Check If CPU is Being Throttled
If you want to see if your cooling solution is enough for your CPU to work at 100%, you can check it's current frequency by running:
sudo cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
You can compare this number (which is a Khz integer) against the maximum possible frequency of your CPU (which is also in Khz):
sudo cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
Please bear in mind that the "max frequency" listed for Intel is actually the max turbo frequency.
Testing With My Hardware
I was rather surprised that my Arctic Freezer 7 Pro Rev2, which cost me £10 when I bought it a while back, is able to keep my Intel i5 4670k boosted to just over 3.6ghz whilst all 4 cores were running at 100% converting a video with ffmpeg. For reference, the base frequency on that is 3.4 Ghz and the max turbo frequency is 3.8 Ghz.