Christoph Lameter wrote:

If I use a large send queue

(echo 2000000 >/proc/sys/net/core/wmem_default)

then lots of packet loss results if I try to send more packets than
the bandwidth of the wire (300 bytes the maximum rate is 341k pps). With a
size of 2M for the output buffer the TX ring is overrun.

But this loss is nowhere seen in any counter increments:

Is there any chance this is getting dropped at qdisc?
Can you check with tc?

thanks,
Nivedita