9.2 ixgbe tx queue hang

[Rick Macklem]

Markus Gebert wrote:
> 
> On 26.03.2014, at 00:06, Christopher Forgeron <csforgeron at gmail.com>
> wrote:
> 
> > Update:
> > 
> > I'm changing my mind, and I believe Rick's TSO patch is fixing
> > things
> > (sorry). In looking at my notes, it's possible I had lagg on for
> > those
> > tests.  lagg does seem to negate the TSO patch in my case.
> 
> I’m glad to hear you could check that scenario again. In the other
> email I just sent, I just asked you to redo this test. Now it makes
> perfect sense why you saw oversized packets despite Rick’s
> if_hw_tsomax patch.
> 
> 
> > kernel.10stable_basicTSO_65535/
> > 
> > - IP_MAXPACKET = 65535;
> > - manually forced (no if statement) ifp->if_hw_tsomax =
> > IP_MAXPACKET -
> > (ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN);
> > - Verified on boot via printf that ifp->if_hw_tsomax = 65517
> 
> Is 65517 correct? With Ricks patch, I get this:
> 
> dev.ix.0.hw_tsomax: 65518
> 
> Also the dtrace command you used excludes 65518...
> 
I am using 32 * MCLBYTES - (ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN) which
is 65518. Although IP_MAXPACKET (maximum IP len, not including ethernet header)
is 65535 (largest # that fits in 16bits), the maximum data length
(including ethernet header) that will fit in 32 mbuf clusters is 65536.
(In practice 65517 or anything <= 65518 should fix the problem.)

rick

> > - Boot in a NON LAGG environment.  ix0 only.
> > 
> > ixgbe's printf is showing packets up to 65530. Haven't run long
> > enough yet
> > to see if anything will go over 65535
> > 
With the ethernet header length, it can be <= 65536, because that
is 32 * MCLBYTES.

rick

> > I have this tcpdump running to check packet size.
> > tcpdump -ennvvXS -i ix0 greater 65518
> > 
> > I do expect to get packets over 65518, but I was just curious to
> > see if any
> > of them would go over 65535. Time will tell.
> > 
> > In a separate test, If I enable lagg, we have LOTS of oversized
> > packet
> > problems. It looks like tsomax is definitely not making it through
> > in
> > if_lagg.c - Any recommendations there? I will eventually need lagg,
> > as I'm
> > sure will others.
> 
> I think somebody has to invent a way to propagate if_hw_maxtso to
> interfaces on top of each other.
> 
> 
> > With dtrace, it's showing t_tsomax >= 65518. Shouldn't that not be
> > happening?
> 
> Looks like these all come from bce interfaces (bce_intr in the stack
> trace), which probably have another value for if_hw_tsomax.
> 
> 
> Markus
> 
> 
> > dtrace -n 'fbt::tcp_output:entry / args[0]->t_tsomax != 0 &&
> > args[0]->t_tsomax >= 65518 / { printf("unexpected tp->t_tsomax:
> > %i\n",
> > args[0]->t_tsomax); stack(); }'
> > 
> > 
> >  6  31403                 tcp_output:entry unexpected tp->t_tsomax:
> >  65535
> > 
> >              kernel`tcp_do_segment+0x2c99
> >              kernel`tcp_input+0x11a2
> >              kernel`ip_input+0xa2
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`ether_demux+0x12a
> >              kernel`ether_nh_input+0x35f
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`bce_intr+0x765
> >              kernel`intr_event_execute_handlers+0xab
> >              kernel`ithread_loop+0x96
> >              kernel`fork_exit+0x9a
> >              kernel`0xffffffff80c75b2e
> > 
> >  3  31403                 tcp_output:entry unexpected tp->t_tsomax:
> >  65535
> > 
> >              kernel`tcp_do_segment+0x2c99
> >              kernel`tcp_input+0x11a2
> >              kernel`ip_input+0xa2
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`ether_demux+0x12a
> >              kernel`ether_nh_input+0x35f
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`bce_intr+0x765
> >              kernel`intr_event_execute_handlers+0xab
> >              kernel`ithread_loop+0x96
> >              kernel`fork_exit+0x9a
> >              kernel`0xffffffff80c75b2e
> > 
> >  6  31403                 tcp_output:entry unexpected tp->t_tsomax:
> >  65535
> > 
> >              kernel`tcp_do_segment+0x2c99
> >              kernel`tcp_input+0x11a2
> >              kernel`ip_input+0xa2
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`ether_demux+0x12a
> >              kernel`ether_nh_input+0x35f
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`bce_intr+0x765
> >              kernel`intr_event_execute_handlers+0xab
> >              kernel`ithread_loop+0x96
> >              kernel`fork_exit+0x9a
> >              kernel`0xffffffff80c75b2e
> > 
> >  1  31403                 tcp_output:entry unexpected tp->t_tsomax:
> >  65535
> > 
> >              kernel`tcp_do_segment+0x2c99
> >              kernel`tcp_input+0x11a2
> >              kernel`ip_input+0xa2
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`ether_demux+0x12a
> >              kernel`ether_nh_input+0x35f
> >              kernel`netisr_dispatch_src+0x5e
> >              kernel`bce_intr+0x765
> >              kernel`intr_event_execute_handlers+0xab
> >              kernel`ithread_loop+0x96
> >              kernel`fork_exit+0x9a
> >              kernel`0xffffffff80c75b2e
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