The single-stream TCP throughput in the TX subgroup is degraded for guest virtual machines running Oracle Unbreakable Enterprise Kernel (UEK) Release 4.
Workaround: This issue occurs because UEK Release 4 includes support for the TCP Small Queues (TSQ) mechanism. To resolve this issue, you can configure the guest virtual machine with the following command:
echo 1048576 > /proc/sys/net/ipv4/tcp_limit_output_bytes
Bug 22546060