The behavior is also controlled by the kernel command line
parameter printk.time=1. See Documentation/kernel-parameters.txt
+config PRINTK_PROCESS
+ bool "Show process information on printks"
+ depends on PRINTK
+ help
+ Selecting this option causes process to be
+ included in printk output. Or add printk.process=1 at boot-time.
+
config DEFAULT_MESSAGE_LOGLEVEL
int "Default message log level (1-7)"
range 1 7