"Different" interactive performance.

From: Richard B. Johnson (root@chaos.analogic.com)
Date: Fri Feb 04 2000 - 09:29:47 EST


Linux 2.3.41 seems to have a new characteristic which makes interactive
performance poor.

A telnet session with a host in my office, connected through a private
hub, shows a noticeable delay in character echo when interacting with
the host.

Executing `vi` shows the delay to be so bad that escape-sequences
time-out if, for instance it's in `insert` mode, and I use the arrow
keys.

Benchmarks of streaming data look fine. It's the character I/O that
has suffered miserably. I haven't got the time (need a work-break)
to check tcpdump's output, but perhaps somebody else can experiment
and see what's going on.

A preminary check seems to indicate that the network is okay. It looks
as though there has been some kind of delay added when using virtual
terminals (perhaps buffering has changed). I guess this because
telnet to the echo port shows no visible delay. It's only when an
interactive session is established, which use virtual terminals, that
the delay becomes obvious.

Cheers,
Dick Johnson

Penguin : Linux version 2.3.41 on an i686 machine (800.63 BogoMips).

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