Preemption: no go for gamers

T2 · n00b Joined: 01 Jun 2002 Posts: 67 Location: Slovenia

Hi!

First I'd like to say I like gentoo more and more. Yesterday I installed first three stages while playing wolfenstein using chroot magic (No, I don't like official install guide and I don't have PS to play with

One word to gamers: keep away from preemtion and low-latency kernel patches it will ruin your game performance. So go with vanilla (2.4.19pre9 currently); if you disable preemption patch in gentoo kernel sources there are chances build will fail like in my case.

Why am I saying that? With vanilla kernel I can process seti@home data and play wolfenstein over net smoothly (each take 50% on my TB900@980) but with any kernel that has preemption or low latency patch applied, I can hardly move the mouse, game behaves very very choppy and all is stuttering.
While I don't say that system with preemptible kernel isn't more responsive in some cases, however it offers worse real-time performance in hardcore gaming.

I don't have any deep knowledge on kernel schedualing so please correct me if I'm wrong.

regards

Malakin · Posted: Sat Jun 01, 2002 9:04 pm Post subject:

You had problems with the gentoo sources but you couldn't disable preempt since it caused problems. Vanilla worked fine for you. Did you actually add preempt to vanilla and have it cause the same problems you were having with the gentoo sources?

I'm using a 2.4.19-pre7 with preempt and it's been running great, gaming or otherwise. Preempt has been extremely tested so I'd be surprised to hear about any problems with it.

sibn · n00b Joined: 15 May 2002 Posts: 36

The last time I ever used preempt, it worked bad, bad magic with a lot of different things (for example, railroad tycoon 2).

It would cause hard system lockups (no ssh to reboot it, even) not five minutes into the game. Although it is entirely possible that this was an issue specific to the kernel version (and preempt version) that I was using at the time.

gentoo-sources-2.4.19* are not compatible with several things I require, so I'm currently using the vanilla 2.4.18 tree. When 2.4.19 is officially available, though, i'll check it out again and see what happens.[/b]
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radfaraf · n00b Joined: 25 May 2002 Posts: 55 Location: NJ

I use gentoo with preempt and it runs just fine, I run Wolfenstein too and its pretty much windows speed if not faster.

T2 · n00b Joined: 01 Jun 2002 Posts: 67 Location: Slovenia

Oh I forgot to say that I really want seti@home client to run in background. So gentoo-kernel (and all preemptible kernels I've tried like AC, MJ) work fine if I run only one main process (game

but when I add seti@home client in background wolfenstein gets "attention" from cpu every half second aprox. I haven't tweaked any process priority, maybe I should. Well with preemptible kernels I get feeling that background processes are stealing more cpu cycles from "focused" application than in vanilla-kernel case.

AutoBot · l33t Joined: 22 Apr 2002 Posts: 968 Location: Usually Out

I run both low latency and preempt all the while playing RTCW, and running a RTCW server, among other running task without any problems. Sorry I would have tried to word that better but one is too tired, oh and I have all that running on a 533mhz box so it must be some strange happening or I'm just lucky.
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felysium · n00b Joined: 27 May 2002 Posts: 43 Location: Netherlands

seti-home is a very very memory intensive program.
for example: when I ran seti@home on a BP6 (2xCeleron 550) there was a huge difference in completion time between 1 process and 2 processes.
With 1 process and only 1 processor being used the completion time was 8 hours. When I ran two processes the completion time was 12 hours. The 2 processes had to deal with the same mem.

BTW why do you want to run seti while playing w3d?

T2 · n00b Joined: 01 Jun 2002 Posts: 67 Location: Slovenia

T2 · n00b Joined: 01 Jun 2002 Posts: 67 Location: Slovenia

FINITE · Guru Joined: 10 May 2002 Posts: 449

Gentoo source works fine for me. My games all run quite fast.

pavera · Tux's lil' helper Joined: 27 May 2002 Posts: 84

I run Seti@home all the time in the background, I have the nice on it turned down to 19 though, so if I'm not running anything else it gets most of the CPU but as soon as I turn on anything else, it drops way off (depending on how much the other process is using), I have low latency and preempt, and everything runs fine.
nice --adjustment=19 ./setiathome -verbose
is the command I use to start setiathome...