drupal identify which content type is not used I have a drupal existing project which is slow in performance and many irrelavent extra stuff. what aprroach is best where i can identify that which content type is used or not . Or we can say that which content type is used where

Similar for field/taxonomy that which field/taxonomy is associated with which content type.
Just go to http://example.com/admin/content as user 1 and filter content by content type. If there is nothing, then content type is not used. Note that there may be views or modules that expect some content types to exist, even if you are not using them at the moment, so always make a backup before dropping them.

For fields, go to http://example.com/admin/reports/fields - you will get a nice list what is used where.