1000 HZ kernel causes Doom3/Prey/Quake4 slowdown

[apeitheo]

I would like to set the timer frequency of my kernel to 1000 HZ (as id software suggests to run Enemy Territory: Quake Wars at its full potential), but doing so causes any of the games that use the Doom 3 engine to slow down with the FPS rapidly fluctuating. ETQW's performance is increased, however.

When the timer frequency is 250 HZ, I am able to get 63 FPS (seems to be where it's capped at) 99% of the time on Doom 3 even with 16AA & 16AF. Setting the timer frequency to anything higher than 250 HZ causes the slowdown (even setting it to 300 HZ causes the same problem). The FPS rapidly fluctuates around 20-50 FPS, even while standing still.

I've noticed that setting CONFIG_HIGH_RES_TIMERS=y in the kernel even with 250 HZ will cause this same problem as well, but I don't know what to make of it.

What's even stranger is that the windows Doom 3 client works fine under Wine even when 1000 HZ is set (60+ FPS).

Am I using the wrong timer or something? Any information at all to push me in the right direction would be highly appreciated.

Thank you

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AMD Athlon II X2 250
EVGA Nvidia 9800 GTX+
2X2GB DDR3 1066 RAM

[shazeal]

1000hz is for single CPU, you should use 250 for dual core. I have seen some patches in ZEN? that have a better timer for dual core.

The hz rating is per core, so if you set 1000hz you are actually running 2000hz, IIRC that is.

[darklegion]

Yeah, it's 432hz for a dual core in zen, 216hz for a quad core, and 864hz for a single core.

[Hyper_Eye]

I am very curious to find out if you have learned anything more about this. In particular... 1) what frequency ultimately worked better for you and 2) Did you find it better to enable or disable high res timers? Just to see if there is any discernible difference I am trying Zen sources right now and I am trying out the 216Hz frequency.
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[d2_racing]

Is there any doc about the right freq to use ?

[PaulBredbury]

Smoothness is achievable in single-player, with:

[PaulBredbury]

The 7.5.1 release notes for mesa have this line:

[apeitheo]

I found a solution..

I had to change my clocksource to "jiffies." I didn't find this fix anywhere online.. I was just playing around with everything I could find and then all of a sudden it worked when I changed this.

For those who are having the same problem:

[Hyper_Eye]

You should take the solved off so this thread doesn't get ignored. I would really love more information about your clocksource and why it solved your issue.
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[apeitheo]

[PaulBredbury]

apeitheo, it sounds like something wonky with your motherboard. Which particular motherboard model do you have?

[apeitheo]

[kernelOfTruth]

*subscribes*

interesting topic

I think I might need to experiment with my clocksource-setting too and see whether that fixes some jerkiness ...
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Hardcore Gentoo Linux user since 2004

[Aphax]

I'm very happy I ran into this thread, I've been having jerkiness in Doom3/Quake4/ETQW for such a long time and tried so many things to solve it I had mostly given up. Long ago Doom3 ran really well on my PC, but somewhere along the way I got the same jerkiness issue. Interestingly I got this on at least 2 mostly different PCs I tried (one amd, one intel CPU, one with ATI graphics, the other Nvidia...), what made it worse was that I couldn't find much through google about this specific issue (or rather, tons of 'noise' from of people with seemingly unrelated FPS problems).

I spent considerable time trying to figure out what causes it, trying dozens of different timer-related kernel options, different kernel versions and so on, and I only got Doom3 running smoothly again using either <2.6.24 for 64bit, or <2.6.20 for 32bit, interestingly these were also the versions in which they introduced the tickless kernel thing (I may have incorrectly remembered the exact kernel versions mentioned here). Simply disabling dynamic ticks didn't help though, but still it seemed something related to the timing code changed that must somehow subtly break Doom3's timing code for me.

Anyway, this thread has given me a few more things to try (since I don't really want to run an ancient kernel version), so thanks :p

PS. I just tried changing clocksource to jiffies, but that seems to just make my machine to freeze after a few seconds (I guess this is because I actually have dynamic ticks enabled at the moment). I'll try a few things and let you know if I manage to fix it


EDIT: Well that's just damn typical.. tried various combinations of the things mentioned in this thread (250 and 300Hz kernels, different clock sources) and none seemed to help. I could not however try 'jiffies' as clocksource because the second I set it to that, my machine locks up again, even though I have dynamic ticks turned off (I double checked /proc/config.gz just in case I forgot to actually boot the new kernel, which happens sometimes).
Meh

[PaulBredbury]

Sounds like Con's new scheduler helps too:

[apeitheo]

[kernelOfTruth]

[Aphax]

Success! I was indeed setting it through /sys, so as you suggested I tried setting it as a boot parameter which worked, and now together with a tickrate of 250HZ (didn't try jiffies with 100/300/1000HZ yet) Doom3 runs smoothly at last

EDIT: Just for the record, even with 1000HZ Doom 3 is smooth now, simply passing clocksource=jiffies in my bootparams is all it really takes for me

[saint_abroad]

BTW, are you using CPUFREQ? What about dynamic ticks?
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[Aphax]

[Aphax]

Small update, 'jiffies' as clocksource causes timer problems on my new pc (Core i7 870, Gigabyte GA-P55-USB3 mobo), as time now seems to 'pass' too slowly (affecting everything including things like keyrepeat rate). So I'm back to square one :/ Not that I really run any D3 based games anymore, but it still kind of bugs me

[PaulBredbury]

I suggest you use pf-sources then. It's what I use.

[Ivan The Viking]

I am using pf-sources with the BF scheduler, no issues as mentioned here with 1000hz ticks.
When I try gentoo-sources I get the 'stuttering' in doom3 and quake 4.
I recommend trying pf-sources out, or to patch in that scheduler.

[whig]

I solved etqw jerkiness and crashes, progressively getting worse, by deleting ~/.etqwcl.

[PaulBredbury]