--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1MonitoringSupport.hpp Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,269 @@
+/*
+ * Copyright (c) 2011, 2015, 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_G1_G1MONITORINGSUPPORT_HPP
+#define SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP
+
+#include "gc/g1/hSpaceCounters.hpp"
+
+class G1CollectedHeap;
+
+// Class for monitoring logical spaces in G1. It provides data for
+// both G1's jstat counters as well as G1's memory pools.
+//
+// G1 splits the heap into heap regions and each heap region belongs
+// to one of the following categories:
+//
+// * 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
+//
+// 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.
+//
+// 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.
+//
+// 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.
+//
+// Below is a description of how the various sizes are calculated.
+//
+// * Current Capacity
+//
+// - 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
+//
+// What we do in the above is to distribute the free regions among
+// eden_capacity and old_capacity.
+//
+// * Occupancy
+//
+// - 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, 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.
+//
+// * Min Capacity
+//
+// We set this to 0 for all spaces.
+//
+// * Max Capacity
+//
+// For jstat, we set the max capacity of all spaces to heap_capacity,
+// given that we don't always have a reasonable upper bound on how big
+// each space can grow. For the memory pools, we make the max
+// capacity undefined with the exception of the old memory pool for
+// which we make the max capacity same as the max heap capacity.
+//
+// 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 recalculation to
+// do which is important as we want to keep the eden region allocation
+// path as low-overhead as possible.
+
+class G1MonitoringSupport : public CHeapObj<mtGC> {
+ friend class VMStructs;
+
+ G1CollectedHeap* _g1h;
+
+ // jstat performance counters
+ // incremental collections both young and mixed
+ 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;
+ // old collection set counters. The _old_space_counters
+ // below are associated with this "generational" counter.
+ GenerationCounters* _old_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;
+
+ // 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;
+
+ uint _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
+ // 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;
+ }
+ }
+
+ // 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);
+
+ // 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;
+ }
+
+ // 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;
+ }
+ CollectorCounters* full_collection_counters() {
+ return _full_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; }
+ HSpaceCounters* from_counters() { return _from_counters; }
+ HSpaceCounters* to_counters() { return _to_counters; }
+
+ // Monitoring support used by
+ // MemoryService
+ // jstat counters
+ // Tracing
+
+ size_t overall_reserved() { return _overall_reserved; }
+ size_t overall_committed() { return _overall_committed; }
+ size_t overall_used() { return _overall_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_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_G1_G1MONITORINGSUPPORT_HPP