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A Low-Latency Kernel For Linux Gaming

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  • #41
    Originally posted by Paradox Uncreated View Post
    Latency

    And frames above 73hz really isn`t useful anyway.
    .
    Just FTR that statement may only have meat on the bones if your refresh rate is at or under 73Hz. Back when games allowed extreme user control but still in effect today, setting FPS to match Refresh made for extreme smoothness. For example capping Quake 3 Arena at 120FPS and setting Refresh to 120 Hz makes tricks possible that are extremely fifficult or even impossible at different settings. It is my understanding that this creates a hard sync in timing and i can assure you, whatever the cause, you can feel it. This of course assumes your monitor is capable of 120Hz.

    Note - Yeah I know Q3 is a 20+ year old game and even those that still play it are mostly on Quake Live, but the effect is the same and afaik independent of the game being a natural timing issue.

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    • #42
      And update on what I said on 72/73 hz refresh/FPS, I think 30 fps is quite sufficient on 4K, so the resolution and detaillevel you run definately has something to say on that.

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      • #43
        Talking of resolution I later found an undocumented maximal antialiasing mode I used on 4K, and ran the old game Unreal at 30 fps, and it looked and played great. This on windows though, but it probably is possible somehow to do this on linux aswell(?)



        One frame = 25 MB Lol..

        As I wrote on this: The new mode is demonstrated here on Unreal "Skaarj Generator" in 4k + the undocumented 3x3 Supersampling + 4x SGSS -no MSAA- Nvidia mode. They complement eachother, aligning to the highest possible antialiasing. Furthermore anisotropic optimizations must be off, and filtering set to 2x, and LOD Bias -0.5. This is near the very optimal of psychovisual "high resolution", so an ultimate setting! Not documented, but possible.

        You may need a compatibility bit if you are going to try it on windows, I found it on a german site, also.






        Last edited by Paradox Ethereal; 06-23-2017, 10:04 AM.

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        • #44
          As for benchmarking jitter/latency, more tools exist for this now it seems:

          https://lwn.net/Articles/725238/

          So the linux kernel might be getting better at this all the time! And my impression is that many linux engineers care more about this, than windows, so.. However if windows fixed their jitter aswell, it would indeed be a good OS, and with its software support, be a winner. People still complain about lost frames and untight timing etc, on windows tough. And I have never heard of anyone doing close 0.33ms audio on it. Some technical papers on windows still talk about 10ms as a good latency target, indeed (LOL).

          Best Regards.

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          • #45
            Originally posted by RCL_ View Post
            Modern games stabilized around two numbers: 30 FPS (mostly console games) and 60 FPS (PC games). 30 FPS is the lowest acceptable FPS, and it's chosen out of necessity, because it turns out that some people prefer (with their dollars) richer graphics (possible with 33 ms per frame) over smoother experience.

            As for network games, network latency (ping to server) is rather orthogonal aspect to visual latency because of two factors:

            1) ALL network games [try hard to] predict server response in advance (by essentially running the same code - on possibly stale/incomplete data - on clients) and then correct/compensate/lerp after getting authoritative server data. Games would be unplayable if you there was a delay of 20-50 ms between you pressing forward and you actually moving forward.

            2) Game tick (i.e. when game entities are updated, when they "think" - which in network client-server based games only happens on servers) already happens at different (often lower) rate than drawing. For user experience, it's much more important to update animations (which often are local to clients), non-game-affecting physics (particles, smoke, etc), and other "visual" things in a network game, which happens client-side.


            P.S. When talking about games, it's misleading to use FPS. It's better to compare frame time in milliseconds, and for latency tests, it's better to compare standard deviation of this value instead of an "average FPS".
            Used to be 60 for PC. It's tilting towards 120Hz and 144Hz more and more. Bunch of such specialized monitors on gaming peripherals market.

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            • #46
              When jitter is getting low, hardware latencies matter aswell ofcourse. http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Latency-Test

              I think in the end, low jitter is what everybody wants from large many cpu machines, to multicpu home computers. It really makes an OS feel high-end, good and responsive, with very low latencies possible, and smooth graphics. So in that, the standard linux config really should be low-jitter

              Best Regards.
              Last edited by Paradox Ethereal; 06-23-2017, 02:51 PM.

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              • #47
                ping Paradox Uncreated - I don't understand why windows users who already have over 90% of the Desktop market need to delude themselves that Windows does everything best. Maybe it does Desktops best for Average Joe non-technical user but it should be obvious it doesn't do everything best or Linux wouldn't have more support for more platforms and be used on everything from embeddeds, thru smartphones, to Supercomputers. I am so sick of hearing Windows users buy into the MS Spin that Windows, especially Win 10, revamped the whole latency issue and can now achieve down to 1 msec latency. Baloney! That is a damned lie when one considers the system as a whole because there is no way MS is going to make a kernel that so many of it's clients can't run because their hardware is run-of-the-mill crap.

                BOTTOM LINE - Windows' kernel has not changed and won't change in this area.. All that has changed is priority scheduling and a suggestion to turn off services....period! The prime obstacle through which all software must operate to reach hardware is the kernel and MS doesn't even offer an optional low-latency kernel. BSODs caused by allowing software direct access to hardware is a thing of the past ONLY because that mistake was rectified after a scanner crashed Win 98 SE when it was plugged in on Live TV. It took a few years but direct access was discontinued and the embarrassment still haunts them. Everything goes through the kernel now and since Win 2K and that kernel is conservatively designed for 16-20 msec.

                Specific to gaming, Windows still has some advantages but latency isn't one of them.

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                • #48
                  Windows does not do everything best, but it does enough things simply better or does offer more options. More enough so that majority of users are not willing to put up with design and functionality issues inherent to "free Linux software". Open software tends to be pile of individual small or bigger programs. Some work reasonably well, some should have devs shot because of UI/functionality design. MS software tends to be far more deeply integrated to work with each other to the degree that there is often enough no real alternatives to using it. And windows software in general often has no analogues among "Linux software"

                  Be it office, gaming or daily use.

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                  • #49
                    Yes, windows 10 seems to have technical papers stating, "before we had 10ms latency, now we have 1.3ms". I havenĀ“t tried it, since the online world seems to be complaining about the same still. And also having used 0.33ms latency on linux, which is a strongpoint of it, I have already tried lower latencies. And it really is where things start to get interesting for me. It seems when average and peak jitter is below 0.2ms, that ultrasmooth graphics and responsive desktop happens aswell. Getting latency even lower, and it is like playing hardware.

                    Bela talks about ultra low latency operation for audio aswell. However, as is with many of these things, do you bother to deal with the obsurity or just use some well supported platform, and deal with the kinda-boring OS-gets-in-the-way-due-to-boring-buffers-and-jittery-design-decisions?

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                    • #50
                      Originally posted by aht0 View Post
                      Windows does not do everything best, but it does enough things simply better or does offer more options. More enough so that majority of users are not willing to put up with design and functionality issues inherent to "free Linux software". Open software tends to be pile of individual small or bigger programs. Some work reasonably well, some should have devs shot because of UI/functionality design. MS software tends to be far more deeply integrated to work with each other to the degree that there is often enough no real alternatives to using it. And windows software in general often has no analogues among "Linux software"

                      Be it office, gaming or daily use.
                      Since this thread is titled specifically "Linux kernel" I have to wonder what even brought you here but that's OK assuming you came to enhance your knowledge. However if you came just to defend "ur fave" kindly refrain from talking smack about things of which you know little or nothing.

                      There is a reason each OpSys has the share they do. Windows rules on the Desktop niche because the average user cares not to know about "nuts and bolts" just like many drivers can't even change a tire, let alone rebuild an engine. Linux is on everything from embeddeds to SuperComputers not because it is free as in no cost but because it is Free as in having the freedom to customize for specific usage. I've been using Linux since 2001 and there was a time I did a lot of dualbooting....about 1 year. By 2002 Linux became my main and I have uptimes in excess of 14 months and I'm not one who uses a PC for just email and facebook.

                      FWIW even though I happily spent over $1200 USD for my DAW which for years only ran in Windows, not only did it slowly get eclipsed by Ardour but for the past 2 years the "windows-only" DAW runs happily in Wine. There is absolutely nothing I want nor need to do that Linux won't do and a whole lot that Windows does that I don't want and certainly don't need.

                      The "deep integration" you speak of is a flaw as in "all eggs in one basket". It requires devs provide DLLs since they have no idea what version each client will be using. This increases bloat which in Windows' case is often actually using resources for "readiness". Additionally since any installed application must make a Registry entry (as well as prefers to be in "C:\Program Files") in any version it is far more hacker friendly, easy to navigate. With Win 10 EULA in which you sign away your right to any privacy and everything including your emails even if your entire disc is encrypted, can be read by Microsoft and "phoned home", your ownership is a farce and your security compromised. Then of course we have Latency, completely out of your control.

                      I'm sorry Bro, as of this date, you simply don't know what your talking about when you characterize Linux. You're free to learn, but you haven't yet. Simple fact. Windows is not better. It's just a wee bit easier and that gap is closing ever since Ubuntu was born even though I personally wish Linux would not try to become "free windows". Everything is a tradeoff and I prefer the knowledge, control and Freedom.to mere convenience.

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