CPU SPEED limit allows to set CPU limit in terms of % of a single core, or as a fixed number of Hz.
--speed=XX% would set performance relative to one core. For example:
--speed=50% would mean 1/2 core.
--speed=100% would mean 1 core,
--speed=150% would mean 1.5 cores
--speed=XXmhz would automatically detect CPU speed of each core, and adjust the CPU scheduler to make sure user cannot go over that limit.
For example, on 1ghz CPU, setting of --speed=2ghz would mean 2 cores, while on 4ghz CPU same setting would mean 1/2 of a core.
This should allow hosting companies to set same approximate performance level limits across different hardware using single setting.
Note. We strongly recommend setting CPU speed limits not less than 100%. As such limits cause CPU context switching which leads to increased %sys.