query dba_free_space is slowly

 our customer use 10.2.0.4 in linux.

they find sql :

 select count(*) from dba_free_space is slowly, about 10  minute , it return about 193505 rows

but this sql:

select count(*) from dba_data_files is normal, about some second,it return about  43 row;

so i did this check.

do a 10046 trace . made a very big trace file,nearly about 100M  trace file ,

so i did a  tkprof it made a trace file:

############################
select count(*)
from
 dba_free_space call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.01       0.02          0          2          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        2     57.97     917.31      68849     133011        573           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------