SGI Developer Toolbox 6.1/SGI Developer Toolbox 6.1 - Disc 4.iso/FAQs/netfaqs/X.speedups-faq

Text File | 1994-08-01 | 33KB | 757 lines

Newsgroups: comp.windows.x,news.answers,comp.answers
From: [e-mail] (Art Mulder)
Subject: comp.windows.x: Getting more performance out of X.  FAQ
Followup-To: poster
Date: 15 Apr 1994 14:39:48 GMT
Organization: Computing Science, U of Alberta, Edmonton, Canada
Lines: 741
Approved: [e-mail]
Expires: 20 May 94 23:00:00 GMT
Reply-To: [e-mail] (Art Mulder)
Summary: This posting contains a list of suggestions about what you can do to get the best performance out of X on your workstation -- without buying more hardware.
Keywords: FAQ speed X
Xref: bloom-beacon.mit.edu comp.windows.x:23711 news.answers:18078 comp.answers:4917

Archive-name: x-faq/speedups
Last-modified: 1994/03/10

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    HOW TO MAXIMIZE THE PERFORMANCE OF X -- monthly posting
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
        Compiled by Art Mulder ([e-mail])

  More RAM, Faster CPU's, More disk space, Faster Ethernet....  These
  are the standard responses you hear when you ask how to improve the
  performance of your workstation.

  Well, more hardware isn't always an option, and I wonder if more
  hardware is always even a necessity.

  This "FAQ" list is a collection of suggestions and ideas from different
  people on the net on how you can the best possible performance from X
  Windows on your workstation, WITHOUT PURCHASING MORE HARDWARE.

  Performance is a highly subjective issue.  The individual user must
  balance `speed' versus `features' in order to come to a personal
  decision.  Therefore this document can be be expected to contain many
  subjective opinions in and amongst the objective facts.

  This document is specifically concerned with X.  There are of course
  many other factors that can affect the performance of a workstation.
  However, they are outside the scope of this document.

    [ People seriously interested in the whole area of system
    performance, might want to look at the O'Reilly Nutshell Handbook
    "System Performance Tuning" by Mike Loukides.  IMHO, it contains a
    well-written, comprehensive treatment of system performance.  I
    refer to it a lot.  I'm unaware of any other similar books.  --ed.]

-----------------
Table of Contents
-----------------
  0. Introduction & Administrivia
  1. Window Managers
  2. The X Server
       Which Server?
       Locking the Server into RAM?
       Starting your Server
       Fonts
       About the Resources File
       Define Your Display Properly
  3. Clients
       A Better Clock for X
       A Better Terminal Emulator for X
       Other Client Comments
       Tuning your client
  4. Miscellaneous Suggestions
       Pretty Pictures
       A Quicker Mouse
       Programming Thoughts
       Say What!?
  5. Other Sources of Information
       The "Other X FAQ"
       Books & etc.
  6. Author & Notes

! = changed since last issue.
* = new since last issue.

-----------------------------
Introduction & Administrivia
-----------------------------

  This document is posted each month, on or around the 15th, to the
  Usenet news groups comp.windows.x, news.answers, and comp.answers.
  If you are reading a copy of this FAQ which is more than a few
  months old (see the "Last-modified" date above) you should probably
  locate the latest edition, since the information may be outdated.

  If you do not know how to get those newsgroups and/or your site does
  not receive them and/or this article has already expired, you can
  retrieve this FAQ from an archive site.

  There exist several usenet FAQ archive sites.  To find out more about
  them and how to access them, please see the "Introduction to the
  news.answers newsgroup" posting in news.answers.

  The main FAQ archive is at rtfm.mit.edu.  This document can be found
  there in /pub/usenet/news.answers/x-faq/speedups.  If you do not have
  access to anonymous ftp, you can retrieve it by sending a mail
  message to [e-mail] with the command "send
  usenet/news.answers/x-faq/speedups" in the message body.

---------------
Window Managers
---------------

  There are a lot of window managers out there, with lots of different
  features and abilities.  The choice of which to use is by necessity a
  balancing act between performance and useful features.  At this
  point, most respondents have agreed upon "twm" as the best candidate
  for a speedy window manager.

  A couple of generic tricks you can try to soup up your window manger,
  is turning off unnecessary things like "zooming" and "opaque move".
  Also, if you lay out your windows in a tiled manner, you reduce the
  amount of cpu power spent in raising and lowering overlapping
  windows.                           Joe English ([e-mail])

  I've found that a good font for tiling is 7x13 (aka:
  -misc-fixed-medium-r-normal--13-100-100-100-c-70-iso8859-1 ). It is
  the biggest font I know of that I can use on my Sun (1152x900 screen)
  and still get two 80 column terminal windows side-by-side on the
  display with no overlap.  Other font suggestions will be accepted.

Suggestions for your consideration:

  Linux'ers and others might want a look at fvwm.  A light-weight
  virtual wm, targeted at ``machines with too little memory, at laptops
  on which mouse usage may be awkward, and at users who prefer the
  appearance of the Motif window manager to twm ... all wm functions
  can be performed w/out a mouse'' [from the README].
                                   Zack Evans ([e-mail])

  While originally developed for Linux, fvwm will compile on a number
  of different platforms.  The fvwm docs claim a memory consumption of
  about 1/3 to 2/3 that of twm.

  Speaking personally, fvwm may consume less memory but I found that it
  `feels' slower than twm.  (For example: grab a window - I use opaque
  move - and drag it around the screen.  Twm has a very snappy
  response, but with fvwm v1.05 the window was lagging way behind the
  pointer.  This comparison was done on two identical Sun SLC's)
  However, I will also grant that fvwm is a young piece of software
  that is being rapidly updated & improved so these concerns may soon
  be fixed.                                                      [ed]

------------
The X Server
------------

Which Server?
- - - - - - -
  Make sure that your server is a proper match for your hardware.
  If you have a monochrome monitor, use a monochrome X11 server.

  On my Monochrome Sun, I haven't noticed much difference between
  the Xsun (colour) server and XsunMono, however it was pointed out to
  me that XsunMono is about 800k smaller and therefore should contribute
  to less paging.
         [ thanks to: Jonny Farringdon ([e-mail]),
                        Michael Salmon ([e-mail]) ]

  How your server was compiled can also make a difference.  Jeff Law
  ([e-mail]) advises us that on a Sun system, X should be
  compiled with gcc (version 2.*) or with the unbundled Sun compiler.
  You can expect to get "*very* large speedups in the server" by not
  using the bundled SunOS compiler.  I assume that similar results
  would occur if you used one of the other high-quality commercial
  compilers on the market.

Locking the Server into RAM?
- - - - - - - - - - - - - - -
  It was suggested that perhaps hacking the X server so that it would
  stay locked in RAM (and therefore not get paged out) might help
  performances.  eg: via a call to plock().
       [Eric C Claeys ([e-mail]), Danny Backx ([e-mail]),
    Juan D. Martin ([e-mail])]

  Kenny Ranerup [[e-mail]] tried this a few years ago and
  confirmed that it does work, and can give a noticeable speedup.  But,
  you must be careful that your server doesn't grow too large (ie,
  close to the size of your RAM).  He also makes the point that slow
rformace is in many cases due to client paging (paging
  in libraries), and not server paging.

Starting your Server
- - - - - - - - - - -
  Joe English ([e-mail]) :
    If you start up a lot of clients in your .xsession or whatever, sleep
    for a second or two after launching each one.  After I changed my
    .xclients script to do this, logging in actually took *less* time...
    we have a heavily loaded system without much core, though.

  This sounds crazy, but I have confirmed that it works!

  Warner Losh ([e-mail]) provided me with a good
  explanation of why this works, which I have summarized here:

    When you start up an X server it takes a huge amount of time to
    start accepting connections.  A lot of initialization is done by
    the server when it starts.  This process touches a large number of
    pages.  Any other process running at the same time would fight the
    server for use of the CPU, and more importantly, memory.  If you
    put a sleep in there, you give the Server a chance to get itself
    sorted out before the clients start up.

    Similarly, there is also a lot of initialization whenever an X
    client program starts: toolkits registering widgets, resources
    being fetched, programs initializing state and "databases" and so
    forth.  All this activity is typically memory intensive.  Once this
    initialization is done ("The process has reached a steady state"),
    the memory usage typically settles down to using only a few pages.
    By using sleeps to stagger the launching of your clients in your
    .Xinitrc , you avoid them fighting each other for your
    workstation's limited resources

  This is most definitely a "Your Mileage May Vary" situation, as there
  are so many variables to be considered: available RAM, local swap
  space, load average, number of users on your system, which clients
  you are starting, etc.

  Currently in my .xinitrc I have a situation like:
    (sleep 1; exec xclock ) &
    (sleep 1; exec xbiff ) &
    (sleep 1; exec xterm ) &
    (sleep 1; exec xterm ) &

  I've experimented with:
    (sleep 1; exec xclock ) &
    (sleep 2; exec xbiff ) &
    (sleep 3; exec xterm ) &
    (sleep 4; exec xterm ) &

  I've even tried:
    (sleep 2; exec start_X_clients_script ) &
  and then in start_X_clients_script I had:
    (sleep 1; exec xclock ) &
    (sleep 1; exec xbiff ) &
    (sleep 1; exec xterm ) &
    (sleep 1; exec xterm ) &

    [ The idea with this last one was to make sure that xinit had
    completely finished processing my .xinitrc, and had settled down
    into a "steady state" before the sleep expired and all my clients
    were launched. ]

  All of these yielded fairly comparable results, and so I just stuck with
  my current setup, for its simplicity.  You will probably have to
  experiment a bit to find a setup which suits you.

Fonts
- - -
  Loading fonts takes time and RAM.  If you minimize the number of fonts
  your applications use, you'll get speed increases in load-up time.

  One simple strategy is to choose a small number of fonts (one small, one
  large, one roman, whatever suits you) and configure all your clients -- or
  at least all your heavily used clients -- to use only those few fonts.
  Client programs should start up quicker if their font is already loaded
  into the server.  This will also conserve server resources, since fewer
  fonts will be loaded by the server.
                  [ Farrell McKay ([e-mail]),
                    Joe English ([e-mail]) ]

  eg: My main xterm font is 7x13, so I also have twm set up to use 7x13
  in all it's menus and icons etc.  Twm's default font is 8x13.  Since
  I don't normally use 8x13, I've eliminated one font from my server.

  Oliver Jones ([e-mail]):
    Keep fonts local to the workstation, rather than loading them over nfs.
    If you will make extensive use of R5 scalable fonts, use a font server.

About the Resources File
- - - - - - - - - - - - -

    Keep your .Xresources / .Xdefaults file small.  Saves RAM and saves
    on server startup time.          Joe English ([e-mail])

  One suggestion:

    In your .Xresources file, try putting only the minimum number of
    resources that you want to have available to all of your
    applications.  For example:  *reverseVideo: true

    Then, separate your resources into individual client-specific
    resource files.  For example: $HOME/lib/app-defaults.  In your
    .login file set the environment variable XUSERFILESEARCHPATH:

    setenv XUSERFILESEARCHPATH $HOME/lib/app-defaults/%N

    (Note:  It is easier and quicker for Xt to process
    XUSERFILESEARCHPATH than XAPPLRESDIR.)

    [ The "comp.windows.x Frequently Asked Questions" FAQ contains
    an excellent explanation of how this and the other main X
    environment variables work.  --ed.]

    So, when xterm launches, it loads its resources from
    .../app-defaults/XTerm.  Xdvi finds them in .../app-defaults/XDvi,
    and so on and so forth.  Note that not all clients follow the same
    XXxxx resource-file naming pattern.  You can check in your system
    app-defaults directory (often: /usr/X11R5/lib/X11/app-defaults/) to
    find the proper name, and then name your personal resource files
    with the same name.

    This is all documented in the Xt Specification (pg 125 & 666).
            [Thanks to: Kevin Samborn ([e-mail]),
                 Michael Urban ([e-mail]),
             Tom Bagli ([e-mail]),
                     and Mike Long ([e-mail]).
         Kevin is willing mail his setup files to inquirers.]

  This method of organizing your personal resources has the following
  benefits:

    - Easier to maintain / more usable.

    - Fewer resources are stored in the X server in the RESOURCE_MANAGER
      property.  As a side benefit your server may start fractionally
      quicker, since it doesn`t have to load all your resources.

    - Applications only process their own resources, never have to sort
      through all of your resources to find the ones that affect them.

  It also has drawbacks:

    - the application that you are interested in has to load an
      additional file every time it starts up.  This doesn't seem to
      make that much of a performance difference, and you might
      consider this a huge boon to usability.  If you are modifying an
      application's resource database, you just need to re-run the
      application without having to "xrdb" again.

    - xrdb will by default run your .Xresources file through cpp.  When
      your resources are split out into multiple resource files and
      then loaded by the individual client programs, they will not.
      WATCH OUT FOR THIS!!

      I had C style comments in my .Xresources file, which cpp stripped
      out.  When I switched to this method of distributed resource
      files I spent several frustrating days trying to figure out why
      my clients were not finding their resources.  Xt did *NOT*
      provide any error message when it encountered the C style
      comments in the resource files, it simply, silently, aborted
      processing the resource file.

      The loss of preprocessing (which can be very handy, e.g. ``#ifdef
      COLOR'' ...) is enough to cause some people to dismiss this
      method of resource management.

    - You may also run into some clients which break the rules.  For
      example, neither Emacs (18.58.3) nor Xvt (1.0) will find their
      resources if they are anywhere other than in .Xresources.

    - when starting up a client on a machine that does not share files
      with the machine where your resources are stored, your client
      will not find its resources.  Loading all your resources into the
      server will guarantee that all of your clients will always find
      their resources.            Casey Leedom ([e-mail])

  A possible compromise that I have tried, is to put resources for all
  my heavily used clients (eg: xterm) into my .Xresources file, and to
  use the "separate resources files" method for clients that I seldom
  use.

Define Your Display Properly
- - - - - - -

  Client programs are often executed on the same machine as the server.  In
  that situation, rather than setting your DISPLAY environment variable to
  "<hostname>:0.0", where <hostname> is the name of your workstation, you
  should set your DISPLAY variable to "unix:0.0" or ":0.0".  By doing this
  you access optimized routines that know that the server is on the same
  machine and use a shared memory method of transferring requests.
            [thanks to Patrick J Horgan ([e-mail])]

  See the _DISPLAY NAMES_ section of the X(1) man page for further
  explanation of how to properly set your display name.

  "I don't think it's stock MIT, but (at least) Data General and HP have
  libraries that are smart enough to use local communication even when
  the DISPLAY isn't set specially."
                  Rob Sartin (88opensi![e-mail])

  [Jody Goldberg ([e-mail]) sent me an Xlib patch to change
  stock R5 to use local communication even if DISPLAY is not properly set.
  I don't want to get in the business of distributing or trying to juggle
  non-MIT patches and so have elected not to include it here.  Hopefully MIT
  will apply this minor (~8 lines) patch themselves.  In the meantime, if
  you want to try it yourself, email Jody.  --ed.]

-------
Clients
-------

  If you only have a few megabytes of Ram then you should think
  carefully about the number of programs you are running.  Think also
  about the _kind_ of programs you are running.  For example:  Is there
  a smaller clock program than xclock?

  Unfortunately, I haven't really noticed that programs advertise how large
  they are, so the onus is on us to do the research and spread the word.

  [ Suggestions on better alternatives to the some of the standard clients
  (eg: Xclock, Xterm, Xbiff) are welcome.  --ed.]

  I've received some contradictory advice from people, on the subject
  of X client programs.  Some advocate the use of programs that are
  strictly Xlib based, since Xt, Xaw and other toolkits are rather
  large.  Others warn us that other applications which you are using
  may have already loaded up one or more of these shared libraries.  In
  this case, using a non-Xt (for example) client program may actually
  _increase_ the amount of RAM consumed.

  The upshot of all this seems to be: Don't mix toolkits.  That is, try
  and use just Athena clients, or just Xview clients (or just Motif
  clients, etc).  If you use more than one, then you're dragging in
  more than one toolkit library.

  Know your environment, and think carefully about which client
  programs would work best together in that environment.

          [Thanks to: Rob Sartin (88opensi![e-mail]),
      Duncan Sinclair ([e-mail] | [e-mail]) ]

A Better Clock for X
- - - - - - - - - - -

1) xcuckoo
   suggested by: Duncan Sinclair ([e-mail])
   available: on export.lcs.mit.edu

   Xcuckoo displays a clock in the title bar of *another* program.
   Saves screen real estate.

2) mclock
   suggested by: der Mouse ([e-mail])
   available: larry.mcrcim.mcgill.edu (132.206.1.1) in /X/mclock.shar

   Non Xt-based.  Extensively configurable.  it can be made to look
   very much like MIT oclock, or mostly like xclock purely by changing
   resources.

  Of course, the ultimate clock --- one that consumes no resources, and
  takes up no screen real estate --- is the one that hangs on your wall.
  :-)

A Better Terminal Emulator for X
- - - - - - - - - - - - - - - - -

  From the README file distributed with xterm:

  +-----
  |         Abandon All Hope, Ye Who Enter Here
  |
  | This is undoubtedly the most ugly program in the distribution.
  | ...
  +-----

  Ugly maybe, but at my site it's still the most used.  I suspect that
  xterm is one of the most used clients at many, if not most sites.
  Laziness?  Isn't there a better terminal emulator available?  See below.

  If you must use xterm, you can try reducing the number of saveLines
  to reduce memory usage.  [ Oliver Jones ([e-mail]),
           Jonny Farringdon ([e-mail]) ]

1) Xvt
   Suggested by: Richard Hesketh ([e-mail])
   Author: John D. Bovey ([e-mail])
   Available: export.lcs.mit.edu in /contrib/xvt-1.0.tar.Z

   [From the README file] "Xvt is an X terminal-emulator that is
   designed to be more or less compatible with xterm while using much
   less swap space.  It is mainly intended for use at sites which use
   large numbers of X terminals but may also be useful on single
   workstations that are short of memory.  On a [SunOS 4.1.* Sparc], an
   initially invoked xvt uses about 1/3 megabyte of swap while xterm
   uses about 1.3 megabytes (obtained by running pstat rather than ps
   which seems to give unreliable size figures on SPARCs).  The main
   way that xvt achieves its small size is by avoiding the use of the X
   toolkit."

   Since it is a partial 'clone' of xterm, you don't have to rename
   your resources, as xvt pretends to be "XTerm".  In it's current
   version, you cannot bind keys as you can in xterm.  I've heard that
   there are versions of xvt with this feature, but I've not found any
   yet.

   UPDATE (Oct 1993):  John Bovey tells me that a new version of xvt is
   in the works that should have some of the most frequently missed
   xterm features.

   There have been some conflicting opinions aired over xvt vs. xterm.
   Different sites with different needs will likely have to do
   their own evaluation.  Caveat Emptor, your mileage may vary.

   I have seen hard data from J.Bovey showing how xvt does in fact
   require less swap space than xterm.  However, both of us would still
   like to see any other benchmarks that people can provide comparing
   the two.  (eg: How much RAM each occupies, relative speed of each.)

2) rxvt
   Suggested by: Zack Evans ([e-mail])
   Author: Rob Nation ([e-mail])

   Apparently a stripped down Linux port of xvt, with some
   minor modifications.

3) mterm
   Suggested by/Author: der Mouse ([e-mail])
   Available: larry.mcrcim.mcgill.edu (132.206.1.1) in
     /X/mterm.src/mterm.ball-o-wax.

   "I also have my own terminal emulator.  Its major lack is
   scrollback, but some people like it anyway."

Other Client Comments
- - - - - - - - - - -
  When using the xlock screen locking client, the "qix" mode is
  much more lightweight than the default mode.
                 [Q. Alex Zhao ([e-mail])]

  I can confirm the previous report from personal experience  here.  In
  a lab full of ~20 sun 3/80's all running the Xkernel software, the
  subnet was getting regularly clobbered.  This was tracked down to
  students running xlock.  Since these machines are all xterminals, the
  actual xlock program runs remotely, and generates a scary amount of
  network traffic to draw the default 'swarm' pictures on the screen.
  We have removed this program and replaced it with a much simpler
  screen locking program which simply blanks the screen.        [ed.]

  An improved xbiff: Xbuffy.  It can watch multiple mailboxes and can
  do a pop up showing the From and Subject line of incoming mail.
  Xbiff doesn't eat much memory and Xbuffy tends to be about the same
  (on the RS/6000, xbuffy tends use just a little less memory).  It is
  in the contrib directory on ftp.x.org.
                               [ Bill Pemberton ([e-mail]) ]

Tuning your client
- - - - - - - - - -

  Suggestions on how you can tune your client programs to work faster.

  From Scott Barman ([e-mail]) comes a suggestion regarding Motif
  Text Field Widgets:

    I noticed that during data entry into Motif text field widgets, I
    was getting a slight lag in response to some keystrokes,
    particularly the initial one in the field.  Examining the what was
    going on with xscope I found it.  It seems that when the resource
    XmNblinkRate is non-zero and the focus is on a text field widget
    (or even just a text widget) the I-beam cursor will blink.
, the
    widget code is making a request to the server (CopyArea).  The user
    can stop this by setting the resource XmNblinkRate to 0.  It is not
    noticeable on a 40MHz SPARC, but it does make a little difference
    on a [slower system].

  This specific suggestion can probably be applied in general to lots
  of areas.  Consider your heavily used clients, are there any minor
  embellishments that can be turned off and thereby save on Server
  requests?

-------------------------
Miscellaneous Suggestions
-------------------------

Pretty Pictures
- - - - - - - -
  Don't use large bitmaps (GIF's, etc) as root window backgrounds.

  - The more complicated your root window bitmap, the slower the server
    is at redrawing your screen when you reposition windows (or redraw, etc)

  - These take up RAM, and CPU power.  I work on a Sun SPARC and I'm
    conscious of performance issues, I can't comprehend it when I see
    people with a 4mb Sun 3/60 running xphoon as their root window.

    I'll let someone else figure out how much RAM would be occupied by
    having a full screen root image on a colour workstation.

  - If you're anything like me, you need all the screen real estate
    that you can get for clients, and so rarely see the root window anyway.

              [ Thanks to Qiang Alex Zhao ([e-mail])
            for reminding me of this one. --ed.]

A Quicker Mouse
- - - - - - - -
  Using xset, you can adjust how fast your pointer moves on the screen
  when you move your mouse.  I use "xset m 3 10" in my .xinitrc file,
  which lets me send my pointer across the screen with just a flick of
  the wrist.  See the xset man page for further ideas and information.

  Hint: sometimes you may want to *slow down* your mouse tracking for
  fine work.  To cover my options, I have placed a number of different
  mouse setting commands into a menu in my window manager.

  e.g. (for twm) :
      menu "mouse settings" {
        "Mouse Settings:"            f.title
    "  Very Fast"                ! "xset m 7 10 &"
    "  Normal (Fast)"            ! "xset m 3 10 &"
    "  System Default (Un-Accelerated)"    ! "xset m default &"
    "  Glacial"                ! "xset m 0 10 &"
      }

Programming Thoughts
- - - - - - - - - - -
  Joe English ([e-mail]) :
    To speed up applications that you're developing, there are tons of
    things you can do.  Some that stick out:

    - For Motif programs, don't set XmFontList resources for individual
      buttons, labels, lists, et. al.; use the defaultFontList or
      labelFontList or whatever resource of the highest-level manager
      widget.  Again, stick to as few fonts as possible.

    - Better yet, don't use Motif at all.  It's an absolute pig.

    - Don't create and destroy widgets on the fly.  Try to reuse them.
      (This will avoid many problems with buggy toolkits, too.)

    - Use a line width of 0 in GCs.  On some servers this makes a HUGE
      difference.

    - Compress and collapse multiple Expose events.  This can make the
      difference between a fast application and a completely unusable
      one.

  Francois Staes ([e-mail]) :
    Just a small remark: I once heard that using a better malloc
    function would greatly increase performance of Xt based
    applications since they use malloc heavily. They suggested trying
    out the GNUY malloc, but I didn't find the time yet. I did some
    tests on small programs just doing malloc and free, and the
    differences were indeed very noticeable ( somewhat 5 times faster)

  [ Any confirmation on this from anyone?  --ed.]

  Andre' Beck ([e-mail]) :

  - Unnecessary NoExpose Events.

    Most people use XCopyArea/XCopyPlane as fastest blit routines, but
    they forget to reset graphics_exposures in the GC used for the
    blits. This will cause a NoExpose Event every blit, that, in most
    cases, only puts load onto the connection and forces the client to
    run through it's event-loop again and again.

  - Thousands of XChangeGC requests.

    This "Gfx Context Switching" is also seen in most handcoded X-Apps,
    where only one or few GCs are created and then heavily changed
    again and again.  Xt uses a definitely better mechanism, by caching
    and sharing a lot of GCs with all needed parameters. This will
    remove the load of subsequent XChangeGC requests from the
    connection (by moving it toward the client startup phase).

Say What!?
- - - - - -
  Some contributors proposed ideas that seem right off the wall at first:

  David B. Lewis (by day: [e-mail], by night: [e-mail]) :
    How about this: swap displays with someone else. Run all your programs
    on the other machine and display locally; the other user runs off your
    machine onto the other display. Goal: reduce context switches in the
    same operation between client and server.

  I'm not in a situation where I can easily try this, but I have received
  the following confirmation...

  Michael Salmon ([e-mail]):
    I regularly run programs on other machines and I notice a big
    difference. I try to run on a machine where I will reduce net usage
    and usually with nice to reduce the impact of my intrusion. This
    helps a lot on my poor little SS1+ with only 16 MB, it was
    essential when I only had 8 MB.

  Casey Leedom ([e-mail]) :
    [The X11 Server and the client are] competing for the same CPU as
    your server when you run it on the same machine.  Not really a
    major problem, except that the X11 client and the server are in
    absolute synchronicity and are context thrashing.

  Timothy H Panton ([e-mail]) :
    Firstly it relies on the fact that most CPU's are mostly idle, X's
    cpu usage is bursty.  so the chances of you and your teammate
    doing something cpu-intensive at the same time is small. If they
    are not then you get twice the cpu+memory available for your
    action.

    The second factor is that context switches are expensive, using 2
    cpu's halves them, you pay a price due to the overhead of going
    over the network, but this is offset in most cases by the improved
    buffering of a network (typically 20k vs 4k for a pipe), allowing
    even fewer context switches.

----------------------------
Other Sources of Information
----------------------------

The "Other X FAQ"
- - - - - - - - -

  David B. Lewis ([e-mail]) maintains the informative and
  well written "comp.windows.x Frequently Asked Questions" document.
  Its focus is on general X information, while this FAQ concentrates
  on performance.

  The comp.windows.x FAQ does address the issue of speed, but only with
  regards to the X server.  The gist of that topic seems to be:
    "Use X11R5, it is faster than R4".
  (Please see the X FAQ for complete details).

Books & etc.
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  Volume 8 in O'Reilly's X Window System Series; ``X Window System
  Administrator's Guide'' is a book that all X administrator's should
  read.

  Adrian Nye ([e-mail]):
    A lot more tips on performance are in the paper "Improving X
    Application Performance" by Chris D. Peterson and Sharon Chang, in
    Issue 3 of The X Resource.

    An earlier version of this paper appeared in the Xhibition 1992
    conference proceedings.

    This paper is absolutely essential reading for X programmers.

--------------
Author & Notes
--------------
  This list is currently maintained by Art Mulder ([e-mail])

  Suggestions, corrections, or submission for inclusion in this list
  are gladly accepted.  Layout suggestions and comments (spelling
  mistak's too! :-) are also welcome.

  Currently I have listed all contributors of the various comments and
  suggestions.  If you do not want to be credited, please tell me.

  speedup-x-faq is copyright (c) 1993 by Arthur E. Mulder

  You may copy this document in whole or in part as long as you don't
  try to make money off it, or pretend that you wrote it.

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--
 ...art mulder ( [e-mail] )    | "Do not be conformed to this world,
 http:   |  but be transformed by the renewal
 CS Dept, U of Alberta, Edmonton, Canada |  of your mind, ..."  Romans 12:2