[RndTbl] Network performance tuning

Trevor Cordes trevor at tecnopolis.ca
Thu Apr 15 02:14:51 CDT 2010

On 2010-04-14 Kevin McGregor wrote:
> And finally (I'm kinda done messing around with this): I took out all
> other cards save for the AGP video card and re-ran iperf, and got 162
> Mb/s with the XP PC sending to the Linux server and 612 Mb/s sending
> from the server to the PC. Unpleasantly asymmetric.

Finally had a mo to test my systems, which have similar problems.

my comps:
pog   : Fedora 12, Core2Q, PRO/1000 MT Server NIC
piles : Fedora 10, PD 3G , PRO/1000 MT Server NIC
peecee: XP, Core i7, PRO/1000 PT Desktop NIC (PCIe)
switch: Linksys WebSmart SRW2016, jumbo OFF

All NICs have as much offloading turned on as possible.

iperf results in order of slow to fast:

-s	-t
piles   peecee  300
pog     peecee  351
peecee  pog     400
peecee  piles   401
piles	pog     743
pog	piles	744

Now, I can't seem to figure out whether it's the -s that's sending or
the -t, so I just list as above.  Very consistent results with anything
involving the PC (my fastest hardware!) being much slower than I get
linux->linux.  Sure, the peecee has a "lesser" NIC, but it's still an
expensive one.

The above results mirror what I see in daily life going from piles
(file server) to peecee using samba (the only thing I care about from

When I have another mo, I'll boot a live linux CD and test peecee with
that to see if it's the hw to blame or simply XP.  I've seen lots of
reports about XP having braindead TCP and regedit tweaks to make it
faster.  I've tried many of them with little success.

If anyone wants to also guess as to why my network speed about doubles
when I turn OFF jumbo packets(!!!), please be my guest!  (Yes, I'm
pretty sure I had jumbos configured properly on all NICs/switch, etc.)

> I'll wait a bit to see if any new AMD CPUs are coming out, and then
> buy a quad- or hex-core CPU/motherboard/RAM and hope for a decent
> network interface.

Or buy a nice NIC now :-)  The onboard NICs are usually always
substandard and often crippled (no jumbo, etc).

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