n -= uintptr(len(inUse) * 8)
	}
	sweep.active.end(sl)
	trace := traceAcquire()
	if trace.ok() {
		unlock(&h.lock)
		// Account for pages scanned but not reclaimed.
		trace.GCSweepSpan((n0 - nFreed) * pageSize)
		traceRelease(trace)
		lock(&h.lock)
	}

	assertLockHeld(&h.lock) // Must be locked on return.
	return nFreed
}