​Ring Size

If you are seeing rx_​dropped counters in ethtool -S ethX (rx_​dropped, rx_​dropped.nic), or suspect cache pressure with multiple queues active, you might try adjusting the ring size from the default value. The default value is 512, the max is 4096.

• ​​To check the current values: ethtool -g ethX

If it is suspected that lack of buffering is causing drops at the current interrupt rate, you might try the maximum first, then the minimum, then continue on in a binary search until you see optimal performance.

If cache pressure is suspected (many queues active) reducing buffers from default can help Intel® Data Direct I/O (Intel® DDIO) operate with better efficiently. Intel recommends trying 128 or 256 per queue, being aware that an increase in interrupt rate via ethtool -C might be necessary to avoid an increase in rx_​dropped.

• ​​To set ring size to fixed value: ethtool -G eth12 rx 256 tx 256