In Monero 0.11.0.0, a poolstate.bin file is not created in ~/.bitmonero, but was in previous versions ? Is this file missing, or is there any problem with my Monero setup ?
The poolstate.bin file used to contain the set of transactions which were not yet mined, known as the txpool. Monero 0.11.0.0 moved those transactions into the database, stored in ~/.bitmonero/lmdb, so the poolstate.bin file is now obsolete, and will thus not be created. A lack of poolstate.bin does not indicate anything wrong with monerod.
An old Monero install may still have this file, but it will only contain old transactions from before the change, and it may be safely deleted.