Poor performance with pcnet32 on SMP

Mel Gorman (mel@csn.ul.ie)
Thu, 20 Mar 2003 23:54:21 +0000 (GMT)

I have being noticing some seriously poor network performance with SMP
enabled. The machine is a xSeries 350 with quad xeon procesors. Under UP,
I get decent transfer rates but with SMP enabled, it won't get over 2kB/s.
I tried binding interrupts to one processor with

echo 1 > /proc/irq/16/smp_affinity

which, according to mail archives fixed the problem for other people, but
the result is the same. A CVS checkout from a server on the local lan of a
source tree less than 1MB took over an hour to complete but under UP
completes in about 2 seconds. This occurs with both 2.4.20 and 2.5.64.

In case it is relevant, the dmesg output related to the card on 2.5.64 is

pcnet32.c:v1.27b 01.10.2002 tsbogend@alpha.franken.de
pcnet32: PCnet/FAST III 79C975 at 0x2200, 00 02 55 fc 6d 21 assigned IRQ 16.
eth0: registered as PCnet/FAST III 79C975
pcnet32: 1 cards_found.
eth0: link up, 10Mbps, half-duplex, lpa 0x0021
Module pcnet32 cannot be unloaded due to unsafe usage in include/linux/module.h:457

Any suggestions on how to fix this are appreciated

-- 
Mel Gorman
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