vm/gc.cpp

   1 #include "master.hpp"
   2
   3 namespace factor
   4 {
   5
   6 gc_event::gc_event(gc_op op_, factor_vm *parent) :
   7         op(op_),
   8         cards_scanned(0),
   9         decks_scanned(0),
  10         code_blocks_scanned(0),
  11         start_time(nano_count()),
  12         card_scan_time(0),
  13         code_scan_time(0),
  14         data_sweep_time(0),
  15         code_sweep_time(0),
  16         compaction_time(0)
  17 {
  18         data_heap_before = parent->data_room();
  19         code_heap_before = parent->code_room();
  20         start_time = nano_count();
  21 }
  22
  23 void gc_event::started_card_scan()
  24 {
  25         temp_time = nano_count();
  26 }
  27
  28 void gc_event::ended_card_scan(cell cards_scanned_, cell decks_scanned_)
  29 {
  30         cards_scanned += cards_scanned_;
  31         decks_scanned += decks_scanned_;
  32         card_scan_time = (cell)(nano_count() - temp_time);
  33 }
  34
  35 void gc_event::started_code_scan()
  36 {
  37         temp_time = nano_count();
  38 }
  39
  40 void gc_event::ended_code_scan(cell code_blocks_scanned_)
  41 {
  42         code_blocks_scanned += code_blocks_scanned_;
  43         code_scan_time = (cell)(nano_count() - temp_time);
  44 }
  45
  46 void gc_event::started_data_sweep()
  47 {
  48         temp_time = nano_count();
  49 }
  50
  51 void gc_event::ended_data_sweep()
  52 {
  53         data_sweep_time = (cell)(nano_count() - temp_time);
  54 }
  55
  56 void gc_event::started_code_sweep()
  57 {
  58         temp_time = nano_count();
  59 }
  60
  61 void gc_event::ended_code_sweep()
  62 {
  63         code_sweep_time = (cell)(nano_count() - temp_time);
  64 }
  65
  66 void gc_event::started_compaction()
  67 {
  68         temp_time = nano_count();
  69 }
  70
  71 void gc_event::ended_compaction()
  72 {
  73         compaction_time = (cell)(nano_count() - temp_time);
  74 }
  75
  76 void gc_event::ended_gc(factor_vm *parent)
  77 {
  78         data_heap_after = parent->data_room();
  79         code_heap_after = parent->code_room();
  80         total_time = (cell)(nano_count() - start_time);
  81 }
  82
  83 gc_state::gc_state(gc_op op_, factor_vm *parent) : op(op_)
  84 {
  85         if(parent->gc_events)
  86         {
  87                 event = new gc_event(op,parent);
  88                 start_time = nano_count();
  89         }
  90         else
  91                 event = NULL;
  92 }
  93
  94 gc_state::~gc_state()
  95 {
  96         if(event)
  97         {
  98                 delete event;
  99                 event = NULL;
 100         }
 101 }
 102
 103 void factor_vm::end_gc()
 104 {
 105         if(gc_events)
 106         {
 107                 current_gc->event->ended_gc(this);
 108                 gc_events->push_back(*current_gc->event);
 109         }
 110 }
 111
 112 void factor_vm::start_gc_again()
 113 {
 114         end_gc();
 115
 116         switch(current_gc->op)
 117         {
 118         case collect_nursery_op:
 119                 /* Nursery collection can fail if aging does not have enough
 120                 free space to fit all live objects from nursery. */
 121                 current_gc->op = collect_aging_op;
 122                 break;
 123         case collect_aging_op:
 124                 /* Aging collection can fail if the aging semispace cannot fit
 125                 all the live objects from the other aging semispace and the
 126                 nursery. */
 127                 current_gc->op = collect_to_tenured_op;
 128                 break;
 129         default:
 130                 /* Nothing else should fail mid-collection due to insufficient
 131                 space in the target generation. */
 132                 critical_error("Bad GC op",current_gc->op);
 133                 break;
 134         }
 135
 136         if(gc_events)
 137                 current_gc->event = new gc_event(current_gc->op,this);
 138 }
 139
 140 void factor_vm::set_current_gc_op(gc_op op)
 141 {
 142         current_gc->op = op;
 143         if(gc_events) current_gc->event->op = op;
 144 }
 145
 146 void factor_vm::gc(gc_op op, cell requested_size, bool trace_contexts_p)
 147 {
 148         FACTOR_ASSERT(!gc_off);
 149         FACTOR_ASSERT(!current_gc);
 150
 151         /* Important invariant: tenured space must have enough contiguous free
 152         space to fit the entire contents of the aging space and nursery. This is
 153         because when doing a full collection, objects from younger generations
 154         are promoted before any unreachable tenured objects are freed. */
 155         FACTOR_ASSERT(!data->high_fragmentation_p());
 156
 157         current_gc = new gc_state(op,this);
 158         atomic::store(&current_gc_p, true);
 159
 160         /* Keep trying to GC higher and higher generations until we don't run
 161         out of space in the target generation. */
 162         for(;;)
 163         {
 164                 try
 165                 {
 166                         if(gc_events) current_gc->event->op = current_gc->op;
 167
 168                         switch(current_gc->op)
 169                         {
 170                         case collect_nursery_op:
 171                                 collect_nursery();
 172                                 break;
 173                         case collect_aging_op:
 174                                 /* We end up here if the above fails. */
 175                                 collect_aging();
 176                                 if(data->high_fragmentation_p())
 177                                 {
 178                                         /* Change GC op so that if we fail again,
 179                                         we crash. */
 180                                         set_current_gc_op(collect_full_op);
 181                                         collect_full(trace_contexts_p);
 182                                 }
 183                                 break;
 184                         case collect_to_tenured_op:
 185                                 /* We end up here if the above fails. */
 186                                 collect_to_tenured();
 187                                 if(data->high_fragmentation_p())
 188                                 {
 189                                         /* Change GC op so that if we fail again,
 190                                         we crash. */
 191                                         set_current_gc_op(collect_full_op);
 192                                         collect_full(trace_contexts_p);
 193                                 }
 194                                 break;
 195                         case collect_full_op:
 196                                 collect_full(trace_contexts_p);
 197                                 break;
 198                         case collect_compact_op:
 199                                 collect_compact(trace_contexts_p);
 200                                 break;
 201                         case collect_growing_heap_op:
 202                                 collect_growing_heap(requested_size,trace_contexts_p);
 203                                 break;
 204                         default:
 205                                 critical_error("Bad GC op",current_gc->op);
 206                                 break;
 207                         }
 208
 209                         break;
 210                 }
 211                 catch(const must_start_gc_again &)
 212                 {
 213                         /* We come back here if the target generation is full. */
 214                         start_gc_again();
 215                         continue;
 216                 }
 217         }
 218
 219         end_gc();
 220
 221         atomic::store(&current_gc_p, false);
 222         delete current_gc;
 223         current_gc = NULL;
 224
 225         /* Check the invariant again, just in case. */
 226         FACTOR_ASSERT(!data->high_fragmentation_p());
 227 }
 228
 229 /* primitive_minor_gc() is invoked by inline GC checks, and it needs to fill in
 230 uninitialized stack locations before actually calling the GC. See the comment
 231 in compiler.cfg.stacks.uninitialized for details. */
 232
 233 struct call_frame_scrubber {
 234         factor_vm *parent;
 235         context *ctx;
 236
 237         explicit call_frame_scrubber(factor_vm *parent_, context *ctx_) :
 238                 parent(parent_), ctx(ctx_) {}
 239
 240         void operator()(stack_frame *frame)
 241         {
 242                 cell return_address = parent->frame_offset(frame);
 243                 if(return_address == (cell)-1)
 244                         return;
 245
 246                 code_block *compiled = parent->frame_code(frame);
 247                 gc_info *info = compiled->block_gc_info();
 248
 249                 FACTOR_ASSERT(return_address < compiled->size());
 250                 cell index = info->return_address_index(return_address);
 251                 if(index != (cell)-1)
 252                         ctx->scrub_stacks(info,index);
 253         }
 254 };
 255
 256 void factor_vm::scrub_context(context *ctx)
 257 {
 258         call_frame_scrubber scrubber(this,ctx);
 259         iterate_callstack(ctx,scrubber);
 260 }
 261
 262 void factor_vm::scrub_contexts()
 263 {
 264         std::set<context *>::const_iterator begin = active_contexts.begin();
 265         std::set<context *>::const_iterator end = active_contexts.end();
 266         while(begin != end)
 267         {
 268                 scrub_context(*begin);
 269                 begin++;
 270         }
 271 }
 272
 273 void factor_vm::primitive_minor_gc()
 274 {
 275         scrub_contexts();
 276
 277         gc(collect_nursery_op,
 278                 0, /* requested size */
 279                 true /* trace contexts? */);
 280 }
 281
 282 void factor_vm::primitive_full_gc()
 283 {
 284         gc(collect_full_op,
 285                 0, /* requested size */
 286                 true /* trace contexts? */);
 287 }
 288
 289 void factor_vm::primitive_compact_gc()
 290 {
 291         gc(collect_compact_op,
 292                 0, /* requested size */
 293                 true /* trace contexts? */);
 294 }
 295
 296 /*
 297  * It is up to the caller to fill in the object's fields in a meaningful
 298  * fashion!
 299  */
 300 object *factor_vm::allot_large_object(cell type, cell size)
 301 {
 302         /* If tenured space does not have enough room, collect and compact */
 303         cell requested_size = size + data->high_water_mark();
 304         if(!data->tenured->can_allot_p(requested_size))
 305         {
 306                 primitive_compact_gc();
 307
 308                 /* If it still won't fit, grow the heap */
 309                 if(!data->tenured->can_allot_p(requested_size))
 310                 {
 311                         gc(collect_growing_heap_op,
 312                                 size, /* requested size */
 313                                 true /* trace contexts? */);
 314                 }
 315         }
 316
 317         object *obj = data->tenured->allot(size);
 318
 319         /* Allows initialization code to store old->new pointers
 320         without hitting the write barrier in the common case of
 321         a nursery allocation */
 322         write_barrier(obj,size);
 323
 324         obj->initialize(type);
 325         return obj;
 326 }
 327
 328 void factor_vm::primitive_enable_gc_events()
 329 {
 330         gc_events = new std::vector<gc_event>();
 331 }
 332
 333 void factor_vm::primitive_disable_gc_events()
 334 {
 335         if(gc_events)
 336         {
 337                 growable_array result(this);
 338
 339                 std::vector<gc_event> *gc_events = this->gc_events;
 340                 this->gc_events = NULL;
 341
 342                 std::vector<gc_event>::const_iterator iter = gc_events->begin();
 343                 std::vector<gc_event>::const_iterator end = gc_events->end();
 344
 345                 for(; iter != end; iter++)
 346                 {
 347                         gc_event event = *iter;
 348                         byte_array *obj = byte_array_from_value(&event);
 349                         result.add(tag<byte_array>(obj));
 350                 }
 351
 352                 result.trim();
 353                 ctx->push(result.elements.value());
 354
 355                 delete this->gc_events;
 356         }
 357         else
 358                 ctx->push(false_object);
 359 }
 360
 361 }