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Re: Multitasking, through Multiple Text Windows

On Sun 06 Jan 2019 at 21:32:10 (-0500), Kenneth Parker wrote:
> Here's more information:
> I gave myself a "text-only" system, via the command:  "systemctl
> set-default multi-user.target"
> Using two Virtual Text consoles:  /dev/tty3 (alt-f3), and /dev/tty4
> (alt-f4).

In view of your earlier comments, who's logged in on them?

> alt-f3 does the command I wish to continue running ("play", but could be
> compiling a Linux Kernel).  alt-f4 gathers information.

By "gathers information", you mean just running ps?

> Music plays fine, when in alt-f3, but stops in alt-f4.

As soon as you switch to VC4, which is already logged in and
sitting at a bash prompt?

> So, I do "ps axu" in alt-f4, to see what happens to the "play" command.
> "Status= "S1+"!

I assume that's Sl+, and if so then that's interesting as ps gives me
9112 8802 1000 tty2 SL+ 0:00 play Videos/2018-summer-music/MP3/band-ellington.mp3

> People say that you don't need a Graphical Environment with a Server.  But
> what if you want to Multitask?

Linux is multitasking whether or not you have a graphical environment.
Just look at the output of ps.

> ****   Test part 2:  on Devuan Ascii.
> First, install it!  (I don't count my Virtualbox version, because it
> doesn't do justice to my Virtual Console tests)
> Now, under Devuan, Music keeps running when I switch Console to alt-f4.
> Now, if I do "ps axu" in alt-f4, I see "Status = SL+"
> So what is the difference between S1+ and SL+?

man ps.

S    interruptible sleep (waiting for an event to complete)
L    has pages locked into memory (for real-time and custom IO)
l    is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+    is in the foreground process group

I don't know the reasons for the difference between my system and
yours, nor whether it's relevant to your problem. Perhaps it depends
on the sound driver: I use alsa but not pulse.

Sox, mpv, mplayer and timidity all lock pages in memory, whereas
audacious doesn't. But audacious carries on playing regardless.