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Fix mark pattern updating for generational whippet

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After a minor collection, we were erroneously failing to sweep dead
objects with the survivor tag.
This commit is contained in:
Andy Wingo 2022-08-03 12:06:19 +02:00
parent 0210a8caf0
commit 96b68095b7
1 changed files with 13 additions and 12 deletions
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25
whippet.h
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@ -1032,6 +1032,7 @@ heap_object_is_young(struct heap *heap, struct gcobj *obj) {
static void mark_space_trace_generational_roots(struct mark_space *space, static void mark_space_trace_generational_roots(struct mark_space *space,
struct heap *heap) { struct heap *heap) {
ASSERT(!space->evacuating);
uint8_t live_tenured_mask = space->live_mask; uint8_t live_tenured_mask = space->live_mask;
for (size_t s = 0; s < space->nslabs; s++) { for (size_t s = 0; s < space->nslabs; s++) {
struct slab *slab = &space->slabs[s]; struct slab *slab = &space->slabs[s];
@ -1045,7 +1046,7 @@ static void mark_space_trace_generational_roots(struct mark_space *space,
// We could accelerate this but GRANULES_PER_REMSET_BYTE is 16 // We could accelerate this but GRANULES_PER_REMSET_BYTE is 16
// on 64-bit hosts, so maybe it's not so important. // on 64-bit hosts, so maybe it's not so important.
for (size_t granule = base; granule < limit; granule++) { for (size_t granule = base; granule < limit; granule++) {
if (slab->metadata[granule] & live_tenured_mask) { if (slab->metadata[granule] & space->live_mask) {
struct block *block0 = &slab->blocks[0]; struct block *block0 = &slab->blocks[0];
uintptr_t addr = ((uintptr_t)block0->data) + granule * GRANULE_SIZE; uintptr_t addr = ((uintptr_t)block0->data) + granule * GRANULE_SIZE;
struct gcobj *obj = (struct gcobj*)addr; struct gcobj *obj = (struct gcobj*)addr;
@ -1141,9 +1142,13 @@ static uint64_t broadcast_byte(uint8_t byte) {
return result * 0x0101010101010101ULL; return result * 0x0101010101010101ULL;
} }
static void rotate_mark_bytes(struct mark_space *space) { static void update_mark_patterns(struct mark_space *space,
space->live_mask = rotate_dead_survivor_marked(space->live_mask); int advance_mark_mask) {
space->marked_mask = rotate_dead_survivor_marked(space->marked_mask); uint8_t survivor_mask = space->marked_mask;
uint8_t next_marked_mask = rotate_dead_survivor_marked(survivor_mask);
if (advance_mark_mask)
space->marked_mask = next_marked_mask;
space->live_mask = survivor_mask | next_marked_mask;
space->sweep_mask = broadcast_byte(space->live_mask); space->sweep_mask = broadcast_byte(space->live_mask);
} }
@ -1410,8 +1415,7 @@ static void mark_space_finish_gc(struct mark_space *space,
enum gc_kind gc_kind) { enum gc_kind gc_kind) {
space->evacuating = 0; space->evacuating = 0;
reset_sweeper(space); reset_sweeper(space);
if ((gc_kind & GC_KIND_FLAG_MINOR) == 0) update_mark_patterns(space, 0);
rotate_mark_bytes(space);
reset_statistics(space); reset_statistics(space);
release_evacuation_target_blocks(space); release_evacuation_target_blocks(space);
} }
@ -1426,6 +1430,7 @@ static void collect(struct mutator *mut) {
} }
DEBUG("start collect #%ld:\n", heap->count); DEBUG("start collect #%ld:\n", heap->count);
enum gc_kind gc_kind = determine_collection_kind(heap); enum gc_kind gc_kind = determine_collection_kind(heap);
update_mark_patterns(space, !(gc_kind & GC_KIND_FLAG_MINOR));
large_object_space_start_gc(lospace, gc_kind & GC_KIND_FLAG_MINOR); large_object_space_start_gc(lospace, gc_kind & GC_KIND_FLAG_MINOR);
tracer_prepare(heap); tracer_prepare(heap);
request_mutators_to_stop(heap); request_mutators_to_stop(heap);
@ -1906,12 +1911,8 @@ static int mark_space_init(struct mark_space *space, struct heap *heap) {
if (!slabs) if (!slabs)
return 0; return 0;
uint8_t dead = METADATA_BYTE_MARK_0; space->marked_mask = METADATA_BYTE_MARK_0;
uint8_t survived = METADATA_BYTE_MARK_1; update_mark_patterns(space, 0);
uint8_t marked = METADATA_BYTE_MARK_2;
space->marked_mask = marked;
space->live_mask = survived | marked;
rotate_mark_bytes(space);
space->slabs = slabs; space->slabs = slabs;
space->nslabs = nslabs; space->nslabs = nslabs;
space->low_addr = (uintptr_t) slabs; space->low_addr = (uintptr_t) slabs;