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pcc: Tail-call an out-of-memory handler if allocation fails

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This commit is contained in:
Andy Wingo 2025-04-23 10:47:32 +02:00
parent 6032adede9
commit a0148d4b38
2 changed files with 49 additions and 27 deletions
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4
src/copy-space.h
View file

@ -287,7 +287,7 @@ copy_space_request_release_memory(struct copy_space *space, size_t bytes) {
return atomic_fetch_add(&space->bytes_to_page_out, bytes) + bytes;
}
static int
static ssize_t
copy_space_page_out_blocks_until_memory_released(struct copy_space *space) {
ssize_t pending = atomic_load(&space->bytes_to_page_out);
struct gc_lock lock = copy_space_lock(space);
@ -299,7 +299,7 @@ copy_space_page_out_blocks_until_memory_released(struct copy_space *space) {
- COPY_SPACE_BLOCK_SIZE);
}
gc_lock_release(&lock);
return pending <= 0;
return pending;
}
static ssize_t

72
src/pcc.c
View file

@ -73,6 +73,7 @@ struct gc_heap {
struct gc_heap_sizer sizer;
struct gc_event_listener event_listener;
void *event_listener_data;
void* (*allocation_failure)(struct gc_heap *, size_t);
};
#define HEAP_EVENT(heap, event, ...) do { \
@ -862,10 +863,26 @@ copy_spaces_allocated_bytes(struct gc_heap *heap)
: heap_mono_space(heap)->allocated_bytes_at_last_gc;
}
static enum gc_collection_kind
static int
resolve_pending_large_allocation_and_compute_success(struct gc_heap *heap,
int is_minor_gc) {
struct copy_space *space = heap_resizable_space(heap);
ssize_t deficit = copy_space_page_out_blocks_until_memory_released(space);
if (is_minor_gc)
return 1;
if (deficit <= 0)
return copy_space_can_allocate(space, gc_allocator_large_threshold());
deficit = align_up(deficit, COPY_SPACE_BLOCK_SIZE);
if (heap->sizer.policy == GC_HEAP_SIZE_FIXED)
return 0;
resize_heap(heap, heap->size + deficit);
return 1;
}
static int
collect(struct gc_mutator *mut,
enum gc_collection_kind requested_kind) GC_NEVER_INLINE;
static enum gc_collection_kind
static int
collect(struct gc_mutator *mut, enum gc_collection_kind requested_kind) {
struct gc_heap *heap = mutator_heap(mut);
struct large_object_space *lospace = heap_large_object_space(heap);
@ -920,32 +937,28 @@ collect(struct gc_mutator *mut, enum gc_collection_kind requested_kind) {
HEAP_EVENT(heap, live_data_size, live_size);
gc_heap_sizer_on_gc(heap->sizer, heap->size, live_size, pause_ns,
resize_heap);
{
struct copy_space *space = heap_resizable_space(heap);
if (!copy_space_page_out_blocks_until_memory_released(space)
&& heap->sizer.policy == GC_HEAP_SIZE_FIXED) {
fprintf(stderr, "ran out of space, heap size %zu\n", heap->size);
GC_CRASH();
}
}
int success =
resolve_pending_large_allocation_and_compute_success(heap, is_minor_gc);
HEAP_EVENT(heap, restarting_mutators);
allow_mutators_to_continue(heap);
return gc_kind;
return success;
}
static void trigger_collection(struct gc_mutator *mut,
enum gc_collection_kind requested_kind) {
static int trigger_collection(struct gc_mutator *mut,
enum gc_collection_kind requested_kind) {
struct gc_heap *heap = mutator_heap(mut);
copy_space_allocator_finish(&mut->allocator, heap_allocation_space(heap));
if (GC_GENERATIONAL)
gc_field_set_writer_release_buffer(mutator_field_logger(mut));
heap_lock(heap);
int prev_kind = -1;
int success = 1;
while (mutators_are_stopping(heap))
prev_kind = pause_mutator_for_collection(heap, mut);
if (prev_kind < (int)requested_kind)
collect(mut, requested_kind);
success = collect(mut, requested_kind);
heap_unlock(heap);
return success;
}
void gc_collect(struct gc_mutator *mut, enum gc_collection_kind kind) {
@ -955,13 +968,18 @@ void gc_collect(struct gc_mutator *mut, enum gc_collection_kind kind) {
static void* allocate_large(struct gc_mutator *mut, size_t size) {
struct gc_heap *heap = mutator_heap(mut);
struct large_object_space *space = heap_large_object_space(heap);
struct copy_space *copy_space = heap_resizable_space(heap);
size_t npages = large_object_space_npages(space, size);
size_t page_bytes = npages << space->page_size_log2;
copy_space_request_release_memory(copy_space, page_bytes);
if (copy_space_page_out_blocks_until_memory_released(copy_space) > 0
&& !trigger_collection(mut, GC_COLLECTION_COMPACTING)) {
copy_space_maybe_reacquire_memory(copy_space, page_bytes);
return heap->allocation_failure(heap, size);
}
copy_space_request_release_memory(heap_resizable_space(heap),
npages << space->page_size_log2);
while (!copy_space_page_out_blocks_until_memory_released(heap_resizable_space(heap)))
trigger_collection(mut, GC_COLLECTION_COMPACTING);
atomic_fetch_add(&heap->large_object_pages, npages);
void *ret = large_object_space_alloc(space, npages, GC_TRACE_PRECISELY);
@ -974,10 +992,6 @@ static void* allocate_large(struct gc_mutator *mut, size_t size) {
return ret;
}
static void get_more_empty_blocks_for_mutator(void *mut) {
trigger_collection(mut, GC_COLLECTION_MINOR);
}
void* gc_allocate_slow(struct gc_mutator *mut, size_t size,
enum gc_allocation_kind kind) {
if (GC_UNLIKELY(kind != GC_ALLOCATION_TAGGED
@ -996,10 +1010,11 @@ void* gc_allocate_slow(struct gc_mutator *mut, size_t size,
ret = copy_space_allocate(&mut->allocator,
heap_allocation_space(mutator_heap(mut)),
size);
if (gc_ref_is_null(ret))
trigger_collection(mut, GC_COLLECTION_MINOR);
else
if (!gc_ref_is_null(ret))
break;
if (trigger_collection(mut, GC_COLLECTION_MINOR))
continue;
return mutator_heap(mut)->allocation_failure(mutator_heap(mut), size);
}
return gc_ref_heap_object(ret);
@ -1178,6 +1193,12 @@ static void set_heap_size_from_thread(struct gc_heap *heap, size_t size) {
pthread_mutex_unlock(&heap->lock);
}
static void* allocation_failure(struct gc_heap *heap, size_t size) {
fprintf(stderr, "ran out of space, heap size %zu\n", heap->size);
GC_CRASH();
return NULL;
}
static int heap_init(struct gc_heap *heap, const struct gc_options *options) {
// *heap is already initialized to 0.
@ -1214,6 +1235,7 @@ static int heap_init(struct gc_heap *heap, const struct gc_options *options) {
allocation_counter_from_thread,
set_heap_size_from_thread,
heap->background_thread);
heap->allocation_failure = allocation_failure;
return 1;
}