"tx-nocache-copy" is a feature which bypasses local cache and writes user-space data directly into memory.
New kernels have this feature disabled by default, while on it comes enabled on some Linux distributions.
It is recommended to disable this feature, as it can harm performance.
To disable tx-nocache-copy, run:
# ethtool -K eth1 tx-nocache-copy off
To enable tx-nocache-copy, run:
# ethtool -K eth1 tx-nocache-copy on
To view current configuration, run:
# ethtool --show-offload eth1 | grep tx-nocache-copy