1 /*
  2  * Copyright (c) 2000, 2022, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 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_GC_SHARED_GENCOLLECTEDHEAP_HPP
 26 #define SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
 27 
 28 #include "gc/shared/collectedHeap.hpp"
 29 #include "gc/shared/generation.hpp"
 30 #include "gc/shared/oopStorageParState.hpp"
 31 #include "gc/shared/preGCValues.hpp"
 32 #include "gc/shared/softRefGenPolicy.hpp"
 33 
 34 class AdaptiveSizePolicy;
 35 class CardTableRS;
 36 class GCPolicyCounters;
 37 class GenerationSpec;
 38 class StrongRootsScope;
 39 class SubTasksDone;
 40 class WorkerThreads;
 41 
 42 // A "GenCollectedHeap" is a CollectedHeap that uses generational
 43 // collection.  It has two generations, young and old.
 44 class GenCollectedHeap : public CollectedHeap {
 45   friend class Generation;
 46   friend class DefNewGeneration;
 47   friend class TenuredGeneration;
 48   friend class GenMarkSweep;
 49   friend class VM_GenCollectForAllocation;
 50   friend class VM_GenCollectFull;
 51   friend class VM_GC_HeapInspection;
 52   friend class VM_HeapDumper;
 53   friend class HeapInspection;
 54   friend class GCCauseSetter;
 55   friend class VMStructs;
 56 public:
 57   friend class VM_PopulateDumpSharedSpace;
 58 
 59   enum GenerationType {
 60     YoungGen,
 61     OldGen
 62   };
 63 
 64 protected:
 65   Generation* _young_gen;
 66   Generation* _old_gen;
 67 
 68 private:
 69   GenerationSpec* _young_gen_spec;
 70   GenerationSpec* _old_gen_spec;
 71 
 72   // The singleton CardTable Remembered Set.
 73   CardTableRS* _rem_set;
 74 
 75   SoftRefGenPolicy _soft_ref_gen_policy;
 76 
 77   // The sizing of the heap is controlled by a sizing policy.
 78   AdaptiveSizePolicy* _size_policy;
 79 
 80   GCPolicyCounters* _gc_policy_counters;
 81 
 82   // Indicates that the most recent previous incremental collection failed.
 83   // The flag is cleared when an action is taken that might clear the
 84   // condition that caused that incremental collection to fail.
 85   bool _incremental_collection_failed;
 86 
 87   // In support of ExplicitGCInvokesConcurrent functionality
 88   unsigned int _full_collections_completed;
 89 
 90   // Collects the given generation.
 91   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
 92                           bool run_verification, bool clear_soft_refs);
 93 
 94   // Reserve aligned space for the heap as needed by the contained generations.
 95   ReservedHeapSpace allocate(size_t alignment);
 96 
 97   // Initialize ("weak") refs processing support
 98   void ref_processing_init();
 99 
100   PreGenGCValues get_pre_gc_values() const;
101 
102 protected:
103 
104   GCMemoryManager* _young_manager;
105   GCMemoryManager* _old_manager;
106 
107   // Helper functions for allocation
108   HeapWord* attempt_allocation(size_t size,
109                                bool   is_tlab,
110                                bool   first_only);
111 
112   // Helper function for two callbacks below.
113   // Considers collection of the first max_level+1 generations.
114   void do_collection(bool           full,
115                      bool           clear_all_soft_refs,
116                      size_t         size,
117                      bool           is_tlab,
118                      GenerationType max_generation);
119 
120   // Callback from VM_GenCollectForAllocation operation.
121   // This function does everything necessary/possible to satisfy an
122   // allocation request that failed in the youngest generation that should
123   // have handled it (including collection, expansion, etc.)
124   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
125 
126   // Callback from VM_GenCollectFull operation.
127   // Perform a full collection of the first max_level+1 generations.
128   virtual void do_full_collection(bool clear_all_soft_refs);
129   void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
130 
131   // Does the "cause" of GC indicate that
132   // we absolutely __must__ clear soft refs?
133   bool must_clear_all_soft_refs();
134 
135   GenCollectedHeap(Generation::Name young,
136                    Generation::Name old,
137                    const char* policy_counters_name);
138 
139 public:
140 
141   // Returns JNI_OK on success
142   virtual jint initialize();
143   virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
144 
145   void initialize_size_policy(size_t init_eden_size,
146                               size_t init_promo_size,
147                               size_t init_survivor_size);
148 
149   // Does operations required after initialization has been done.
150   void post_initialize();
151 
152   Generation* young_gen() const { return _young_gen; }
153   Generation* old_gen()   const { return _old_gen; }
154 
155   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
156   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
157 
158   MemRegion reserved_region() const { return _reserved; }
159   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
160 
161   GenerationSpec* young_gen_spec() const;
162   GenerationSpec* old_gen_spec() const;
163 
164   virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
165 
166   // Adaptive size policy
167   virtual AdaptiveSizePolicy* size_policy() {
168     return _size_policy;
169   }
170 
171   // Performance Counter support
172   GCPolicyCounters* counters()     { return _gc_policy_counters; }
173 
174   size_t capacity() const;
175   size_t used() const;
176 
177   // Save the "used_region" for both generations.
178   void save_used_regions();
179 
180   size_t max_capacity() const;
181 
182   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
183 
184   // Perform a full collection of the heap; intended for use in implementing
185   // "System.gc". This implies as full a collection as the CollectedHeap
186   // supports. Caller does not hold the Heap_lock on entry.
187   virtual void collect(GCCause::Cause cause);
188 
189   // Perform a full collection of generations up to and including max_generation.
190   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
191   void collect(GCCause::Cause cause, GenerationType max_generation);
192 
193   // Returns "TRUE" iff "p" points into the committed areas of the heap.
194   // The methods is_in() and is_in_youngest() may be expensive to compute
195   // in general, so, to prevent their inadvertent use in product jvm's, we
196   // restrict their use to assertion checking or verification only.
197   bool is_in(const void* p) const;
198 
199   // Returns true if the reference is to an object in the reserved space
200   // for the young generation.
201   // Assumes the young gen address range is less than that of the old gen.
202   bool is_in_young(oop p) const;
203 
204   virtual bool requires_barriers(stackChunkOop obj) const;
205 
206 #ifdef ASSERT
207   bool is_in_partial_collection(const void* p);
208 #endif
209 
210   // Optimized nmethod scanning support routines
211   virtual void register_nmethod(nmethod* nm);
212   virtual void unregister_nmethod(nmethod* nm);
213   virtual void verify_nmethod(nmethod* nm);
214   virtual void flush_nmethod(nmethod* nm);
215 
216   void prune_scavengable_nmethods();
217 
218   // Iteration functions.
219   void oop_iterate(OopIterateClosure* cl);
220   void object_iterate(ObjectClosure* cl);
221   Space* space_containing(const void* addr) const;
222 
223   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
224   // each address in the (reserved) heap is a member of exactly
225   // one block.  The defining characteristic of a block is that it is
226   // possible to find its size, and thus to progress forward to the next
227   // block.  (Blocks may be of different sizes.)  Thus, blocks may
228   // represent Java objects, or they might be free blocks in a
229   // free-list-based heap (or subheap), as long as the two kinds are
230   // distinguishable and the size of each is determinable.
231 
232   // Returns the address of the start of the "block" that contains the
233   // address "addr".  We say "blocks" instead of "object" since some heaps
234   // may not pack objects densely; a chunk may either be an object or a
235   // non-object.
236   HeapWord* block_start(const void* addr) const;
237 
238   // Requires "addr" to be the start of a block, and returns "TRUE" iff
239   // the block is an object. Assumes (and verifies in non-product
240   // builds) that addr is in the allocated part of the heap and is
241   // the start of a chunk.
242   bool block_is_obj(const HeapWord* addr) const;
243 
244   // Section on TLAB's.
245   virtual size_t tlab_capacity(Thread* thr) const;
246   virtual size_t tlab_used(Thread* thr) const;
247   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
248   virtual HeapWord* allocate_new_tlab(size_t min_size,
249                                       size_t requested_size,
250                                       size_t* actual_size);
251 
252   // The "requestor" generation is performing some garbage collection
253   // action for which it would be useful to have scratch space.  The
254   // requestor promises to allocate no more than "max_alloc_words" in any
255   // older generation (via promotion say.)   Any blocks of space that can
256   // be provided are returned as a list of ScratchBlocks, sorted by
257   // decreasing size.
258   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
259   // Allow each generation to reset any scratch space that it has
260   // contributed as it needs.
261   void release_scratch();
262 
263   // Ensure parsability: override
264   virtual void ensure_parsability(bool retire_tlabs);
265 
266   // Total number of full collections completed.
267   unsigned int total_full_collections_completed() {
268     assert(_full_collections_completed <= _total_full_collections,
269            "Can't complete more collections than were started");
270     return _full_collections_completed;
271   }
272 
273   // Update above counter, as appropriate, at the end of a stop-world GC cycle
274   unsigned int update_full_collections_completed();
275 
276   // Update the gc statistics for each generation.
277   void update_gc_stats(Generation* current_generation, bool full) {
278     _old_gen->update_gc_stats(current_generation, full);
279   }
280 
281   bool no_gc_in_progress() { return !is_gc_active(); }
282 
283   // Override.
284   void prepare_for_verify();
285 
286   // Override.
287   void verify(VerifyOption option);
288 
289   // Override.
290   virtual void print_on(outputStream* st) const;
291   virtual void gc_threads_do(ThreadClosure* tc) const;
292   virtual void print_tracing_info() const;
293 
294   // Used to print information about locations in the hs_err file.
295   virtual bool print_location(outputStream* st, void* addr) const;
296 
297   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
298 
299   // The functions below are helper functions that a subclass of
300   // "CollectedHeap" can use in the implementation of its virtual
301   // functions.
302 
303   class GenClosure : public StackObj {
304    public:
305     virtual void do_generation(Generation* gen) = 0;
306   };
307 
308   // Apply "cl.do_generation" to all generations in the heap
309   // If "old_to_young" determines the order.
310   void generation_iterate(GenClosure* cl, bool old_to_young);
311 
312   // Return "true" if all generations have reached the
313   // maximal committed limit that they can reach, without a garbage
314   // collection.
315   virtual bool is_maximal_no_gc() const;
316 
317   // This function returns the CardTableRS object that allows us to scan
318   // generations in a fully generational heap.
319   CardTableRS* rem_set() { return _rem_set; }
320 
321   // Convenience function to be used in situations where the heap type can be
322   // asserted to be this type.
323   static GenCollectedHeap* heap();
324 
325   // The ScanningOption determines which of the roots
326   // the closure is applied to:
327   // "SO_None" does none;
328   enum ScanningOption {
329     SO_None                =  0x0,
330     SO_AllCodeCache        =  0x8,
331     SO_ScavengeCodeCache   = 0x10
332   };
333 
334  protected:
335   void process_roots(ScanningOption so,
336                      OopClosure* strong_roots,
337                      CLDClosure* strong_cld_closure,
338                      CLDClosure* weak_cld_closure,
339                      CodeBlobToOopClosure* code_roots);
340 
341   virtual void gc_prologue(bool full);
342   virtual void gc_epilogue(bool full);
343 
344  public:
345   void full_process_roots(bool is_adjust_phase,
346                           ScanningOption so,
347                           bool only_strong_roots,
348                           OopClosure* root_closure,
349                           CLDClosure* cld_closure);
350 
351   // Apply "root_closure" to all the weak roots of the system.
352   // These include JNI weak roots, string table,
353   // and referents of reachable weak refs.
354   void gen_process_weak_roots(OopClosure* root_closure);
355 
356   // Set the saved marks of generations, if that makes sense.
357   // In particular, if any generation might iterate over the oops
358   // in other generations, it should call this method.
359   void save_marks();
360 
361   // Returns "true" iff no allocations have occurred since the last
362   // call to "save_marks".
363   bool no_allocs_since_save_marks();
364 
365   // Returns true if an incremental collection is likely to fail.
366   // We optionally consult the young gen, if asked to do so;
367   // otherwise we base our answer on whether the previous incremental
368   // collection attempt failed with no corrective action as of yet.
369   bool incremental_collection_will_fail(bool consult_young) {
370     // The first disjunct remembers if an incremental collection failed, even
371     // when we thought (second disjunct) that it would not.
372     return incremental_collection_failed() ||
373            (consult_young && !_young_gen->collection_attempt_is_safe());
374   }
375 
376   // If a generation bails out of an incremental collection,
377   // it sets this flag.
378   bool incremental_collection_failed() const {
379     return _incremental_collection_failed;
380   }
381   void set_incremental_collection_failed() {
382     _incremental_collection_failed = true;
383   }
384   void clear_incremental_collection_failed() {
385     _incremental_collection_failed = false;
386   }
387 
388   // Promotion of obj into gen failed.  Try to promote obj to higher
389   // gens in ascending order; return the new location of obj if successful.
390   // Otherwise, try expand-and-allocate for obj in both the young and old
391   // generation; return the new location of obj if successful.  Otherwise, return NULL.
392   oop handle_failed_promotion(Generation* old_gen,
393                               oop obj,
394                               size_t obj_size);
395 
396 
397 private:
398   // Return true if an allocation should be attempted in the older generation
399   // if it fails in the younger generation.  Return false, otherwise.
400   bool should_try_older_generation_allocation(size_t word_size) const;
401 
402   // Try to allocate space by expanding the heap.
403   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
404 
405   HeapWord* mem_allocate_work(size_t size,
406                               bool is_tlab,
407                               bool* gc_overhead_limit_was_exceeded);
408 
409 #if INCLUDE_SERIALGC
410   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
411   // in an essential way: compaction is performed across generations, by
412   // iterating over spaces.
413   void prepare_for_compaction();
414 #endif
415 
416   // Save the tops of the spaces in all generations
417   void record_gen_tops_before_GC() PRODUCT_RETURN;
418 
419   // Return true if we need to perform full collection.
420   bool should_do_full_collection(size_t size, bool full,
421                                  bool is_tlab, GenerationType max_gen) const;
422 };
423 
424 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP