CPU_TIME is always zero

Hi.

On my Linux boxs in userstats the CPU_TIME value is always zero. Is it meant so or I compiled something wrongly?

*************************** 8. row ***************************
                  USER: gb_orange111
     TOTAL_CONNECTIONS: 10
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 4
             BUSY_TIME: 0
              CPU_TIME: 0
        BYTES_RECEIVED: 20303
            BYTES_SENT: 161335
  BINLOG_BYTES_WRITTEN: 0
          ROWS_FETCHED: 499
          ROWS_UPDATED: 10
       TABLE_ROWS_READ: 563
       SELECT_COMMANDS: 71
       UPDATE_COMMANDS: 10
        OTHER_COMMANDS: 20
   COMMIT_TRANSACTIONS: 78
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 59

Percona version - Percona-Server-5.1.62.tar.gz
Gentoo with kernel 3.3.3.