[PATCH-2.4] forcedeth update to 0.50

[Willy Tarreau]

 Hi Manfred,

Today I had an opportunity to perform some functional and performance
tests on a SunFire X2100, which is a PCI Express-based Dual Core Opteron 
equipped with a broadcom gigabit LAN chip (tg3) and an Nforce4 Pro
chipset offering a second LAN port (forcedeth).

With the forcedeth driver version 0.30 as shipped in 2.4.33-pre*, ping
was OK, but the driver hanged after a few megabytes of Gigabit-speed
outgoing traffic, with some "NETDEV transmit time out" messages. It was
necessary to unload then reload it. So I decided it was time to give
your updates a try.

I started from the latest backport you sent in september (0.42) and
incrementally applied 2.6 updates. I stopped at 0.50 which provides
VLAN support, because after this one, there are some 2.4-incompatible
changes (64bit consistent memory allocation for rings, and MSI/MSIX
support).

It compiled and worked immediately, and now shows very high performance !
Right now, there's a test running at 925 Mbps and 400 kpps, but I could
reach 1.09 Mpps of input traffic and full gigabit speed above 400 bytes
per packet without any trouble. The test above has been running for 6
hours now, which represents 2.5 TB and 8.6 billions of packets. Moreover,
the test only consumes 15% CPU after I set the poll_interval limit to 10
microseconds.

However, I had to increase the max_interrupt_work to 10, because at 5,
I would receive the following message almost every second (both in 0.30
and 0.50) : "too many iterations (6) in nv_nic_irq". At 10, it never
happened.

I guess we should raise it both in 2.4 and 2.6, but I did not do it in
the patch below because I wanted the code to be as similar as possible
between the two trees.

Given that the driver is almost not usable in 0.30, I suspect that very
few people currently use it as-is with kernel 2.4. And since it shows
excellent performance in 0.50, and does not exhibit any instability, I
think that there would be far more benefits than risks in merging it.

How do you feel about this ?

BTW, I have CCed John Linville who maintains network drivers for RHEL3
and who might be interested too.

Regard,
Willy