The Completely Fair Scheduler's Impact On Games

eldavojohn writes "We've heard a bit about the completely fair scheduler previously, but now Kernel Trap looks at the implications this new scheduler has for 3D games in Linux. Linus Torvalds noted, 'I don't think any scheduler is perfect, and almost all of the time, the RightAnswer(tm) ends up being not one or the other, but somewhere in between. But at the same time, no technical decision is ever written in stone. It's all a balancing act. I've replaced the scheduler before, I'm 100% sure we'll replace it again. Schedulers are actually not at all that important in the end: they are a very very small detail in the kernel.' The posts that follow the brief article, reveal that Linus seems quite confident that he made the right choice in his decision to merge CFS with the Linux kernel. One thing's for certain, gaming on Linux can't suffer any more setbacks or it may be many years before we see FOSS games rival the commercial world."

Comments

Article is misleading

[RailGunner]

Funny, in the article those framerates for Quake III show CFS beating the pants off of SD.

Besides, the biggest barrier to 3d games in Linux is video card drivers (ATI, I'm looking at you!) as 3D drivers in Linux, even the proprietary ones, have tended to be unstable.

Linus is right one this one, the scheduler is a small part.

Re:Article is misleading

[Omnifarious]

FPS is a poor measure of the feel of a game. I know it's what all the graphics card benchmarks use, and it does do a good job of measuring the total processor and video card throughput, but that's not the most important thing.

The most important thing is the time between you pressing a key and the changed game state being reflected on your screen and how consistent that delay is.

One of the arguments that CK has made about kernel development is that kernel developers have become obsessed with throughput to the exclusion of all else and that this leads to very poor desktop performance because throughput is a poor measure of 'interactivity'. Someone posting 3D game framerates as evidence of one scheduler being better than another is exhibiting exactly this bias.

IMHO latency is a better measure, but still not perfect and it can be hard to measure in some cases.

I don't know enough about the scheduler to know which one is better or which one exhibits particular properties. But I can see that the throughput bias is evidenced in force in the thread the article points to.

And CK is also right that big iron shops care more about overall throughput than any measure of 'interactivity'. IMHO there ought to be some kind of pluggable scheduler system that allows you to completely change the algorithm to reflect the preferred behavior of the computer you're using.

You won't get good games until you get marketshare

[nweaver]

This is irrelevant to the gaming front.

The limit to games on Linux is market share. Its not (much) easier to develop a good 3D game for linux as it is Windows, so why code for 2% of the market when you can code for 92% of the market?

Thus you will only get games where the developer has gone out of their way to ensure complete portibility and provides a port mostly out of courtousy.

The scheduler details are irrelevant for this: what Linux Games need is 10%+ marketshare on the desktop.