Re: [ALACPP] Off-Topic: Weird bandwidth on linux machine

[Christopher Smith <x@xxxxxxxx>]

On Fri, 2003-08-15 at 10:25, Jon Stewart wrote:
> Not having IPerf handy, I decided to use ftp for benchmarking. Here's what 
> I discovered this morning:
> 
> 			To/Recipient
> From/Sender	iMac		Linux		Win2k
> iMac		--		6.6 KB/s	6.0 MB/s
> Linux		6.0 MB/s	--		6.0 MB/s
> Win2k		6.0 MB/s	64 KB/s		--

Well, tcpdump for this stuff would undoubtedly prove enlightening. A
couple of thoughts as to possible issues that may be effecting this
(from least likely to most likely, because I like the suspense):

1) TCP features on the Linux box: Weird MTU sizes, receive buffer sizes,
of disabling large window sizes. Of course, most of this stuff would
likely have an effect on send performance.
 
2) Bad cabling. I'd believe this but for the fact that Linux appears to
have good send performance. Admittedly, some kind of a screw up on the
receive cabling could cause this.

3) Bad adapter: You should track errors and overruns on the Linux
adapter (ifconfig will give you stats on these). Try using a different
adapter.

4) Bad driver: What driver are you using? Not all Linux drivers were
created equal. It's almost like the driver isn't clearing the receive
buffer nearly often enough.

5) The adapter is having some kind of an autodetect problem. This is the
most likely cause of your nightmare. There is a good utility out there
called mii-diag (there is a seperate one for 3com cards) which will get
the "real" state of your card (there are several Linux drivers which get
this wrong, mostly because Linux tries to use the same driver for a ton
of different cards) and more importantly let you force a particular
setting. It is still a tad odd that you'd get good send performance, but
who knows.

Let me know what you are getting.

-- 
Christopher Smith <x@xxxxxxxx>
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