​Ring Size

If packet drops are seen in ethtool -S <ethX> counters (rx_​dropped, rx_​dropped.nic) or there is suspected cache pressure with multiple queues active, try adjusting the ring size from the default value.

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

If it is suspected that buffer space allocation is causing packet drops at the current interrupt rate, you might try raising or lowering the values to check for improvement. Then, continue a binary search until you achieve optimal performance.

If cache pressure is suspected (with many queues active) reducing buffers from default can help Intel® Data Direct I/O (Intel® DDIO) operate more efficiently. Intel recommends trying 256 or 512 per queue, being aware that an increase in interrupt rate via ethtool -C might be necessary to avoid an increase in rx_​dropped rate.

• ​​To set ring size to a fixed value: ethtool -G <ethX> rx 256 tx 256 Note:To fix Rx packet drops found with 'ethtool -S <ethX> | grep drop', consider increasing the ring size to 4096. Experiment to find the best setting for the workload but watch out for excessive memory usage with higher values.