High rate traffic silence an em interface.

[Shunsuke SHINOMIYA]

 Hi,

 traffic over output interface's transmission rate silence an em
interface with 5.3-BETA5.

 I configured a P4 with HTT box with two em interfaces for a router, one
interface is set to 100BaseTX, the other is set to 10BaseT.

 And I sent the IPv4 11Mbps(only 1Mbps exceed 10Mbps) traffic for 10
seconds from 100BaseTX side to 10BaseT side by smartbits, most of
packets dropped and this measurement terminated with failure.
 Then I did ping to a host over 10baseT side at the box, ping outputted
with "No buffers space avilable".

>> ping 10.1.1.3
>PING 10.1.1.3 (10.1.1.3): 56 data bytes
>ping: sendto: No buffer space available
>^C
>--- 10.1.1.3 ping statistics ---
>1 packets transmitted, 0 packets received, 100% packet loss

 I found two methods for recovery. One is up & down the interface of
10BaseT side, the other (strange?) one is ping6 to the host over 10baseT
side like "ping6 ff02::1%em1".

 "Tx Descriptors not avail1" counter by hw.em1.debug_info increased.
Another counters kept zero.

> em1: Adapter hardware address = 0xc3dc6b34
> em1:CTRL  = 0x40f01849
> em1:RCTL  = 0x8002 PS=(0x8402)
> em1:tx_int_delay = 0, tx_abs_int_delay = 0
> em1:rx_int_delay = 0, rx_abs_int_delay = 0
> em1: fifo workaround = 0, fifo_reset = 0
> em1: hw tdh = 132, hw tdt = 132
> em1: Num Tx descriptors avail = 256
> em1: Tx Descriptors not avail1 = 6430
> em1: Tx Descriptors not avail2 = 0
> em1: Std mbuf failed = 0
> em1: Std mbuf cluster failed = 0
> em1: Driver dropped packets = 0


 Is this a peculiar problem just with me?

-- 
Shunsuke SHINOMIYA <shino at fornext.org>