Function base_block_alloc

deps/jemalloc/src/base.c:247–301

* Allocate a block of virtual memory that is large enough to start with a * base_block_t header, followed by an object of specified size and alignment. * On success a pointer to the initialized base_block_t header is returned. */

 * On success a pointer to the initialized base_block_t header is returned.
 */
static base_block_t *
base_block_alloc(tsdn_t *tsdn, base_t *base, extent_hooks_t *extent_hooks,
    unsigned ind, pszind_t *pind_last, size_t *extent_sn_next, size_t size,
    size_t alignment) {
	alignment = ALIGNMENT_CEILING(alignment, QUANTUM);
	size_t usize = ALIGNMENT_CEILING(size, alignment);
	size_t header_size = sizeof(base_block_t);
	size_t gap_size = ALIGNMENT_CEILING(header_size, alignment) -
	    header_size;
	/*
	 * Create increasingly larger blocks in order to limit the total number
	 * of disjoint virtual memory ranges.  Choose the next size in the page
	 * size class series (skipping size classes that are not a multiple of
	 * HUGEPAGE), or a size large enough to satisfy the requested size and
	 * alignment, whichever is larger.
	 */
	size_t min_block_size = HUGEPAGE_CEILING(sz_psz2u(header_size + gap_size
	    + usize));
	pszind_t pind_next = (*pind_last + 1 < sz_psz2ind(SC_LARGE_MAXCLASS)) ?
	    *pind_last + 1 : *pind_last;
	size_t next_block_size = HUGEPAGE_CEILING(sz_pind2sz(pind_next));
	size_t block_size = (min_block_size > next_block_size) ? min_block_size
	    : next_block_size;
	base_block_t *block = (base_block_t *)base_map(tsdn, extent_hooks, ind,
	    block_size);
	if (block == NULL) {
		return NULL;
	}

	if (metadata_thp_madvise()) {
		void *addr = (void *)block;
		assert(((uintptr_t)addr & HUGEPAGE_MASK) == 0 &&
		    (block_size & HUGEPAGE_MASK) == 0);
		if (opt_metadata_thp == metadata_thp_always) {
			pages_huge(addr, block_size);
		} else if (opt_metadata_thp == metadata_thp_auto &&
		    base != NULL) {
			/* base != NULL indicates this is not a new base. */
			malloc_mutex_lock(tsdn, &base->mtx);
			base_auto_thp_switch(tsdn, base);
			if (base->auto_thp_switched) {
				pages_huge(addr, block_size);
			}
			malloc_mutex_unlock(tsdn, &base->mtx);
		}
	}

	*pind_last = sz_psz2ind(block_size);
	block->size = block_size;
	block->next = NULL;
	assert(block_size >= header_size);
	base_extent_init(extent_sn_next, &block->extent,
	    (void *)((uintptr_t)block + header_size), block_size - header_size);
	return block;
}

/*
 * Allocate an extent that is at least as large as specified size, with