I'm confused by pmap -x output for some time: there is a Anon column and multiple [anon] rows for Mapped file column. They refers to different things, I guess, because there are mapped files, such as libc.so.1, that has a non-zero value for Anon column; and there are rows which are mapped to [ anon ] but no value is displayed in Anon column.
In the maual, it says:
Anon is The number of pages of anonymous memory associated with the specified mapping
Memory not relating to any named object or file within the file system is reported as [ anon ]
I'm kind of confused. Could anyone clarify this a bit?