in the pytorch CPU-only wheels, we actually do statically link MKL and MKLDNN so that the unneeded symbols are stripped out, hence their respective sizes.
The reality is, whether you use ONNX Runtime or PyTorch wheel, if you want MKL and MKLDNN, you will pay the cost of the size of the routines they ship, and their BLAS routines and their Convolution routines are large (they ship a lot of precompiled codegen).
The PyTorch CPU-only wheel today ships at a size of 127.3MB for PyTorch 1.5.0