jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp@4f93f0d00802 (annotated)

src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp@4f93f0d00802 (annotated)

src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp

Tue, 20 Sep 2011 09:59:59 -0400

author: tonyp
date: Tue, 20 Sep 2011 09:59:59 -0400
changeset 3168: 4f93f0d00802
parent 2821: b52782ae3880
child 3176: 8229bd737950
permissions: -rw-r--r--

7059019: G1: add G1 support to the SA
Summary: Extend the SA to recognize the G1CollectedHeap and implement any code that's needed by our serviceability tools (jmap, jinfo, jstack, etc.) that depend on the SA.
Reviewed-by: never, poonam, johnc

 /*
  * 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_G1MONITORINGSUPPORT_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP
 #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.
 //
 // 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.
 //
 // Also provided are counters for G1 concurrent collections
 // and stop-the-world full heap collecitons.
 //
 // Below is a description of how "used" and "capactiy"
 // (or committed) is calculated for the logical spaces.
 //
 // 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:
 //
 //  survivor_used = survivor_num * region_size
 //  eden_used     = young_region_num * region_size - survivor_used
 //  old_gen_used  = overall_used - eden_used - survivor_used
 //
 // 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.
 //
 // 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:
 //
 //  old_gen_committed = overall_committed - eden_committed - survivor_committed
 //
 // 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.
 //
 // 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):
 //
 //  old_gen_max = overall_max - eden_max - survivor_max
 //
 // 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.
 //
 // 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.
 class G1MonitoringSupport : public CHeapObj {
   G1CollectedHeap* _g1h;
   VirtualSpace* _g1_storage_addr;
   // jstat performance counters
   //  incremental collections both fully and partially young
   CollectorCounters*   _incremental_collection_counters;
   //  full stop-the-world collections
   CollectorCounters*   _full_collection_counters;
   //  young collection set counters.  The _eden_counters,
   // _from_counters, and _to_counters are associated with
   // this "generational" counter.
   GenerationCounters*  _young_collection_counters;
   //  non-young collection set counters. The _old_space_counters
   // below are associated with this "generational" counter.
   GenerationCounters*  _non_young_collection_counters;
   // Counters for the capacity and used for
   //   the whole heap
   HSpaceCounters*      _old_space_counters;
   //   the young collection
   HSpaceCounters*      _eden_counters;
   //   the survivor collection (only one, _to_counters, is actively used)
   HSpaceCounters*      _from_counters;
   HSpaceCounters*      _to_counters;
   // 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
   // may be inconsistent with each other. So, this provides a
   // defensive way of performing the subtraction and avoids the value
   // going negative (which would mean a very large result, given that
   // the parameter are size_t).
   static size_t subtract_up_to_zero(size_t x, size_t y) {
     if (x > y) {
       return x - y;
     } else {
       return 0;
     }
   }
  public:
   G1MonitoringSupport(G1CollectedHeap* g1h, VirtualSpace* g1_storage_addr);
   G1CollectedHeap* g1h() { return _g1h; }
   VirtualSpace* g1_storage_addr() { return _g1_storage_addr; }
   // Performance Counter accessors
   void update_counters();
   void update_eden_counters();
   CollectorCounters* incremental_collection_counters() {
     return _incremental_collection_counters;
   }
   CollectorCounters* full_collection_counters() {
     return _full_collection_counters;
   }
   GenerationCounters* non_young_collection_counters() {
     return _non_young_collection_counters;
   }
   HSpaceCounters*      old_space_counters() { return _old_space_counters; }
   HSpaceCounters*      eden_counters() { return _eden_counters; }
   HSpaceCounters*      from_counters() { return _from_counters; }
   HSpaceCounters*      to_counters() { return _to_counters; }
   // 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 survivor_space_committed();
   size_t survivor_space_used();
   size_t old_space_committed();
   size_t old_space_used();
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1MONITORINGSUPPORT_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp@4f93f0d00802 (annotated)

src/share/vm/gc_implementation/g1/g1MonitoringSupport.hpp