postgresql.conf setting for max_fsm_pages

Hi All,

I am new in using postgresSQL, I now support a system that been
running on postgressql. Recently I found that the database are
consuming the diskspace rapidly, it starting from 9GB and it now grow
until 40GB within 4-5 month.

I try to do a full vacuum to the database but then i get this error

NOTICE: number of page slots needed (1277312) exceeds max_fsm_pages
(819200)
HINT: Consider increasing the configuration parameter "max_fsm_pages"
to a value over 1277312.
VACUUM

I did a vacuum verbose.
postgres=# vacuum verbose;

and below is the result i got.

INFO: free space map contains 1045952 pages in 1896 relations
DETAIL: A total of 819200 page slots are in use (including overhead).
1114192 page slots are required to track all free space.
Current limits are: 819200 page slots, 2000 relations, using 5007 kB.
NOTICE: number of page slots needed (1114192) exceeds max_fsm_pages
(819200)
HINT: Consider increasing the configuration parameter "max_fsm_pages"
to a value over 1114192.
VACUUM

As from the postgres documentation, it was advice to set it to 20K to
200K which my current setting is set to 819200 which also over 200K
already, so i just wonder what is the max number that i can set for
the max_fsm_pages?

Is that any impact if i set the value to over 2M ?

Thanks.

Regards,
Chio Chuan