jumbograms (& em) & nfs a no go

[Doug Ambrisko]

Michal Mertl writes:
| On Thu, 30 Oct 2003, Sam Leffler wrote:
| 
| > On Thursday 30 October 2003 04:46 am, Michal Mertl wrote:
| > > I wanted to test gigabit network performance and found out that current
| > > (from 5.0 to up to date -current) doesn't fully work with jumbograms (MTU
| > > set to 6000), Intel adapters and nfs (both UDP and TCP).
| > >
| > > I checked that the same thing works with 4.9.
| > >
| > > I then left one computer at 4.9 and upgraded the other to 5.0. When I
| > > mount a partition from 5.0 machine I found out, that copying reliably
| > > works only from 5.0 to 4.9. The other way around I see messages 'em0:
| > > discard oversize frame (ether type 800 flags 3 len 67582 > max 6014)' on
| > > 5.0 and the copying stalls. On 4.9 machine I later see 'nfs server
| > > 10.0.0.2:/usr: not responding'. The interface is stuck for some time - can
| > > be revived by changing mtu back to 1500 and down/up sequence.
| >
| > I've ran many jumbogram tests of machines connected with a cross-over cable
| > and em devices at each end.  If you've got a swtch in the middle make sure it
| > does the right thing.
| 
| I also used exclusively crossover cable. The same configuration worked
| with 4.9. The problem appears only with NFS.

You might want to try this patch:

Index: if_em.c
===================================================================
RCS file: /cvs/src/sys/dev/em/if_em.c,v
retrieving revision 1.32
diff -c -r1.32 if_em.c
*** if_em.c	15 Oct 2003 05:34:41 -0000	1.32
--- if_em.c	30 Oct 2003 19:39:49 -0000
***************
*** 2454,2460 ****
                                 BUS_SPACE_MAXADDR,       /* highaddr */
                                 NULL, NULL,              /* filter, filterarg */
                                 MCLBYTES,                /* maxsize */
!                                1,                       /* nsegments */
                                 MCLBYTES,                /* maxsegsize */
                                 BUS_DMA_ALLOCNOW,        /* flags */
  			       NULL,			/* lockfunc */
--- 2454,2460 ----
                                 BUS_SPACE_MAXADDR,       /* highaddr */
                                 NULL, NULL,              /* filter, filterarg */
                                 MCLBYTES,                /* maxsize */
!                                2,                       /* nsegments */
                                 MCLBYTES,                /* maxsegsize */
                                 BUS_DMA_ALLOCNOW,        /* flags */
  			       NULL,			/* lockfunc */

There was a few bugs in the system before in that there was insufficient
error check in the bus_dma stuff.  The issue was that HW was writing more
then was the allocated due to (nsegments=1).  This isn't the right fix but
might help point to the issue.

I don't have access to the HW to test it out anymore.

Doug A.