Messages in this thread | | | Date | Tue, 24 Apr 2007 16:21:28 +1000 | From | Peter Williams <> | Subject | Re: [REPORT] cfs-v4 vs sd-0.44 |
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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 pwil3058@bigpond.net.au
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