;
jmasa@2821:   //   the survivor collection (only one, _to_counters, is actively used)
jmasa@2821:   HSpaceCounters*      _from_counters;
jmasa@2821:   HSpaceCounters*      _to_counters;
jmasa@2821: 
jmasa@2821:   // It returns x - y if x > y, 0 otherwise.
jmasa@2821:   // As described in the comment above, some of the inputs to the
jmasa@2821:   // calculations we have to do are obtained concurrently and hence
jmasa@2821:   // may be inconsistent with each other. So, this provides a
jmasa@2821:   // defensive way of performing the subtraction and avoids the value
jmasa@2821:   // going negative (which would mean a very large result, given that
jmasa@2821:   // the parameter are size_t).
jmasa@2821:   static size_t subtract_up_to_zero(size_t x, size_t y) {
jmasa@2821:     if (x > y) {
jmasa@2821:       return x - y;
jmasa@2821:     } else {
jmasa@2821:       return 0;
jmasa@2821:     }
jmasa@2821:   }
jmasa@2821: 
jmasa@2821:  public:
jmasa@2821:   G1MonitoringSupport(G1CollectedHeap* g1h, VirtualSpace* g1_storage_addr);
jmasa@2821: 
jmasa@2821:   G1CollectedHeap* g1h() { return _g1h; }
jmasa@2821:   VirtualSpace* g1_storage_addr() { return _g1_storage_addr; }
jmasa@2821: 
jmasa@2821:   // Performance Counter accessors
jmasa@2821:   void update_counters();
jmasa@2821:   void update_eden_counters();
jmasa@2821: 
jmasa@2821:   CollectorCounters* incremental_collection_counters() {
jmasa@2821:     return _incremental_collection_counters;
jmasa@2821:   }
jmasa@2821:   CollectorCounters* full_collection_counters() {
jmasa@2821:     return _full_collection_counters;
jmasa@2821:   }
jmasa@2821:   GenerationCounters* non_young_collection_counters() {
jmasa@2821:     return _non_young_collection_counters;
jmasa@2821:   }
jmasa@2821:   HSpaceCounters*      old_space_counters() { return _old_space_counters; }
jmasa@2821:   HSpaceCounters*      eden_counters() { return _eden_counters; }
jmasa@2821:   HSpaceCounters*      from_counters() { return _from_counters; }
jmasa@2821:   HSpaceCounters*      to_counters() { return _to_counters; }
jmasa@2821: 
jmasa@2821:   // Monitoring support used by
jmasa@2821:   //   MemoryService
jmasa@2821:   //   jstat counters
jmasa@2821:   size_t overall_committed();
jmasa@2821:   size_t overall_used();
jmasa@2821: 
jmasa@2821:   size_t eden_space_committed();
jmasa@2821:   size_t eden_space_used();
jmasa@2821: 
jmasa@2821:   size_t survivor_space_committed();
jmasa@2821:   size_t survivor_space_used();
jmasa@2821: 
jmasa@2821:   size_t old_space_committed();
jmasa@2821:   size_t old_space_used();
jmasa@2821: };
jmasa@2821: 
jmasa@2821: #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP