}
	// Pull off the last entry in the cache.
	s := pp.mspancache.buf[pp.mspancache.len-1]
	pp.mspancache.len--
	return s
}

// freeMSpanLocked free an mspan object.
//
// h.lock must be held.
//
// freeMSpanLocked must be called on the system stack because
// its caller holds the heap lock. See mheap for details.
// Running on the system stack also ensures that we won't