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A comment on Measuring Input Latency on Linux: X11 vs. Wayland, VRR, and DXVK. Parent comment

Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by hackernudes on Tuesday July 14, 2026 @02:04PM (#48910779)
I don't think there was ever a design to be one frame behind.

Compositing requires the GPU to do some extra work to draw the frame to be presented. This typically takes very little time (much less than a full frame period). Additionally, most wayland compositors will bypass that extra step if an application is full screen (wlroots calls it "direct scanout").

Also some wayland compositors keep track of timing and delay the final composition until right before it is time to present the frame in order to reduce latency.

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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by gf000 on Tuesday July 14, 2026 @03:32PM (#48911902)
And for the complete picture, X is predominantly used with a compositor, so that same extra latency exists there as well.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by cwillu on Tuesday July 14, 2026 @04:50PM (#48912775)
It's generally a single checkbox to turn off compositing in X11, for precisely this reason.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by FeepingCreature on Tuesday July 14, 2026 @04:55PM (#48912829)
You can also disable compositing conditionally in KDE, such as when a game window is opened.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by Chu4eeno on Tuesday July 14, 2026 @06:03PM (#48913475)
Not in Wayland, the whole point of Wayland is to make stuff the X server + compositor + various other bits into the window manager.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by gf000 on Wednesday July 15, 2026 @09:03AM (#48920232)
For full-screen applications, Wayland has a protocol to let it display frames at its own pace - meant mostly for games for this very reason.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by FeepingCreature on Wednesday July 15, 2026 @10:19AM (#48921241)
With X11, you can disable composition for windowed apps as well.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by preg_match on Wednesday July 15, 2026 @01:58PM (#48924706)
Yes, but the same is true in Wayland and it's automatic as well. Full screen applications don't require compositing so they typically don't, and this was the case in MOST X11 compositors as well.

Turning off compositing before launching a game is maybe a bit misguided, sort of like turning on the "classic theme" in Windows 7 before launching a game. It might save some memory, sure, but latency should be identical.

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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by cwillu on Wednesday July 15, 2026 @05:50PM (#48927524)
> latency should be identical

Should be, but very clearly isn't.

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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by preg_match on Wednesday July 15, 2026 @11:45PM (#48930111)
The results show it's identical. Only XWayland suffered any significant degradation, and even then we're talking <5ms which is imperceptible.
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Re:Measuring Input Latency on Linux: X11 vs. Wayland, VRR, a... by cwillu on Thursday July 16, 2026 @01:56AM (#48930823)
Those results depend on having a 500hz monitor. There's a world of difference between a mildly-buggy rendering loop's 1-frame delay or missing a vsync deadline causing a 2ms delay vs a 16ms delay.
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