From: sct@dcs.ed.ac.uk (Stephen Tweedie) Subject: Re: Coherent vs. Linux - a comparo Date: 22 Jun 1993 02:09:46 GMT
On 21 Jun 93 14:29:28 GMT, gah@netcom.com (Gregg Hungerford) said:
> I am a big fan of virtual memory. My point is that I've used it
> with a variety of drives and found anything slower than 8ms isn't
> tolerable for my needs.
I can accept that - no problem. For *my* needs, Linux virtual memory
works brilliantly.
> The problem is that low end systems like that have a tendency to
> thrash. When that happens, you'll find yourself watching the disk
> constantly paging back and forth, tying up the whole system, while
> nothing happens.
I've got a clunky IDE drive, but that's perfectly adequate. I have
16MB of ram, and I rarely need that much *active* memory. Swapping
(or paging) just comes down to writing out to disk data which isn't
used.
Large packages such as emacs and X have significant amounts of data or
code space which are only used during rare operations or at startup,
and VM allows this space to be reclaimed by other apps when it's not
in use. There's a big difference between this kind of memory
management, and trashing; disk speed is really critical if you are
paging heavily, but VM can give big benefits just by swapping out
unused core, for which disk speed is very much less important.
> Again, I'm a fan of virtual memory. I started out in the 70's when
> job swapping was all there was. My point is that I think people have
> some false expectations. On a drive with 3 ms access, virtual memory
> is elegant. On a drive with 15 ms, it's clunky at best.
Not necessarily true. It depends on what you want to use the VM for.
If you are short of physical RAM, most people would probably be better
off getting another 8MB than upgrading to a 3ms disk. As long as you
are not paging heavily, even a 15ms disk is acceptable as swap space
for many purposes.
> Certainly the mips box had more overhead, but I think a system like
> yours would come to a grinding halt trying to run the volume and
> intensity of programs that I was running (including a FULL net news
> feed via uucp).
Fine. That's not a criticism of Linux, is it? Linux works a treat on
a great range of machines. I wouldn't want to try it myself but there
are reports of people running a kernel compile on a 386SX20 with 2 or
3 meg ram, and coming back 24 hours later to find the job done. I've
got a 486DX33 with 16MB ram, and others have 486DX2/66 machines with
32MB ram. Given the extra hardware, Linux can really soar. There
*are* people running FULL net news feeds; not only via dialup uucp,
but over proper internet links.
Point is, you can't sling mud at Linux for not turning a 4MB 386
machine into a network news server. There's no need to say "scrap
Linux, get a *real* machine"; just getting a better PC may be
sufficient, and Linux will cut it as a power OS.
>>>Also, unless you've got a magnifying glass handy, you really need
>>>a good 19" monitor.
>>Hardly. Running my 14" monitor at about 800x600 gives me plenty of
>>room to work, especially with the virtual screen size of 1024x1024 and
>>the virtual screens afforded by my window manager.
> That's a matter of personal taste. I have all sizes of monitors on my
> systems and prefer the less imposing 14" screen. The problem with
> these smaller screens is a matter of clutter. The virtual screen setup
> that comes with coherent is easier for me than searching for and resizing
> windows all the time...
Interesting. I find Linux's virtual consoles to be tremendously
useful, especially as I can mix-and-match text and graphics between
them (even to the extent of running two X servers on separate VCs).
However, for really easy, powerful virtual screen handling under X,
just grab a suitable window manager. I use ctwm - all the time, and I
wonder how I lived without it. It really does make the most of a 14"
screen.
Cheers,
Stephen.