So im picking random pixel from animated TOP with TOPtoSHOP with crop parameter set to Pixel(U, V). And it cooks 30ms. 
I tested it with 6700k, 1080gtx and i get 7-8ms (wich is still too much)
What is wrong with it?
ColorPicker.toe (1.16 MB)
Downloading data from the GPU to the CPU is slow for two reasons. The first and biggest reason is that GPUs are highly pipelined. This means that when commands are sent to it they are put into a queue (pipeline) and won’t get executed for a while. So asking for an image from the GPU sends a command, which won’t get executed for a while after a bunch of other previous work the GPU has queued up gets executed. For example if the image you are wanting to download is rendered, it may not be finished rendering for another 20ms, (Even though the render itself only takes 1ms). So this means the download operation can not start until at least 20ms has elapsed. But even unchanging images will still take a while to download since there will be other tasks in the command queue that need to finish before the download operation can begin.
The second reason is that GPU->CPU transfers are slow, and in particular are very slow on Geforce cards (They are far faster on Quadro cards). This doesn’t matter so much if you are downloading small amounts of data though.
This is why the Faster next frame download mode is available in the TOP To CHOP. It avoids the stall waiting for the image to be ready to be downloaded since it doesn’t try to use the download data for 16->33ms, giving it time to arrive.