Alan Altmark wrote:
On Sunday, 10/01/2006 at 06:53 AST, David Boyes <[EMAIL PROTECTED]>
wrote:
Thus my suggestion for using PVM. If we really need to solve this
problem, there has to be some packetization going on somewhere to
circumvent the byte-banging-kills-us problem. The PVM line protocol is
relatively efficient, and while it might be a bit jerky, we can pick the
individual characters out of the incoming stream and respond fairly
elegantly w/o constant polling, eg. it would allow presenting a
byte-oriented function w/o making the machine do byte-oriented I/O.
QDIO handles the real live data coming in from the wire, and it doesn't
suffer from the traditional I/O interrupt problems. I also think our
atavistic fear of interrupts is rooted in memories of a distant past when
(a) we had only one CPU, and (2) that CPU was REALLY slow. Today we tout
the mainframe as being best-of-breed for context switching. But what
triggers those context switches? Interrupts, of course. Timers.
But for these quasi-emergency uses of character-at-a-time, I don't think
it matters. You can see it in action today with linemode telnet. Every
character you type at the client is immediately shipped to the host. There
the telnet server lies in wait, watching for the unsuspecting CR. When it
finally arrives, the server sends the accumulated data to CP.
The design challenge is to connect a linemode telnet session to the guest
virtual ASCII console, bypassing the buffering and the
ASCII->EBCDIC->ASCII translation.
Exactly. A telnet (or ssh) session into VM which is then passed byte by
byte to the Linux guest would do what I'm suggesting might be done with
hardware (but only for VM guests, it wouldn't help Linux on the bare metal).
You still need hardware, real or virtual, to cover the case that the
network's down.
--
Cheers
John
-- spambait
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