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As has been discussed, what we call X, is actually
a convergence of various components: X server, Window Manager, Desktop, etc.
With MS Windows, the GUI desktop is tightly integrated with the operating
system itself. This is not the case in Linux which follows the Unix tradition
of combining various independent components to achieve some end result. So we
have choices with each component and it's attendant configuration and
implementation. In short, much flexibility. This is where you come in. You
can try various possibilities and decide what you gives you the most bang for
the buck.
On low end hardware, this gives us much latitude to decrease the demand on
available system resources. This is good because, if given the opportunity,
X can be quite greedy with system resources. If
you've recently installed a new Linux distribution, you've probably been
given a default Desktop with many bells and whistles. And something
that will probably need a fair amount of memory and CPU to achieve a
reasonable level of performance. If you have the horse power, this should not
be a problem.
It is often said that Linux functions very well with relatively little
memory. This is true to a point. It does not mean though that every possible
configuration will run with low memory. So if you want to use memory hungry
applications, then you will have to have the memory. Or you will have to make
sacrifices to achieve a satisfactory level of performance. It is quite
possible to run X with reasonable performance on
16 Meg of RAM, and even less if you really want to push it. But you would
have to live with some real limitations.
Let's look at some of the components and ways to decrease the demand on
system resources, in case you are at the low end on hardware, or performance
is not up to expectations. No big surprise, but overall system performance will be best with a fast
graphics card, a fast hard drive, and lots and lots of memory -- if you want
both a fast and flashy system.
Graphics cards are of course necessary, and the X server's video performance
is tied to the card's chipset, and the corresponding XFree86 driver. Just
because a given card is supported by XFree86 does not necessarily mean it is
as well optimized as other cards! It may also perform better at a lower color
depth (see below). It may well be worth the trip to xfree86.org to see if
there are any notes related to your card with respect to performance or other
issues.
And you might try other versions of XFree86. At this time v4.2 was just
recently released. Some cards may still perform better with 3.3.6 due to the
way v4.x is being incrementally developed. If you are using x4.x and
performance is not good, then make sure you are using the latest available
version.
The more memory, the better. X will do a lot
caching to help performance. But caching requires memory, and if there isn't
much to start with, then we would need to reduce memory requirements. Some
tips for those with low memory or performance problems: Use the free command to make sure all memory and swap is
recognized.
Make sure you don't have other system services that are hogging memory or
CPU. Use top or ps to see what is
running, and disable anything you can to free up memory and CPU. Again, a
default installation may have many things running that you don't really
need.
Make sure you have plenty of swap space. With low, or even modest, memory,
swap is all the more important. A general rule of thumb is twice as much swap
as physical memory. With low memory, this is not enough. Try four times real
memory. Or more. If you can't create more swap partitions, see the
mkswap man page about creating swap files instead.
Constant disk churning is a symptom of insufficient swap space, and the
system will be slowed as a result, sometimes drastically. Or, possibly this
may be the symptom of a poorly behaved kernel VM system (try another kernel
in this case).
Drive performance is important for swap performance. Make sure your drive has
DMA enabled if the drive supports it, and is otherwise tuned and performing
up to snuff. See the hdparm man page. Slow drive + slow
card + low memory = slow system.
Don't use KDE or GNOME
if memory is tight. These both require substantial memory, and are not
required to just run X. Think of these as
usability enhancements. 32M probably may not be enough. 64M may be decent,
depending on what other applications are being used, and other variables. 128M
should be adequate in most situations. 256M or more to
be comfortable. File Managers like Nautilus and
gmc can also be memory hungry.
Use a lightweight window manger. WindowMaker,
BlackBox, IceWM,
fvwm (and variants),
XFce, all have reputations of performing well with
low memory. There are surely others as well. Experiment.
fvwm is generally considered the lightest of the
light. A very nice desktop is still very possible even without
KDE or GNOME. In fact,
most KDE and GNOME
applications can still be used even if KDE and
GNOME are not running themselves (assuming the
right libs are installed).
Don't use fancy themes or backgrounds. Plain and simple is easier on
resources. Use a solid color background. Avoid pixmaps or gradients for any
kind of background, including menus, title bars, etc.
Use a lesser screen size and color depth. 800x600x16 will not push
X as hard and be easier on system resources than
higher values. While a ColorDepth of 24 is preferred, you probably will not
notice the difference of 16 with the majority of applications.
Some applications require much more memory than others. Some notable hogs are
Netscape, Mozilla, office suites, and
the Gimp. Netscape is faster than
Mozilla (but not as nice).
Netscape-Navigator uses less memory than
Netscape-Communicator. Close any of these apps when not in
use. Use text browsers like lynx or w3m
wherever you can, like reading locally installed HTML documentation. Much
faster, and much less memory is required.
Also, use text based clients for mail (mutt or
pine) and news (slrn or
trn). Again, faster and much less memory is used,
and these are after all text based protocols at heart anyway.
rxvt uses less memory than xterm,
konsole or gnome-terminal.
If you run an X session for long periods of time
(like days or weeks), restart X occasionally to
free memory tied up as cache.
Disable "backing store" and "save-unders" to
reduce memory usage (performance penalty though). Check
your Window Manager's settings too. See what modules are being loaded
in the "Modules" section of XF86Config as
well. Your installation may have many unnecessary ones enabled, or ones you
can't take advantage of (e.g. "v4l", aka
"Video4Linux").
Font servers may provide a slight performance boost by off-loading font
rendering to the font server, while freeing the X server to do other things.
But, the font server will use a small additional amount of memory as well.
So, you can try it either way to see if it makes a difference.
Lastly, RAM is cheap now. Buy some ;-) A new drive too.
RAM is still just too low for X? Check out
tinyX:
http://www.superant.com/smalllinux/tinyX01.html.
Reportedly runs in as little as 4 Meg of RAM.
X is not particularly network friendly. In other words, it is a bandwidth
hog. This should not be a problem in LAN situations, but may be if trying to
use X over the Internet. lbxproxy, the low bandwidth X proxy, utilizes
various optimizations to improve performance in low bandwidth, or
high latency situations. See the man page.
VNC (Virtual Network Computing), has some of the same advantages as
X for displaying applications on remote systems, but is more network
friendly. Your Linux installation should have both VNC client and server
packages available.
Other tips to eek out better performance: Use xset to speed up the keyboard. This can make the
system feel more responsive even if it isn't really. The default always
seemed sluggish to me.
renice X to give it a higher
priority. Other platforms give the GUI high scheduling priority to achieve
better responsiveness. But this is at a cost to other processes. Linux is a
blank slate. You might include the font server (if being used), and key
KDE and GNOME processes
as well. This won't do much on systems that are mostly idle.
This does not work so well with startx since
X runs as root, and you're not root, right? So
you'd have to use something like sudo to have this done
automatically.
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Fedora Core 4 Tutorial
