Function _rpmalloc_span_map_aligned_count

source/extern/rpmalloc.c:1183–1218

Map an aligned set of spans, taking configured mapping granularity and the page size into account

//! Map an aligned set of spans, taking configured mapping granularity and the page size into account
static span_t*
_rpmalloc_span_map_aligned_count(heap_t* heap, size_t span_count) {
	//If we already have some, but not enough, reserved spans, release those to heap cache and map a new
	//full set of spans. Otherwise we would waste memory if page size > span size (huge pages)
	size_t aligned_span_count = _rpmalloc_span_align_count(span_count);
	size_t align_offset = 0;
	span_t* span = (span_t*)_rpmalloc_mmap(aligned_span_count * _memory_span_size, &align_offset);
	if (!span)
		return 0;
	_rpmalloc_span_initialize(span, aligned_span_count, span_count, align_offset);
	_rpmalloc_stat_inc(&_master_spans);
	if (span_count <= LARGE_CLASS_COUNT)
		_rpmalloc_stat_inc(&heap->span_use[span_count - 1].spans_map_calls);
	if (aligned_span_count > span_count) {
		span_t* reserved_spans = (span_t*)pointer_offset(span, span_count * _memory_span_size);
		size_t reserved_count = aligned_span_count - span_count;
		if (heap->spans_reserved) {
			_rpmalloc_span_mark_as_subspan_unless_master(heap->span_reserve_master, heap->span_reserve, heap->spans_reserved);
			_rpmalloc_heap_cache_insert(heap, heap->span_reserve);
		}
		if (reserved_count > _memory_heap_reserve_count) {
			// If huge pages or eager spam map count, the global reserve spin lock is held by caller, _rpmalloc_span_map
			rpmalloc_assert(atomic_load32(&_memory_global_lock) == 1, "Global spin lock not held as expected");
			size_t remain_count = reserved_count - _memory_heap_reserve_count;
			reserved_count = _memory_heap_reserve_count;
			span_t* remain_span = (span_t*)pointer_offset(reserved_spans, reserved_count * _memory_span_size);
			if (_memory_global_reserve) {
				_rpmalloc_span_mark_as_subspan_unless_master(_memory_global_reserve_master, _memory_global_reserve, _memory_global_reserve_count);
				_rpmalloc_span_unmap(_memory_global_reserve);
			}
			_rpmalloc_global_set_reserved_spans(span, remain_span, remain_count);
		}
		_rpmalloc_heap_set_reserved_spans(heap, span, reserved_spans, reserved_count);
	}
	return span;
}

//! Map in memory pages for the given number of spans (or use previously reserved pages)
static span_t*