How to ensure that a code in a Cortex-A is running at the maximum CPU frequency

When I run a code in C I need to run every 30ms a set of calculations that transforms an image and that is taking up to 100ms which forces me to discard 3 out of every 4 frames I get.

How can I ensure that the CPU clock frequency is at its maximum?

I'm using a Cortex-A53 that runs between 400Mhz and 1400Mhz.

Below is the result of the command cat /proc/cpuinfo

Processor       : ARMv7 Processor rev 3 (v7l)
processor       : 0
BogoMIPS        : 1594.36

processor       : 1
BogoMIPS        : 1594.36

processor       : 2
BogoMIPS        : 1594.36

processor       : 3
BogoMIPS        : 1594.36

processor       : 4
BogoMIPS        : 1601.53

processor       : 5
BogoMIPS        : 1594.36

processor       : 6
BogoMIPS        : 1594.36

processor       : 7
BogoMIPS        : 1594.36

I've tried to use the code suggested in this link to know the processor speed, but I'm not able to compile it because I do not find the correct includes:

link

What would be the correct code to get the current CPU clock frequency and how to adjust at run time so that it uses the maximum?

I'm using Linux, with C ++ in GCC 4.9, on a Cortex-A53.