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

From: Pavel Machek <[email-masked]>
Date: Wed, 30 Nov 2016 11:28:57 +0100

On Mon 2016-11-28 07:31:43, Eric Dumazet wrote:
> On Mon, 2016-11-28 at 09:54 -0500, David Miller wrote:
> > From: Lino Sanfilippo <[email-masked]>
> > Date: Mon, 28 Nov 2016 14:07:51 +0100
> > 
> > > 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

Thanks a lot. For the record, that works around the problem, too. (Or
at least helps a lot; it may be possible that problem still remains if
continuous stream of packets is going to trigger this, if I read the
sources correctly.)

Best regards,
									Pavel
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