Re: Responsiveness of 2.6.0-Test9

From: Nick Piggin
Date: Mon Nov 03 2003 - 21:37:20 EST

Erwin Telser wrote:

Erwin Telser wrote:

Are there things to observe when switching from 2.4 to 2.6, if I want the
same responsiveness? I'm asking because I' ve made the following
observation. (I always had the feeling, 2.4 seems to faster, but this is
the first time it' s very obvious)

I' ve connected two monitors on a Matrox G550. One runs with DRI the other
one doesn't (not possible with the current driver). The Monitor with DRI
I'm using as a TV Set, watching movies with xawtv. (With a bttv 878 tuner

Now with the 2.4.22 kernel (preemptible patch aplied) I can play the
little game kbounce on the other monitor, without to notice any slowdown,
no matter, whether xawtv is running or not.

But with the 2.6 Kernel (compiled with preemptible option) the bouncing
balls slow down considerably, as soon as I move the mouse.

I know the whole thing is a little foolish. But anyway, are there some
tricks to get the same responsiveness?

Your report is not foolish at all ;)
Please make sure your X process is at default static priority, 0.
Report back if you are still having problems. What sort of processor
do you have? Is your 2.6 video driver running with the same sort of
acceleration as your 2.4 one (do you get the same frame rate in glxgears)?

I installed X from scratch and didn't edit any start script. so I assume, that it runs with priority 0. The processor is an Intel P4 2000MHz in an ASUS P4B266 Board. If I compare the frames per second with glxgears there is a slight advantage for 2.4

renice 0 `pidof X`

2.4: with DRI 358 - 364
without DRI 181 - 198

with DRI 350 - 362
without DRI 180 - 187

An even better way to show the differenze between 2.4 and 2.6 is to change the size of the xawtv window. If I do that, the slowdown is quite significant. But it happens only with xawtv. If I do the same with konqueror or MPlayer, nothing happens. A very strange thing are the values I get from ksysguard

Kernel 2.4, glxgears
user load: 3% - 4%
system load: 95%
IRQ per second: ~100

Kernel 2.6, glxgears
user load: 15%
system load: 85%
IRQ per second: ~1100

Kernel 2.4, xawtv
user load: 2%
system load: 0%
IRQ per second: ~100

Kernel 2.6, xawtv
user load: 9%
system load: 0%
IRQ per second: ~1060

Kernel 2.4, MPlayer
user load: 35%
system load: 2%
IRQ per second: ~1170

Kernel 2.6, MPlayer
user load: 42%
system load: 2%
IRQ per second: ~2130

Something is causing a high IRQ load with kernel 2.6. Probably an APIC problem?

It is the timer interrupt. Now happens 1000 per second instead of 100.
This might just be the reason why you are seeing a different balance, the
collection of cpu statistics is more precise.

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