I have asked this question first at StackOverflow.com .Got no answer there.

So the problem is that I tried to switch from DDS to KTX compressed textures. KTX(ETC1/ETC2) .I used Khronos libktx to load the files.The difference vs DDS (sing NVidia DDS loader) is huge!

On twitter I asked Khronos about this issue and they advised to check if my GPU supports KTX uncompression on which I really have no idea(Using OpenGL4.3 on NVidia Quadro4000 ).So any one here has a clue where is my problem.Or maybe KTX is indeed so slow! I event stripped off libktx code from needless branching but haven't solved the problem.To me it seem to be somewhere on the driver level.