Very(!) slow ramp down from high to low clock speeds leading to a significantly increased power cons

PowerMizer under linux is extremely slow. It takes about 35 (!!!) seconds to reduce clocks even if there is no GPU load.
I can’t post img currenly, so here is gif:

This is from 375 driver.

Under windows it’s working perfectly good:

I was taking a look @ power meter and it takes about 3 seconds to lower power consumption. So under windows it’s perfectly possible.

I’ve also checked system power consumption using blender 2.78. Under windows I get ~30W back (system) immediately after I stop moving viewport around, I even don’t have to wait 3 secs. Under linux: no way, have to wait 36 seconds. IMO this seems so badly done, that under linux power management works only if you do true desktop idle. I simply don’t understand why it can’t be fixed.