1 /*
   2  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "gc/shared/collectedHeap.hpp"
  25 #include "gc/epsilon/epsilonCollectorPolicy.hpp"
  26 #include "gc/epsilon/epsilonBarrierSet.hpp"
  27 
  28 class EpsilonCollectedHeap : public CollectedHeap {
  29 private:
  30   EpsilonCollectorPolicy* _policy;
  31   HeapWord* _start;
  32   HeapWord* _end;
  33   volatile HeapWord* _current;
  34 public:
  35   EpsilonCollectedHeap(EpsilonCollectorPolicy* p) : _policy(p) {};
  36 
  37   virtual Name kind() const {
  38     return CollectedHeap::EpsilonCollectedHeap;
  39   }
  40 
  41   virtual const char *name() const {
  42     return "Epsilon GC";
  43   }
  44 
  45   virtual jint initialize();
  46 
  47   virtual void post_initialize() {}
  48 
  49   virtual size_t capacity()     const { return pointer_delta(_end, _start); }
  50   virtual size_t used()         const { return pointer_delta((HeapWord*)_current, _start); }
  51   virtual size_t max_capacity() const { return capacity(); }
  52 
  53   virtual bool is_maximal_no_gc() const { return used() == capacity(); } // TODO: Really?
  54 
  55   virtual bool is_in(const void *p) const { return (_start <= p) && (p < _end); }
  56 
  57   virtual bool is_scavengable(const void *p) { return true; } // TODO: Why?
  58 
  59   virtual HeapWord* mem_allocate(size_t size, bool *gc_overhead_limit_was_exceeded);
  60   virtual HeapWord* allocate_new_tlab(size_t size);
  61 
  62   virtual HeapWord* allocate_work(size_t size);
  63 
  64   // TLAB allocations
  65   virtual bool supports_tlab_allocation()           const { return true; }
  66   virtual size_t tlab_capacity(Thread *thr)         const { return capacity(); }
  67   virtual size_t tlab_used(Thread *thr)             const { return used(); } // TODO: Should probably record the TLAB?
  68   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
  69     // TODO: hook up in TLAB policy better. pointer_delta(_current, _end);
  70     return HeapWordSize * 128 * K;
  71   }
  72 
  73   virtual bool can_elide_tlab_store_barriers() const {
  74     return true; // TODO: Really?
  75   }
  76 
  77   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
  78     return true; // TODO: Really?
  79   }
  80 
  81   virtual bool card_mark_must_follow_store() const {
  82     return true; // TODO: Really?
  83   }
  84 
  85   virtual void collect(GCCause::Cause cause);
  86   virtual void do_full_collection(bool clear_all_soft_refs);
  87 
  88   virtual AdaptiveSizePolicy *size_policy() {
  89     // No such thing for Epsilon
  90     return NULL;
  91   }
  92 
  93   virtual CollectorPolicy *collector_policy() const {
  94     return _policy;
  95   }
  96 
  97   virtual void object_iterate(ObjectClosure *cl) {
  98     safe_object_iterate(cl);
  99   }
 100 
 101   virtual void safe_object_iterate(ObjectClosure *cl);
 102 
 103   virtual HeapWord *block_start(const void *addr) const {
 104     Unimplemented();
 105     return NULL;
 106   }
 107 
 108   virtual size_t block_size(const HeapWord *addr) const {
 109     Unimplemented();
 110     return 0;
 111   }
 112 
 113   virtual bool block_is_obj(const HeapWord *addr) const {
 114     Unimplemented();
 115     return false;
 116   }
 117 
 118   virtual jlong millis_since_last_gc() {
 119     return os::elapsed_counter() / NANOSECS_PER_MILLISEC; // since the VM start
 120   }
 121 
 122   virtual void prepare_for_verify() {
 123     // No heap verification.
 124   }
 125 
 126   virtual void print_on(outputStream *st) const {
 127     // Print nothing.
 128   }
 129 
 130   virtual void print_gc_threads_on(outputStream *st) const {
 131     // No GC threads.
 132   }
 133 
 134   virtual void gc_threads_do(ThreadClosure *tc) const {
 135     // No GC threads.
 136   }
 137 
 138   virtual void print_tracing_info() const {
 139     Log(gc) log;
 140     size_t allocated_kb = pointer_delta((HeapWord*)_current, _start) * HeapWordSize / K;
 141     log.info("Total allocated: " SIZE_FORMAT " KB.",
 142              allocated_kb);
 143     log.info("Average allocation rate: " SIZE_FORMAT " KB/sec",
 144              allocated_kb * NANOSECS_PER_SEC / os::elapsed_counter());
 145   }
 146 
 147   virtual void verify(VerifyOption option) {
 148     // No heap verification for Epsilon.
 149   }
 150 
 151 };