code: public static void clearSSTableReadMeter(String keyspace, String table, int generation)
      {
          String cql = "DELETE FROM system.%s WHERE keyspace_name=? AND columnfamily_name=? and generation=?";
          executeInternal(String.format(cql, SSTABLE_ACTIVITY_CF), keyspace, table, generation);
      }
docs: Clears persisted read rates from system.sstable_activity for SSTables that have been deleted.