15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_MEMORY_SHAREDHEAP_HPP 26 #define SHARE_VM_MEMORY_SHAREDHEAP_HPP 27 28 #include "gc_interface/collectedHeap.hpp" 29 30 // A "SharedHeap" is an implementation of a java heap for HotSpot. This 31 // is an abstract class: there may be many different kinds of heaps. This 32 // class defines the functions that a heap must implement, and contains 33 // infrastructure common to all heaps. 34 35 class FlexibleWorkGang; 36 37 // Note on use of FlexibleWorkGang's for GC. 38 // There are three places where task completion is determined. 39 // In 40 // 1) ParallelTaskTerminator::offer_termination() where _n_threads 41 // must be set to the correct value so that count of workers that 42 // have offered termination will exactly match the number 43 // working on the task. Tasks such as those derived from GCTask 44 // use ParallelTaskTerminator's. Tasks that want load balancing 45 // by work stealing use this method to gauge completion. 46 // 2) SubTasksDone has a variable _n_threads that is used in 47 // all_tasks_completed() to determine completion. all_tasks_complete() 48 // counts the number of tasks that have been done and then reset 49 // the SubTasksDone so that it can be used again. When the number of 50 // tasks is set to the number of GC workers, then _n_threads must 51 // be set to the number of active GC workers. G1RootProcessor and 52 // GenCollectedHeap have SubTasksDone. 53 // 3) SequentialSubTasksDone has an _n_threads that is used in 54 // a way similar to SubTasksDone and has the same dependency on the 55 // number of active GC workers. CompactibleFreeListSpace and Space 56 // have SequentialSubTasksDone's. 72 // The pattern that appears in the code is to set _n_threads 73 // to a value > 1 before a task that you would like executed in parallel 74 // and then to set it to 0 after that task has completed. A value of 75 // 0 is a "special" value in set_n_threads() which translates to 76 // setting _n_threads to 1. 77 // 78 // Some code uses _n_termination to decide if work should be done in 79 // parallel. The notorious possibly_parallel_oops_do() in threads.cpp 80 // is an example of such code. Look for variable "is_par" for other 81 // examples. 82 // 83 // The active_workers is not reset to 0 after a parallel phase. It's 84 // value may be used in later phases and in one instance at least 85 // (the parallel remark) it has to be used (the parallel remark depends 86 // on the partitioning done in the previous parallel scavenge). 87 88 class SharedHeap : public CollectedHeap { 89 friend class VMStructs; 90 91 protected: 92 // If we're doing parallel GC, use this gang of threads. 93 FlexibleWorkGang* _workers; 94 95 // Full initialization is done in a concrete subtype's "initialize" 96 // function. 97 SharedHeap(); 98 99 public: 100 // Note, the below comment needs to be updated to reflect the changes 101 // introduced by JDK-8076225. This should be done as part of JDK-8076289. 102 // 103 //Some collectors will perform "process_strong_roots" in parallel. 104 // Such a call will involve claiming some fine-grained tasks, such as 105 // scanning of threads. To make this process simpler, we provide the 106 // "strong_roots_parity()" method. Collectors that start parallel tasks 107 // whose threads invoke "process_strong_roots" must 108 // call "change_strong_roots_parity" in sequential code starting such a 109 // task. (This also means that a parallel thread may only call 110 // process_strong_roots once.) 111 // 112 // For calls to process_roots by sequential code, the parity is 113 // updated automatically. 114 // 120 // 121 // If the client meats this spec, then strong_roots_parity() will have 122 // the following properties: 123 // a) to return a different value than was returned before the last 124 // call to change_strong_roots_parity, and 125 // c) to never return a distinguished value (zero) with which such 126 // task-claiming variables may be initialized, to indicate "never 127 // claimed". 128 public: 129 130 // Call these in sequential code around process_roots. 131 // strong_roots_prologue calls change_strong_roots_parity, if 132 // parallel tasks are enabled. 133 class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope { 134 SharedHeap* _sh; 135 136 public: 137 StrongRootsScope(SharedHeap* heap, bool activate = true); 138 ~StrongRootsScope(); 139 }; 140 141 private: 142 143 public: 144 FlexibleWorkGang* workers() const { return _workers; } 145 146 // The functions below are helper functions that a subclass of 147 // "SharedHeap" can use in the implementation of its virtual 148 // functions. 149 }; 150 151 #endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP | 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_MEMORY_SHAREDHEAP_HPP 26 #define SHARE_VM_MEMORY_SHAREDHEAP_HPP 27 28 #include "gc_interface/collectedHeap.hpp" 29 30 // A "SharedHeap" is an implementation of a java heap for HotSpot. This 31 // is an abstract class: there may be many different kinds of heaps. This 32 // class defines the functions that a heap must implement, and contains 33 // infrastructure common to all heaps. 34 35 // Note on use of FlexibleWorkGang's for GC. 36 // There are three places where task completion is determined. 37 // In 38 // 1) ParallelTaskTerminator::offer_termination() where _n_threads 39 // must be set to the correct value so that count of workers that 40 // have offered termination will exactly match the number 41 // working on the task. Tasks such as those derived from GCTask 42 // use ParallelTaskTerminator's. Tasks that want load balancing 43 // by work stealing use this method to gauge completion. 44 // 2) SubTasksDone has a variable _n_threads that is used in 45 // all_tasks_completed() to determine completion. all_tasks_complete() 46 // counts the number of tasks that have been done and then reset 47 // the SubTasksDone so that it can be used again. When the number of 48 // tasks is set to the number of GC workers, then _n_threads must 49 // be set to the number of active GC workers. G1RootProcessor and 50 // GenCollectedHeap have SubTasksDone. 51 // 3) SequentialSubTasksDone has an _n_threads that is used in 52 // a way similar to SubTasksDone and has the same dependency on the 53 // number of active GC workers. CompactibleFreeListSpace and Space 54 // have SequentialSubTasksDone's. 70 // The pattern that appears in the code is to set _n_threads 71 // to a value > 1 before a task that you would like executed in parallel 72 // and then to set it to 0 after that task has completed. A value of 73 // 0 is a "special" value in set_n_threads() which translates to 74 // setting _n_threads to 1. 75 // 76 // Some code uses _n_termination to decide if work should be done in 77 // parallel. The notorious possibly_parallel_oops_do() in threads.cpp 78 // is an example of such code. Look for variable "is_par" for other 79 // examples. 80 // 81 // The active_workers is not reset to 0 after a parallel phase. It's 82 // value may be used in later phases and in one instance at least 83 // (the parallel remark) it has to be used (the parallel remark depends 84 // on the partitioning done in the previous parallel scavenge). 85 86 class SharedHeap : public CollectedHeap { 87 friend class VMStructs; 88 89 protected: 90 // Full initialization is done in a concrete subtype's "initialize" 91 // function. 92 SharedHeap(); 93 94 public: 95 // Note, the below comment needs to be updated to reflect the changes 96 // introduced by JDK-8076225. This should be done as part of JDK-8076289. 97 // 98 //Some collectors will perform "process_strong_roots" in parallel. 99 // Such a call will involve claiming some fine-grained tasks, such as 100 // scanning of threads. To make this process simpler, we provide the 101 // "strong_roots_parity()" method. Collectors that start parallel tasks 102 // whose threads invoke "process_strong_roots" must 103 // call "change_strong_roots_parity" in sequential code starting such a 104 // task. (This also means that a parallel thread may only call 105 // process_strong_roots once.) 106 // 107 // For calls to process_roots by sequential code, the parity is 108 // updated automatically. 109 // 115 // 116 // If the client meats this spec, then strong_roots_parity() will have 117 // the following properties: 118 // a) to return a different value than was returned before the last 119 // call to change_strong_roots_parity, and 120 // c) to never return a distinguished value (zero) with which such 121 // task-claiming variables may be initialized, to indicate "never 122 // claimed". 123 public: 124 125 // Call these in sequential code around process_roots. 126 // strong_roots_prologue calls change_strong_roots_parity, if 127 // parallel tasks are enabled. 128 class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope { 129 SharedHeap* _sh; 130 131 public: 132 StrongRootsScope(SharedHeap* heap, bool activate = true); 133 ~StrongRootsScope(); 134 }; 135 }; 136 137 #endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP |