Re: interface send-q stall in 6.99.40?

[David Young <dyoung%pobox.com@localhost>]

On Mon, May 12, 2014 at 10:39:52PM +0200, Manuel Bouyer wrote:
> On Mon, May 12, 2014 at 09:56:30PM +0200, Frank Kardel wrote:
> > [...]
> > traceroute packets from outside look like the are anwsered, but ICMP ECHO is
> > not answered.
> > 
> > The interface recovers with an ifconfig wmX down/up.
> > 
> > While I do not know how to provoke this on wm (just happens once a week). I
> > found the same phenomenon occurring on a Raspberry Pi when detaching the
> > cable. The same symptoms occur there and ifconfig usmsc0 down/up will
> > recover.
> > 
> > Is anybody else seeing this?
> 
> I do, on a amd64 host with wm interface. Disabling TSO4 and TSO6 fixed the
> problem for me.

I think the problem is that a very large TSO buffer chain won't fit in
the Tx DMA maps that wm(4) allocates. wm(4) will retry the transmission
forever.  TSO needs bigger Tx maps.  At $DAYJOB, looks like we fixed
this bug by increasing WM_MAXTXDMA to 2 * round_page(IP_MAXPACKET).

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981