Upstream various patches from tikv's fork#244

Closed

nrc wants to merge 7 commits intoGuillaumeGomez:masterfrom nrc:vendor-up

+417-6

Commits on Jan 23, 2020

add functions get_cpu_frequency/get_avg_load

lonng
authored and
Nick Cameron
committed
support retrieve network statistics

lonng
authored and
Nick Cameron
committed
support retrieve block device IO statistics

lonng
authored and
Nick Cameron
committed
support retrieve system wide configuration list

lonng
authored and
Nick Cameron
committed
wrap num_cpus/pnet_datalink/cache_size crates

lonng
authored and
Nick Cameron
committed
Fix io issue with modern Linux versions
Nick Cameron
committed
Add get_vendor_id function
Nick Cameron
committed