printk second output

Question

When I printk(KERN_INFO, ...), I get something like this:

<6>[116584.000183] ...

What is the number between the square brackets exactly?

Answer 1

It's a timestamp with microsecond resolution. See the printk source.

Answer 2

Seconds since startup. You can control whether this is shown with the CONFIG_PRINTK_TIME variable in kernel config.