Re: stmmac ethernet in kernel 4.4: coalescing related pauses?

On 28.11.2016 16:31, Eric Dumazet wrote:

On Mon, 2016-11-28 at 09:54 -0500, David Miller wrote:

quoted

From: Lino Sanfilippo <redacted>
Date: Mon, 28 Nov 2016 14:07:51 +0100

quoted

Calling skb_orphan() in the xmit handler made this issue disappear.

This is not the way to handle this problem.

The solution is to free the SKBs in a timely manner after the
chip has transmitted the frame.

Note that the 'pauses' described by Pavel are also caused by a too small
SO_SNDBUF value on the UDP socket.

An immediate fix, with no kernel change is to increase it.

echo 1000000 >/proc/sys/net/core/wmem_default

or

val = 1000000;
setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &val, sizeof(val));

I wonder if the best fix would be indeed to deactivate irq coalescing completely.
Does it make any sense at all to use it if a driver uses NAPI already?

Regards,
Lino