C-c C-a uses AuCTeX's heuristics for deciding which list of commands to run. The usual case is to use the function
TeX-command-default which is defined in
tex-buf.el. So no,
latexmk is not used.
You can make
latexmk accessible from
C-c C-c by customizing
TeX-command-list. One possibility is to a add an element of the form
INS DEL :
Command: latexmk %s
How: Value Menu TeX-run-TeX
Create a process for NAME using COMMAND to format FILE with TeX.
Prompt: Toggle off (nil)
Modes: Value Menu All
INS DEL Lisp expression: :help
INS DEL Lisp expression: "Run latexmk."
("LaTeXmk" "latexmk %s" TeX-run-TeX nil t :help "Run latexmk.")
TeX-command-list. Once this is done, on typing
C-c C-c you can choose
LaTeXmk as the command to run. Next time you type
C-c C-c this will be offered as the default, so can be accepted with just
Look at the other elements in
TeX-command-list to get an idea of ways to pass further options to
latexmk should you need them.