27 Feb
2017
27 Feb
'17
8:09 p.m.
Ooo. Fun. We're talking PDP-10s on a Unix list... :-)
On 2017-02-27 16:13, Arthur Krewat <krewat(a)kilonet.net> wrote:
In TOPS-10, you could detach from your current job,
login again, and
keep going. Then, attach to the previous job, and go back and forth
endlessly.
Right. But that is a different thing. Each terminal session only have
one job. The fact that you can detach that, and log in as a new session
is a different concept.
As for keeping memory around, it was very common on
TOPS-10 to put code
in a "hiseg" that would stick around, and was shareable between
"jobs".
Yes. Again, that is a different thing as well. Hisegs are more related
to shared memory.
I assume you know all this, so I'm not going to go into details.
But having the memory around for a program, even if it is not running,
is actually sometimes very useful. If ITS could handle that, while
treating them as separate processes, all associated to one terminal, and
let you select which one you were currently fooling around in, while the
others stayed around, that is something I don't think I've seen elsewhere.
For something like EMACS, it would be very efficient
to have the first
person run it "compile" all the LISP, leave it in the hiseg, and other
jobs can then run that code.
That would work, but it would then require that all other users be
suspended until the first user actually completes the initialization,
and after that, all the memory must be readonly.
Not knowing anything about EMACS, I'm not sure
that compiled code was
actually shareable if it was customized, just thinking out loud.
You can certainly customize and save your own image. But the general
bootstrapping of Emacs consists of starting up the core system, and then
loading a whole bunch of modules and configurations. All that loading
and parsing of those files into data structures in memory is quite cpu
intensive.
Once all that processing is finished, you can start editing.
Each person essentially wants all that work done, no matter what they'd
like to do later. So, Emacs does it once, and then saves the state at
the point where you can start editing.
But it does not mean that the memory is shareable. It's full of various
data structures, and code, and that will change as you go along editing
things as well.
But even without leveraging the hiseg capability, it
was relatively easy
to save an entire core image back to a .SAV or .LOW or later a .EXE. I
don't remember how easy it was to do that programmatically, but it was
easy from the terminal and if it saves a lot of processor time (and
elapsed time) people would have been happy to do it manually.
Indeed. Like I said, Tops-10 have the same concept as Emacs does today.
But there it was essentially what you always did.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
27 Feb
27 Feb
8:26 p.m.
New subject: Emacs and undump
Johnny Billquist wrote:
But having the memory around for a program, even if it
is not running,
is actually sometimes very useful. If ITS could handle that, while
treating them as separate processes, all associated to one terminal,
and let you select which one you were currently fooling around in,
while the others stayed around, that is something I don't think I've
seen elsewhere.
And it's not just a list structure, but a tree. You can e.g. start a
new DDT, which itself can have inferior jobs (subprocesses).
To bring this slightly back on topic, ITS job handling was John Kulp's
inspiration for Unix job control. Control-Z does pretty much the same
thing in both ITS and Unix.
So, Emacs does it once, and then saves the state at
the point where
you can start editing. But it does not mean that the memory is
shareable. It's full of various data structures, and code, and that
will change as you go along editing things as well.
Much is sharable. There's a concept of purification (which also comes
from ITS). A purecopy() function is used in temacs to put read-only
data in a special memory area. That area will become sharable in the
dumped Emacs.
9:06 p.m.
New subject: Emacs and undump
On 2017-02-27 21:26, Lars Brinkhoff wrote:
There are definitely some shareable things, but you need to remember
that even some pure, read-only data can be problematic in a shared
segment, as not all people might even have that data loaded, even if the
data itself is readonly.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Johnny Billquist wrote:
Hmm. That sounds similar to TOPS-20 then maybe.
But having the memory around for a program, even
if it is not running,
is actually sometimes very useful. If ITS could handle that, while
treating them as separate processes, all associated to one terminal,
and let you select which one you were currently fooling around in,
while the others stayed around, that is something I don't think I've
seen elsewhere.
And it's not just a list structure, but a tree. You can e.g. start a
new DDT, which itself can have inferior jobs (subprocesses). So, Emacs does
it once, and then saves the state at the point where
you can start editing. But it does not mean that the memory is
shareable. It's full of various data structures, and code, and that
will change as you go along editing things as well.
Much is sharable. There's a concept of purification (which also comes
from ITS). A purecopy() function is used in temacs to put read-only
data in a special memory area. That area will become sharable in the
dumped Emacs.
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