cpu performance improvement

[soldierofhell]

Hi,
I wonder if I can boost cpu performance and thus investigate custom build options. I noticed that by default enable_mkl_dnn flag is turned on. My question is: do I have to install oneDNN to make it really used? BTW I noticed there's other flag for XLA (also true by default) xla_cpu_use_mkl_dnn. How are they related?
And lastly, can I expect any improvement from setting --target_cpu_features to "native" while building from source?

Regards,