Messages in this thread | | | Subject | Re: [REPORT] cfs-v4 vs sd-0.44 | From | Arjan van de Ven <> | Date | Mon, 23 Apr 2007 21:52:03 -0700 |
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> 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.
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.
-- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
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