NFSv3 issues with latest -current

[Yuri Pankov]

On Sun, 29 Oct 2017 13:13:31 +0000, Rick Macklem wrote:
> Yuri Pankov wrote:
>> All file operations (e.g. copying the file over NFSv3 for me) seem to be
>> stuck running the latest -current (r325100).  Reverting just the kernel
>> to r323779 (arbitrary chosen) seems to help.  I noticed the "Stale file
>> handle when mounting nfs" message but I don't get the "stale file
>> handle" messages from mount, probably as I'm not running any linux clients.
> These kinds of problems are usually related to your net interface device
> driver or the TCP stack.
> 
> A couple of things to try:
> - Disable TSO (look for a sysctl with "tso" in it).
> - Try using mount options rsize=32768,waize=32768 to reduce the I/O
>    size. Some device drivers don't handle long chains of mbufs well,
>    especially when the size is near 64K.
> (These issues have been fixed in current, but if a bug slips into a net driver
>   update or ???)
> - Look at recent changes to the net device driver you are using and try reverting
>    those changes if you can do so.
> - Capture packets and look at them in wireshark (which knows NFS) and see
>    what is going on the wire.
> 
> There hasn't been any recent changes to NFS that should affect NFSv3 mounts
> or to the kernel rpc, so I doubt the NFSv4.1 changes would be involved.

Thanks for the hints, Rick!

Indeed, it was one of the changes to sys/dev/e1000, reverting just the 
commit made everything look normal again (CC'ing the author).

The NIC is:

igb0 at pci0:2:0:0:        class=0x020000 card=0x10c915d9 chip=0x10c98086 
rev=0x01 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = '82576 Gigabit Network Connection'
     class      = network
     subclass   = ethernet

Interface configuration (note the MTU):

igb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000
options=e525bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
         ether 00:25:90:72:54:22
         inet6 fe80::225:90ff:fe72:5422%igb0 prefixlen 64 scopeid 0x1
         inet 192.168.1.4 netmask 0xffffff00 broadcast 192.168.1.255
         nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
         media: Ethernet autoselect (1000baseT <full-duplex>)
         status: active

And the commit itself:

commit f81cb8df32ae96299b8bbc2e948c17ad3aab59ca
Author: shurd <shurd at FreeBSD.org>
Date:   Sat Sep 23 01:33:20 2017 +0000

     Some small packet performance improvements

     If the packet is smaller than MTU, disable the TSO flags.
     Move TCP header parsing inside the IS_TSO?() test.
     Add a new IFLIB_NEED_ZERO_CSUM flag to indicate the checksums need 
to be zeroed before TX.

     Reviewed by:    sbruno
     Approved by:    sbruno (mentor)
     Sponsored by:   Limelight Networks
     Differential Revision:  https://reviews.freebsd.org/D12442

Notes:
     svn path=/head/; revision=323941