Benchmarking The Ubuntu "Low-Jitter" Linux Kernel

[Paradox Ethereal]

PS: Currently tring 3.6.2-rt4 (realtime patch) which will probably be used in next version.

Peace Be With You.

[gamerk2]

gamer2k completely misses both the point and the benchmark again, and states an old argument not relevant to this about "latency vs throughput". So if you increase latency on a c64, does it get more throughout? (*laugh here*)

Considering the C64 didn't have a pre-empting kernel, no. But in a pre-empting kernel, every time you switch from task "x", "x" is not getting work done. So you decrease system latency, but you increase the time it takes "x" to finish.

Hell, I could switch tasks with every tick of the CPU clock if I wanted to. Every system related task would be uber-snappy as a result. Any actual usespace program would run like crap though.

Obviously some people think jitter is "disk-io". If you have reduced "disk-io" with there being the same disk i/o, you know jitter is lower. (lol)

Do you have any idea how a modern pre-emptive scheduler works? If some thread needs to access the disk, it should be preempted (can not run). No matter how fast you make the rest of the system, you have a bottleneck that exists for that given thread, that you can NOT solve in S/W.

You are the worst type of developer: One who makes changes, convinced he is right, without testing every possible outcome. Then when people tells him the downsides to his approach, he ignores them. And when people start to tell him he outright breaks stuff, he laughs at them. Then people like me get paid to clean up the mess you leave behind.

[Paradox Ethereal]

I don`t know how gamer2k can even reply with this garbage.

Anyway, it seems that jitter is known on windows as "microstutter". And Battlefield 3 measures it as "frametime". So, having set some attention on it, hopefully there will come attention and benchmarks on it, for linux aswell.

Peace Be With You.

[liam]

PS: http://en.wikipedia.org/wiki/TRON_Project

Tron OS did realtime in 1984. Was forced off the market by MS.
MS sees cp/m, copies it, although it is shit. Sells it to you.
MS sees unix windowmanager, copies it, sells it to you as windows, now with extreme latency. The very other end of realtime you might say. (nontime? sleepingbag-time?)
MS sees windowsblinds, copies it, another service on top of a poor scheduler and sells it to you.
200 things in modern windows OS, can be turned off, leaving a BETTER computer. What are they doing being developed, and included in the price of the product sold to you?
MS teaches obscure non-streamlined windows menus, and encourages people to not turn off these things, buying their whole corporate propaganda, and certifies people for this? What do you call that?

Linux is open-source, and can be modified by anyone, patches are often made in days, and emails to developers read in minutes.
By the time a fix may already be suggested on LKML, you have reached "I need to establish identiy please, I cannot hear you please" on MS support, phone to another country.

And that is ofcourse just some of it.

And then MS lanches it`s own OS, as a cure for headaches in their current (they did this with 98)

It`s mad, and serves no human.

Peace Be With You.

Any particular reason you aren't using the preempt_rt rather than just the preempt?
For what it's worth I think an RTOS is the obvious choice for gaming but you simply can't expect throughput to go up as a result (which you seem to think can happen). Rather, throughput is almost certainly going to go down, but I personally don't think that loss is of great significence for the Desktop market. The potential for increased interactivity and reliable responses is, as you've said, so nice.

[Paradox Ethereal]

How many times do I have to say this. Framejitter, reduces performance. A high end machine with jitter, acts similarly to a low-end machine.

If jitter reduces ACTUAL frames outputted to screen to 30fps, what are you talking about throughput for?
Don`t confuse SERVER throughput, that needs no graphical environment, to GRAPHICS throughput.

And because of performance, I have said I only look to 0.2ms max latency/jitter. Currently I use the "low latency" desktop, in the rt-patch still, but I may increase the preemption level. Not without reasons, not "loosing performance". Only if it becomes better. No senselessness, only optimality. Don`t worry, and stop the silly "throughput" arguments.

Peace Be With You.

[Sidicas]

Oh God, another thoughput guy. How many times do I have to say this. Framejitter, reduces performance. A high end machine with jitter, acts similarly to a low-end machine.

I think "responsiveness" is the better word to use there rather than performance.

"Performance" as most kernel devs call it is just the measure of how much work can be done in any given time. Improving responsiveness will almost always decrease "performance". Kernel devs focus a lot on performance and very little on responsiveness.. For gaming specifically, performance without responsiveness is a whole truck load of worthless.

Micro-stutter situations in Crossfire / SLI setups is another example of the focus on performance without responsiveness, although not all Crossfire / SLI setups have Micro-stutter, in fact I'd say, most don't.

[Paradox Ethereal]

How hard can this be to understand. What is completely obvious to me, is obviously very hard to understand for many.

I just had a whole thread, where people didn`t understand over at anandtech and eariler arsetechnica forum people, showed complete lack of understanding aswell.

I mean that is why I mention Einstein. He is doing math on infinity. And he is seen as a genious by most of the world. But it is no other than giving power to objects, like simpler people of uncivilized places do.

However if you excel, and have a mind, and make yourself known, you can do much more good for the mindless than themselves.

Mitt Romney “Even if we believed in ourselves, nobody else did”.

That is so true, if you excel, no-one is going to understand you or why.

John McCain, who has made some very clear observation on the Islam debate “Quran is good, sects are bad”.

II also wrote LKML on this:

As those who have seen my posts on LKML, I am all about jitter.
10 years ago I said why not do an OpenGL desktop, and now we have wayland.
10 years ago, I said, don`t do excessive buffering, and now we have "fighting bufferbloat".
10 years ago, I talked about how responsive vintage computers was, without "OS".

And I have taken that further, and now work with low-jitter for the desktop. Low latency all the way, or atleast down to 0.2ms max latency and jitter.

In the mean time, the masses are unaware of jitter, unless it is very noticable such as recent discussions on "microstutter".
Most still advise to "not turn off services" in windows, yet show me benchmarks of "motherboards" with DPC latency of 50-300uS. I am already running at 5uS in windows here. And it is not "the motherboard". This is about OS-jitter.

And in linux, I am running with even less jitter, now trying rt-patch only at "low latency" preemption yet, but still. And even in the linuxcommunity many seem not to understand. Those who do are much higher then on windows though. And while many also make completely absurd statements and attack what I am doing, I am very happily running what feels like a high performance computer. With a lot of activity being there on the next frame, and ultrasmooth framerates in OpenGL. Indeed optimizing and removing jitter, seeing improvements on what goes on, on the highest performing bus in the computer, seems to improve general desktop computing.

I think I have tried most things now, and unless you want to wait 10 years for people to catch on, you should consider low-jitter aswell.

And I am also interested in any patches that currently are not mainline. - Please repost in this thread if you have any. Or any other information, or ongoing development. If it is not all in the RT patch, that is.

Peace Be With You.


So then it is up to those who have a mind, or simply think this is a good thing to follow. Ultimately it trickles down to the masses aswell I guess. But now you have a chance to trim 10 years on that

Peace Be With You.

[Paradox Ethereal]

In The RME forum, I did a post on 5uS DPC latency in windows, that makes their hardware perform at 1ms latency in windows (stable), aswell.

[Paradox Ethereal]

On KVR some people prefer the audio from 1950 before the hifi-era. Elsewhere analog and vinyl are recommended.
I mean I could be jazzing on the utmost of excellent audio and video, and people would still be nonunderstanding.

[Paradox Ethereal]

Edit: outdated.