[CentOS] Ethernet poor performance
warren at etr-usa.com
Wed Jul 2 17:14:43 UTC 2008
Robert Moskowitz wrote:
> I get pings around 60ms.
Pings within the same LAN? If so, that's slow even for 100BaseT. It
should be under 10 ms.
> When I switch the cards around, the addon card attached to my
> network, I get pings that alternate with one being ~1488ms and the
> next 488ms! This is regular.
Have you removed the cabling from consideration? And, do you know you
have good cabling, tested as following the wiring standards? Hand-made
cables are particularly suspect, if made by someone who doesn't know
what TIA/EIA 568 is, for example.
> I have played around with the IRQ for the 2nd card. The 1st card I
> tried I was limited to 9,10, or 11. The card I am using now allows
> 3, 4, or 7 (btw, I have disabled serial and parallel ports).
None of this should matter in the PCI world, unless you're using really
old hardware, which didn't properly support IRQ sharing.
>> - What driver is it using?
> How do I tell?
grep eth0 /etc/modprobe.conf
or scan through the output of the dmesg command, looking for stuff that
appears near "eth0".
>> - Can you verify that the speed and duplex settings match on both ends of
>> the connection?
> The switch has its 100Mb LED on. One of the switch ports has my
> Speedstream router which is only 10Mb, so we can believe the 100Mb LED.
> This is a dumb switch (my public network, so I am not going to plug into
> one of my Procurves).
That covers speed, but doesn't say anything about the duplex setting.
You should see this mentioned near the Ethernet driver load lines in
> ho, ho. MTU of 1500. Is this not doing MTU path discovery?
PMTU-D is done per-connection at the TCP layer, not statically down at L2.
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