Function extents_first_fit_locked

deps/jemalloc/src/extent.c:442–486

* Do first-fit extent selection, i.e. select the oldest/lowest extent that is * large enough. */

 * large enough.
 */
static extent_t *
extents_first_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
    size_t size) {
	extent_t *ret = NULL;

	pszind_t pind = sz_psz2ind(extent_size_quantize_ceil(size));

	if (!maps_coalesce && !opt_retain) {
		/*
		 * No split / merge allowed (Windows w/o retain). Try exact fit
		 * only.
		 */
		return extent_heap_empty(&extents->heaps[pind]) ? NULL :
		    extent_heap_first(&extents->heaps[pind]);
	}

	for (pszind_t i = (pszind_t)bitmap_ffu(extents->bitmap,
	    &extents_bitmap_info, (size_t)pind);
	    i < SC_NPSIZES + 1;
	    i = (pszind_t)bitmap_ffu(extents->bitmap, &extents_bitmap_info,
	    (size_t)i+1)) {
		assert(!extent_heap_empty(&extents->heaps[i]));
		extent_t *extent = extent_heap_first(&extents->heaps[i]);
		assert(extent_size_get(extent) >= size);
		/*
		 * In order to reduce fragmentation, avoid reusing and splitting
		 * large extents for much smaller sizes.
		 *
		 * Only do check for dirty extents (delay_coalesce).
		 */
		if (extents->delay_coalesce &&
		    (sz_pind2sz(i) >> opt_lg_extent_max_active_fit) > size) {
			break;
		}
		if (ret == NULL || extent_snad_comp(extent, ret) < 0) {
			ret = extent;
		}
		if (i == SC_NPSIZES) {
			break;
		}
		assert(i < SC_NPSIZES);
	}

	return ret;
}

/*
 * Do first-fit extent selection, where the selection policy choice is