Arjan van de Ven wrote:
Within reason, it's not the number of clients that X has that causes its
CPU bandwidth use to sky rocket and cause problems. It's more to to
with what type of clients they are. Most GUIs (even ones that are
constantly updating visual data (e.g. gkrellm -- I can open quite a
large number of these without increasing X's CPU usage very much)) cause
very little load on the X server. The exceptions to this are the
there is actually 2 and not just 1 "X server", and they are VERY VERY
different in behavior.
Case 1: Accelerated driver
If X talks to a decent enough card it supports will with acceleration,
it will be very rare for X itself to spend any kind of significant
amount of CPU time, all the really heavy stuff is done in hardware, and
asynchronously at that. A bit of batching will greatly improve system
performance in this case.
Case 2: Unaccelerated VESA
Some drivers in X, especially the VESA and NV drivers (which are quite
common, vesa is used on all hardware without a special driver nowadays),
have no or not enough acceleration to matter for modern desktops. This
means the CPU is doing all the heavy lifting, in the X program. In this
case even a simple "move the window a bit" becomes quite a bit of a CPU
hog already.
Mine's a:
SiS 661/741/760 PCI/AGP or 662/761Gx PCIE VGA Display adapter according
to X's display settings tool. Which category does that fall into?
It's not a special adapter and is just the one that came with the
motherboard. It doesn't use much CPU unless I grab a window and wiggle
it all over the screen or do something like "ls -lR /" in an xterm.
The cases are fundamentally different in behavior, because in the first
case, X hardly consumes the time it would get in any scheme, while in
the second case X really is CPU bound and will happily consume any CPU
time it can get.
Which still doesn't justify an elaborate "points" sharing scheme.
Whichever way you look at that that's just another way of giving X more
CPU bandwidth and there are simpler ways to give X more CPU if it needs
it. However, I think there's something seriously wrong if it needs the
-19 nice that I've heard mentioned. You might as well just run it as a
real time process.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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