Function extent_alloc_dss

app/redis-6.2.6/deps/jemalloc/src/extent_dss.c:109–228

}

void *
extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
    size_t alignment, bool *zero, bool *commit) {
	extent_t *gap;

	cassert(have_dss);
	assert(size > 0);
	assert(alignment > 0);

	/*
	 * sbrk() uses a signed increment argument, so take care not to
	 * interpret a large allocation request as a negative increment.
	 */
	if ((intptr_t)size < 0) {
		return NULL;
	}

	gap = extent_alloc(tsdn, arena);
	if (gap == NULL) {
		return NULL;
	}

	extent_dss_extending_start();
	if (!atomic_load_b(&dss_exhausted, ATOMIC_ACQUIRE)) {
		/*
		 * The loop is necessary to recover from races with other
		 * threads that are using the DSS for something other than
		 * malloc.
		 */
		while (true) {
			void *max_cur = extent_dss_max_update(new_addr);
			if (max_cur == NULL) {
				goto label_oom;
			}

			/*
			 * Compute how much page-aligned gap space (if any) is
			 * necessary to satisfy alignment.  This space can be
			 * recycled for later use.
			 */
			void *gap_addr_page = (void *)(PAGE_CEILING(
			    (uintptr_t)max_cur));
			void *ret = (void *)ALIGNMENT_CEILING(
			    (uintptr_t)gap_addr_page, alignment);
			size_t gap_size_page = (uintptr_t)ret -
			    (uintptr_t)gap_addr_page;
			if (gap_size_page != 0) {
				extent_init(gap, arena, gap_addr_page,
				    gap_size_page, false, NSIZES,
				    arena_extent_sn_next(arena),
				    extent_state_active, false, true, true);
			}
			/*
			 * Compute the address just past the end of the desired
			 * allocation space.
			 */
			void *dss_next = (void *)((uintptr_t)ret + size);
			if ((uintptr_t)ret < (uintptr_t)max_cur ||