Slow transmission with Marvell SKnet

[Frank Wille <frank%phoenix.owl.de@localhost>]

Hi,

I think we have a problem in the sk(4) driver for Marvell Yukon SK-Net.
Probably since ever. But I didn't notice it before I made one of my sk(4)
based Synology NAS into a media server.

I have three NetBSD/sandpoint based NAS with the same sk(4) chip, which
all show transmit rates between 20 Kib/s and 1800 KiB/s during a simple FTP
test, while receiving is always at more than 5000 KiB/s: DS-101g+, DS-209j
and CS-406e:

skc0 at pci0 dev 15 function 0: irq 18
skc0: interrupt moderation is 0 us
skc0: Marvell Yukon Lite Gigabit Ethernet rev. (0x9)
sk0 at skc0 port A: Ethernet address 00:11:32:00:xx:xx
makphy0 at sk0 phy 0: Marvell 88E1011 Gigabit PHY, rev. 5

While the receive-speed is quite constant, the transmit-speed varies a lot,
depending on the machine and NIC on the other end of the FTP connection.
For example I have seen less than 50 KiB/s on a iBook G4 (NetBSD/macppc)
with gem(4), where the rate quickly oscillates between 20 and 200 KiB/s
during the transmission.

There are no errors or collisions, though:

Name  Mtu   Network       Address              Ipkts Ierrs    Opkts Oerrs Colls
sk0   1500  <Link>        00:11:32:00:xx:xx   581303     0   426085     0     0

The interface is configured like this (100MBit, because I have no GBit
ethernet or switches):

sk0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        ec_capabilities=5<VLAN_MTU,JUMBO_MTU>
        ec_enabled=0
        address: 00:11:32:00:xx:xx
        media: Ethernet 100baseTX full-duplex
        status: active
        inet 192.168.41.101 netmask 0xffffff00 broadcast 192.168.41.255

I have a comparable Qnap TS-101 NAS, with the same CPU, RAM and clock, but
with a Realtek NIC. It has no problem transmitting more than 4 MiB/s, to
any client I connect!

Can anybody confirm the problem? Or am I missing something?

-- 
Frank Wille