1 /* -----------------------------------------------------------------------*-c-*-
3 * (c) The GHC Team 1998-2006
5 * Generational garbage collector: scavenging functions
7 * Documentation on the architecture of the Garbage Collector can be
8 * found in the online commentary:
10 * http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/GC
12 * ---------------------------------------------------------------------------*/
14 // This file is #included into Scav.c, twice: firstly with PARALLEL_GC
15 // defined, the second time without.
18 #define scavenge_block(a,b) scavenge_block1(a,b)
19 #define evacuate(a) evacuate1(a)
23 #undef recordMutableGen_GC
26 static void scavenge_block (bdescr *bd, StgPtr scan);
28 /* -----------------------------------------------------------------------------
29 Scavenge a block from the given scan pointer up to bd->free.
31 evac_step is set by the caller to be either zero (for a step in a
32 generation < N) or G where G is the generation of the step being
35 We sometimes temporarily change evac_step back to zero if we're
36 scavenging a mutable object where eager promotion isn't such a good
38 -------------------------------------------------------------------------- */
41 scavenge_block (bdescr *bd, StgPtr scan)
45 step *saved_evac_step;
46 rtsBool saved_eager_promotion;
51 debugTrace(DEBUG_gc, "scavenging block %p (gen %d, step %d) @ %p",
52 bd->start, bd->gen_no, bd->step->no, scan);
54 gct->evac_step = bd->step;
55 saved_evac_step = gct->evac_step;
56 saved_eager_promotion = gct->eager_promotion;
57 gct->failed_to_evac = rtsFalse;
59 ws = &gct->steps[bd->step->abs_no];
61 // we might be evacuating into the very object that we're
62 // scavenging, so we have to check the real bd->free pointer each
63 // time around the loop.
64 while (p < bd->free || (bd == ws->todo_bd && p < ws->todo_free)) {
66 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
67 info = get_itbl((StgClosure *)p);
69 ASSERT(gct->thunk_selector_depth == 0);
77 StgMVar *mvar = ((StgMVar *)p);
78 gct->eager_promotion = rtsFalse;
79 evacuate((StgClosure **)&mvar->head);
80 evacuate((StgClosure **)&mvar->tail);
81 evacuate((StgClosure **)&mvar->value);
82 gct->eager_promotion = saved_eager_promotion;
84 if (gct->failed_to_evac) {
85 mvar->header.info = &stg_MVAR_DIRTY_info;
87 mvar->header.info = &stg_MVAR_CLEAN_info;
89 p += sizeofW(StgMVar);
94 scavenge_fun_srt(info);
95 evacuate(&((StgClosure *)p)->payload[1]);
96 evacuate(&((StgClosure *)p)->payload[0]);
97 p += sizeofW(StgHeader) + 2;
101 scavenge_thunk_srt(info);
102 evacuate(&((StgThunk *)p)->payload[1]);
103 evacuate(&((StgThunk *)p)->payload[0]);
104 p += sizeofW(StgThunk) + 2;
108 evacuate(&((StgClosure *)p)->payload[1]);
109 evacuate(&((StgClosure *)p)->payload[0]);
110 p += sizeofW(StgHeader) + 2;
114 scavenge_thunk_srt(info);
115 evacuate(&((StgThunk *)p)->payload[0]);
116 p += sizeofW(StgThunk) + 1;
120 scavenge_fun_srt(info);
122 evacuate(&((StgClosure *)p)->payload[0]);
123 p += sizeofW(StgHeader) + 1;
127 scavenge_thunk_srt(info);
128 p += sizeofW(StgThunk) + 1;
132 scavenge_fun_srt(info);
134 p += sizeofW(StgHeader) + 1;
138 scavenge_thunk_srt(info);
139 p += sizeofW(StgThunk) + 2;
143 scavenge_fun_srt(info);
145 p += sizeofW(StgHeader) + 2;
149 scavenge_thunk_srt(info);
150 evacuate(&((StgThunk *)p)->payload[0]);
151 p += sizeofW(StgThunk) + 2;
155 scavenge_fun_srt(info);
157 evacuate(&((StgClosure *)p)->payload[0]);
158 p += sizeofW(StgHeader) + 2;
162 scavenge_fun_srt(info);
169 scavenge_thunk_srt(info);
170 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
171 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
172 evacuate((StgClosure **)p);
174 p += info->layout.payload.nptrs;
185 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
186 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
187 evacuate((StgClosure **)p);
189 p += info->layout.payload.nptrs;
194 StgBCO *bco = (StgBCO *)p;
195 evacuate((StgClosure **)&bco->instrs);
196 evacuate((StgClosure **)&bco->literals);
197 evacuate((StgClosure **)&bco->ptrs);
203 if (bd->gen_no != 0) {
206 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
207 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
208 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
211 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
213 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
215 // We pretend that p has just been created.
216 LDV_RECORD_CREATE((StgClosure *)p);
219 case IND_OLDGEN_PERM:
220 evacuate(&((StgInd *)p)->indirectee);
221 p += sizeofW(StgInd);
226 gct->eager_promotion = rtsFalse;
227 evacuate(&((StgMutVar *)p)->var);
228 gct->eager_promotion = saved_eager_promotion;
230 if (gct->failed_to_evac) {
231 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
233 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
235 p += sizeofW(StgMutVar);
239 case SE_CAF_BLACKHOLE:
242 p += BLACKHOLE_sizeW();
247 StgSelector *s = (StgSelector *)p;
248 evacuate(&s->selectee);
249 p += THUNK_SELECTOR_sizeW();
253 // A chunk of stack saved in a heap object
256 StgAP_STACK *ap = (StgAP_STACK *)p;
259 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
260 p = (StgPtr)ap->payload + ap->size;
265 p = scavenge_PAP((StgPAP *)p);
269 p = scavenge_AP((StgAP *)p);
274 p += arr_words_sizeW((StgArrWords *)p);
277 case MUT_ARR_PTRS_CLEAN:
278 case MUT_ARR_PTRS_DIRTY:
283 // We don't eagerly promote objects pointed to by a mutable
284 // array, but if we find the array only points to objects in
285 // the same or an older generation, we mark it "clean" and
286 // avoid traversing it during minor GCs.
287 gct->eager_promotion = rtsFalse;
288 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
289 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
290 evacuate((StgClosure **)p);
292 gct->eager_promotion = saved_eager_promotion;
294 if (gct->failed_to_evac) {
295 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
297 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
300 gct->failed_to_evac = rtsTrue; // always put it on the mutable list.
304 case MUT_ARR_PTRS_FROZEN:
305 case MUT_ARR_PTRS_FROZEN0:
310 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
311 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
312 evacuate((StgClosure **)p);
315 // If we're going to put this object on the mutable list, then
316 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
317 if (gct->failed_to_evac) {
318 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
320 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
327 StgTSO *tso = (StgTSO *)p;
329 gct->eager_promotion = rtsFalse;
331 gct->eager_promotion = saved_eager_promotion;
333 if (gct->failed_to_evac) {
334 tso->flags |= TSO_DIRTY;
336 tso->flags &= ~TSO_DIRTY;
339 gct->failed_to_evac = rtsTrue; // always on the mutable list
344 case TVAR_WATCH_QUEUE:
346 StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
348 evacuate((StgClosure **)&wq->closure);
349 evacuate((StgClosure **)&wq->next_queue_entry);
350 evacuate((StgClosure **)&wq->prev_queue_entry);
351 gct->evac_step = saved_evac_step;
352 gct->failed_to_evac = rtsTrue; // mutable
353 p += sizeofW(StgTVarWatchQueue);
359 StgTVar *tvar = ((StgTVar *) p);
361 evacuate((StgClosure **)&tvar->current_value);
362 evacuate((StgClosure **)&tvar->first_watch_queue_entry);
363 gct->evac_step = saved_evac_step;
364 gct->failed_to_evac = rtsTrue; // mutable
365 p += sizeofW(StgTVar);
371 StgTRecHeader *trec = ((StgTRecHeader *) p);
373 evacuate((StgClosure **)&trec->enclosing_trec);
374 evacuate((StgClosure **)&trec->current_chunk);
375 evacuate((StgClosure **)&trec->invariants_to_check);
376 gct->evac_step = saved_evac_step;
377 gct->failed_to_evac = rtsTrue; // mutable
378 p += sizeofW(StgTRecHeader);
385 StgTRecChunk *tc = ((StgTRecChunk *) p);
386 TRecEntry *e = &(tc -> entries[0]);
388 evacuate((StgClosure **)&tc->prev_chunk);
389 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
390 evacuate((StgClosure **)&e->tvar);
391 evacuate((StgClosure **)&e->expected_value);
392 evacuate((StgClosure **)&e->new_value);
394 gct->evac_step = saved_evac_step;
395 gct->failed_to_evac = rtsTrue; // mutable
396 p += sizeofW(StgTRecChunk);
400 case ATOMIC_INVARIANT:
402 StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
404 evacuate(&invariant->code);
405 evacuate((StgClosure **)&invariant->last_execution);
406 gct->evac_step = saved_evac_step;
407 gct->failed_to_evac = rtsTrue; // mutable
408 p += sizeofW(StgAtomicInvariant);
412 case INVARIANT_CHECK_QUEUE:
414 StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
416 evacuate((StgClosure **)&queue->invariant);
417 evacuate((StgClosure **)&queue->my_execution);
418 evacuate((StgClosure **)&queue->next_queue_entry);
419 gct->evac_step = saved_evac_step;
420 gct->failed_to_evac = rtsTrue; // mutable
421 p += sizeofW(StgInvariantCheckQueue);
426 barf("scavenge: unimplemented/strange closure type %d @ %p",
431 * We need to record the current object on the mutable list if
432 * (a) It is actually mutable, or
433 * (b) It contains pointers to a younger generation.
434 * Case (b) arises if we didn't manage to promote everything that
435 * the current object points to into the current generation.
437 if (gct->failed_to_evac) {
438 gct->failed_to_evac = rtsFalse;
439 if (bd->gen_no > 0) {
440 recordMutableGen_GC((StgClosure *)q, &generations[bd->gen_no]);
449 debugTrace(DEBUG_gc, " scavenged %ld bytes",
450 (unsigned long)((bd->free - scan) * sizeof(W_)));
453 #undef scavenge_block