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Measure fragmentation as fraction of total heap size

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This allows a relatively more fragmented mark space if the majority of
the heap is taken up by lospace.
This commit is contained in:
Andy Wingo 2022-07-20 11:11:50 +02:00
parent 7af8bb6bd0
commit c998f1cd5c
1 changed files with 39 additions and 8 deletions
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47
whippet.h
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@ -305,6 +305,8 @@ struct heap {
long count;
struct mutator *deactivated_mutators;
struct tracer tracer;
double fragmentation_low_threshold;
double fragmentation_high_threshold;
};
struct mutator_mark_buf {
@ -771,6 +773,24 @@ static int maybe_grow_heap(struct heap *heap, enum gc_reason reason) {
return 0;
}
static double heap_fragmentation(struct heap *heap) {
struct mark_space *mark_space = heap_mark_space(heap);
size_t mark_space_blocks = mark_space->nslabs * NONMETA_BLOCKS_PER_SLAB;
mark_space_blocks -= atomic_load(&mark_space->unavailable_blocks_count);
size_t mark_space_granules = mark_space_blocks * GRANULES_PER_BLOCK;
size_t fragmentation_granules =
mark_space->fragmentation_granules_since_last_collection;
struct large_object_space *lospace = heap_large_object_space(heap);
size_t lospace_pages = lospace->total_pages - lospace->free_pages;
size_t lospace_granules =
lospace_pages << (lospace->page_size_log2 - GRANULE_SIZE_LOG_2);
size_t heap_granules = mark_space_granules + lospace_granules;
return ((double)fragmentation_granules) / heap_granules;
}
static void determine_collection_kind(struct heap *heap,
enum gc_reason reason) {
}
@ -792,9 +812,8 @@ static void collect(struct mutator *mut, enum gc_reason reason) {
finish_sweeping(mut);
wait_for_mutators_to_stop(heap);
double yield = space->granules_freed_by_last_collection * GRANULE_SIZE;
double fragmentation = space->fragmentation_granules_since_last_collection * GRANULE_SIZE;
double fragmentation = heap_fragmentation(heap);
yield /= SLAB_SIZE * space->nslabs;
fragmentation /= SLAB_SIZE * space->nslabs;
fprintf(stderr, "last gc yield: %f; fragmentation: %f\n", yield, fragmentation);
trace_mutator_roots_after_stop(heap);
trace_global_roots(heap);
@ -1239,6 +1258,23 @@ static struct slab* allocate_slabs(size_t nslabs) {
return (struct slab*) aligned_base;
}
static int heap_init(struct heap *heap, size_t size) {
// *heap is already initialized to 0.
pthread_mutex_init(&heap->lock, NULL);
pthread_cond_init(&heap->mutator_cond, NULL);
pthread_cond_init(&heap->collector_cond, NULL);
heap->size = size;
if (!tracer_init(heap))
abort();
heap->fragmentation_low_threshold = 0.05;
heap->fragmentation_high_threshold = 0.10;
return 1;
}
static int mark_space_init(struct mark_space *space, struct heap *heap) {
size_t size = align_up(heap->size, SLAB_SIZE);
size_t nslabs = size / SLAB_SIZE;
@ -1276,12 +1312,7 @@ static int initialize_gc(size_t size, struct heap **heap,
*heap = calloc(1, sizeof(struct heap));
if (!*heap) abort();
pthread_mutex_init(&(*heap)->lock, NULL);
pthread_cond_init(&(*heap)->mutator_cond, NULL);
pthread_cond_init(&(*heap)->collector_cond, NULL);
(*heap)->size = size;
if (!tracer_init(*heap))
if (!heap_init(*heap, size))
abort();
struct mark_space *space = heap_mark_space(*heap);