Inquiry for using a compressed texture format


I know as the benefit of using compressed texture is reducing memory usage and bandwidth when the texture is uploaded on the Mali.

For comparing between uncompressed and compressed, I measured the duration of glDrawElements() for each format

start = GfxPerfGetMSec();
glDrawElements(GL_TRIANGLES, cnt * 6, GL_UNSIGNED_BYTE, 0);
end = GfxPerfGetMSec();


Because the uploaded compressed texture data size in GPU is less than the uploaded uncompressed texture data size in GPU like below

I think that the performance of using compressed texture data should be better than the performance of using uncompressed texture.

But the result is that the performance decreases when using compressed texture.

Surely, each GPU architecture is different each vendor 

But, When other vendor's GPU uses the compressed texture, the performance is improved dramatically(same test)

Although Mali need more resource(compute, decompressing) for decompressing, I think that it should be processed fast and improved slightly than using uncompressed texture.

Also Because the Mali processes the compressed texture in HW, i think that it can process the compressed texture quickly

Could you explain why the performance of using compressed texture on Mali decrease?