diff -r e45861098f5a -r fec48bf5a827 hotspot/src/share/vm/gc/g1/g1MonitoringSupport.hpp --- /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 { + 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