Naturally these kinds of having a language island create some attrition regarding build tooling, integration with existing ecosystem and who is able to contribute to what.
So lets see how it evolves, even with my C bashing, I was a much happier XFCE user than with GNOME and GJS all over the place.
It is not the performance bottleneck people seem to believe.
Implementation matters, including proper use of JIT/AOT toolchains.
That's the easiest way you can win any argument on gnome. You're going straight for the nuclear option.
https://gitlab.xfce.org/xfce/xfwm4/-/blob/master/settings-di...
I think I know what "frame perfect" means, and I'm pretty sure that you've been able to get that for ages on X11... at least with AMD/ATi hardware. Enable (or have your distro enable) the TearFree option, and there you go.
I read somewhere that TearFree is triple buffering, so -if true- it's my (perhaps mistaken) understanding that this adds a frame of latency.
True triple buffering doesn't add one frame of latency, but since it enforces only whole frames be sent to the display instead of tearing, it can cause partial frames of latency. (It's hard to come up with a well-defined measure of frame latency when tearing is allowed.)
But there have been many systems that abused the term "triple buffering" to refer to a three-frame queue, which always does add unnecessary latency, making it almost always the wrong choice for interactive systems.
I ask because just a few minutes ago, I ran VRRTest [0] on my dual-monitor machine and saw no screen tearing on either monitor. Because VRR is disabled in multi-monitor setups, I saw juddering on both monitors when I commanded VRRTest render rates that weren't a multiple of the monitor's refresh rate, but no tearing at all.
My setup:
* Both monitors hooked up via DisplayPort
* Radeon 9070 (non-XT)
* Gentoo Linux, running almost all ~amd64 packages.
* x11-base/xorg-server-21.1.20
* x11-drivers/xf86-video-amdgpu-25.0.0-r1
* x11-drivers/xf86-video-ati-22.0.0
* sys-kernel/gentoo-sources-6.18.5
* KDE and Plasma packages are either version 6.22.0 or 6.5.5. I CBA to get a complete list, as there are so many relevant packages.
Yeah. I'm actually quite interested in hearing what "workarounds" and/or misbehavior you're talking about. 'amdgpu(4)' says this about the TearFree property:
Option "TearFree" "boolean"
Set the default value of the per-output ’TearFree’ property,
which controls tearing prevention using the hardware page flip‐
ping mechanism. TearFree is on for any CRTC associated with one
or more outputs with TearFree on. Two separate scanout buffers
need to be allocated for each CRTC with TearFree on. If this op‐
tion is set, the default value of the property is ’on’ or ’off’
accordingly. If this option isn’t set, the default value of the
property is auto, which means that TearFree is on for rotated
outputs, outputs with RandR transforms applied, for RandR 1.4
secondary outputs, and if ’VariableRefresh’ is enabled, otherwise
it’s off.
I think this is ultimately correct. The compositor will have to render a frame at some point after the VBlank signal, and it will need to render with it the buffers on-screen as of that point, which will be from whatever was last rendered to them.
This can be somewhat alleviated, though. Both KDE and GNOME have been getting progressively more aggressive about "unredirecting" surfaces into hardware accelerated DRM planes in more circumstances. In this situation, the unredirected planes will not suffer compositing latency, as their buffers will be scanned out by the GPU at scanout time with the rest of the composited result. In modern Wayland, this is accomplished via both underlays and overlays.
There is also a slight penalty to the latency of mouse cursor movement that is imparted by using atomic DRM commits. Since using atomic DRM is very common in modern Wayland, it is normal for the cursor to have at least a fraction of a frame of added latency (depending on many factors.)
I'm of two minds about this. One, obviously it's sad. The old hardware worked perfectly and never had latency issues like this. Could it be possible to implement Wayland without full compositing? Maybe, actually. But I don't expect anyone to try, because let's face it, people have simply accepted that we now live with slightly more latency on the desktop. But then again, "old" hardware is now hardware that can more often than not, handle high refresh rates pretty well on desktop. An on-average increase of half a frame of latency is pretty bad with 60 Hz: it's, what, 8.3ms? But half a frame at 144 Hz is much less at somewhere around 3.5ms of added latency, which I think is more acceptable. Combined with aggressive underlay/overlay usage and dynamic triple buffering, I think this makes the compositing experience an acceptable tradeoff.
What about computers that really can't handle something like 144 Hz or higher output? Well, tough call. I mean, I have some fairly old computers that can definitely handle at least 100 Hz very well on desktop. I'm talking Pentium 4 machines with old GeForce cards. Linux is certainly happy to go older (though the baseline has been inching up there; I think you need at least Pentium now?) but I do think there is a point where you cross a line where asking for things to work well is just too much. At that point, it's not a matter of asking developers to not waste resources for no reason, but asking them to optimize not just for reasonably recent machines but also to optimize for machines from 30 years ago. At a certain point it does feel like we have to let it go, not because the computers are necessarily completely obsolete, but because the range of machines to support is too wide.
Obviously, though, simply going for higher refresh rates can't fix everything. Plenty of laptops have screens that can't go above 60 Hz, and they are forever stuck with a few extra milliseconds of latency when using a compositor. It is unideal, but what are you going to do? Compositors offer many advantages, it seems straightforward to design for a future where they are always on.
I’m always a little bewildered by frame rate discussions. Yes, I understand that more is better, but for non-gaming apps (e.g. “productivity” apps), do we really need much more than 60 Hz? Yes, you can get smoother fast scrolling with higher frame rate at 120 Hz or more, but how many people were complaining about that over the last decade?
Even phones have moved in this direction, and it's immediately noticable when using it for the first time.
I'm now on 240hz and the effect is very diminished, especially outside of gaming. But even then I notice it, although stepping down to 144 isn't the worst. 60, though, feels like ice on your teeth.
60Hz is actually a downgrade from what people were used to. Sure, games and such struggled to get that kind of performance, but CRT screens did 75Hz/85Hz/100Hz quite well (perhaps at lower resolutions, because full-res 1200p sometimes made text difficult to read on a 21 inch CRT, with little benefit from the added smoothness as CRTs have a natural fuzzy edge around their straight lines anyway).
There's nothing about programming or word processing that requires more than maybe 5 or 6 fps (very few people type more than 300 characters per minute anyway) but I feel much better working on a 60 fps screen than I do a 30 fps one.
Everyone has different preferences, though. You can extend your laptop's battery life by quite a bit by reducing the refresh rate to 30Hz. If you're someone who doesn't really mind the frame rate of their computer, it may be worth trying!
When rendering a full frame at once and then displaying it, a modern screen is not only able to be more consistent in timing, it might be able to display the full frame faster than a CRT. Let's say 60Hz, and the frame is rendered just in time to start displaying. A CRT will take 16 milliseconds to do scanout. But if you get a screen that supports Quick Frame Transport, it might send over the frame data in only 3 milliseconds, and have the entire thing displayed by millisecond 4.
Quite a few. These articles tend to make the rounds when it comes up: https://danluu.com/input-lag/ https://lwn.net/Articles/751763/ Perception varies from person to person, but going from my 144hz monitor to my old 60hz work laptop is so noticeable to me that I switched it from a composited wayland DE to an X11 WM.
However, I do think that high refresh rates feel very nice to use even if they are not strictly necessary. I consider it a nice luxury.
I dunno. It does seem a bit odd, because who was thinking about the framerates of, like, desktops running productivity software, for the last couple decades? I guess I assumed this would never be a problem.
There are two things that typically impact mouse cursor latency, especially with regards to Wayland:
- Software-rendering, which is sometimes used if hardware cursors are unavailable or buggy for driver/GPU reasons. In this case the cursor will be rendered onto the composited desktop frame and thus suffer compositor latency, which is tied to refresh rate.
- Atomic DRM commits. Using atomic DRM commits, even the hardware-rendered cursors can suffer additional latency. In this case, the added latency is not necessarily tied to frame times or refresh rates. Instead, its tied to when during the refresh cycle the atomic commit is sent; specifically, how close to the deadline. I think in most cases we're talking a couple milliseconds of latency. It has been measured before, but I cannot find the source.
Wayland compositors tend to use atomic DRM commits, hence a slightly more laggy mouse cursor. I honestly couldn't tell you if there is a specific reason why they must use atomic DRM, because I don't have knowledge that runs that deep, only that they seem to.
A new display is usually going to be cheaper than a new computer. Displays which can actually deliver 240 Hz refresh rates can be had for under $200 on the lower end, whereas you can find 180 Hz displays for under $100, brand new. It's cheap enough that I don't think it's even terribly common to buy/sell the lower end ones second-hand.
For laptops, well, there is no great solution there; older laptops with 60 Hz panels are stuck with worse latency when using a compositor.
They aren't as common now, but when making a list of screens to replace my current one, I am limiting myself to IPS panels and quite a few of the modern options are still 60hz.
Of course, this isn't a huge deal to me. The additional latency is not an unusable nightmare. I'm just saying that if you are particularly latency sensitive, it's something that you can affordably mitigate even when using a compositor. I think most people have been totally fine eating the compositor latency at 60 Hz.
well, the answer is just no, wayland has been consistently slower than X11 and nothing running on top can't really go around that
Wayland is a specification, it has an inability to be "faster" than other options. That's like saying JSON is 5% slower than Word.
And as for the implementations being slower than X, that also doesn't reflect reality.
It's specifically about cursor lag, but I think that's because it's more difficult to experimentally measure app rendering latency.
No, they don't. I don't think Wayland ever supported exclusive fullscreen, MacOS doesn't, and Windows killed it a while back as well (in a Windows 10 update like 5-ish years ago?)
Jitter is a non-issue for things you want vsync'd (like every UI), and for games the modern solution is gsync/freesync which is significantly better than tearing.
Isn't that true for even the most basic features you expect from a windowing system? X11 may have come with everything and the kitchen sink, Wayland drops all that fun on the implementations.
GNOME does unredirect on Wayland since 2019: https://www.reddit.com/r/linux/comments/g2g99z/wayland_surfa...
> Windows killed it
They replaced it with "Fullscreen Optimisations", which is mostly the same, but more flexible as leaves detection of fullscreen exclusive windows to the window manager.
https://devblogs.microsoft.com/directx/demystifying-full-scr...
As far as I can find the update removed the option to turn this of.
Window's actual exclusive fullscreen always caused tons of issues with Alt+TAB because it was designed for a time when you couldn't fit both a game and the desktop in VRAM.
Yeah, it avoids doing the compositing part of being a compositor. It bypasses the entire pipeline.
[*] Well, there was an extension (can't recall the name right now) but not much used it and support was dropped at some point.
> I wonder how strictly they interpret behavior here given the architectural divergence?
It's right there in the rest of the sentence (that you didn't quote all of): "... or as much as possible considering the differences between X11 and Wayland."
I'll do my best. It won't be exactly the same, of course, but it will be as close as I can get it.
> As an example, focus-stealing prevention.
Focus stealing prevention is a place where I think xfwl4 could be at an advantage over xfwm4. Xfwm4 does a great job at focus-stealing prevention, but it has to work on a bunch of heuristics, and sometimes it just does the wrong thing, and there's not much we can do about it. Wayland's model plus xdg-activation should at least make the focus-or-don't-focus decision much more consistent.
> I am curious about the mandatory compositing overhead. Can the compositor replicate the input-to-pixel latency of uncomposited x11 on low-end devices or is that a class of performance we just have to sacrifice for the frame-perfect rendering of wayland?
I'm not sure yet, but I suspect your fears are well-founded here. On modern (and even not-so-modern) hardware, even low-end GPUs should be fine with all this (on my four-year-old laptop with Intel graphics, I can't tell the difference performance-wise with xfwm4's compositor on or off). But I know people run Xfce/X11 on very-not-modern hardware, and those people may unfortunately be left behind. But we'll see.
The compositing tax is just waiting for vsync; unless your machine is, like, a Pentium Classic, compositing itself isn't a problem.
Not that that's necessarily the best way to do it but nothing stops xfwl4 from simply granting every focus request and then applying their existing heuristics on the result of that.
I wonder how strictly they interpret behavior here given the architectural divergence?
As an example, focus-stealing prevention. In xfwm4 (and x11 generally), this requires complex heuristics and timestamp checks because x11 clients are powerful and can aggressively grab focus. In wayland, the compositor is the sole arbiter of focus, hence clients can't steal it, they can only request it via xdg-activation. Porting the legacy x11 logic involves the challenge of actually designing a new policy that feels like the old heuristic but operates on wayland's strict authority model.
This leads to my main curiosity regarding the raw responsiveness of xfce. On potato hardware, xfwm4 often feels snappy because it can run as a distinct stacking window manager with the compositor disabled. Wayland, by definition forces compositing. While I am not concerned about rust vs C latency (since smithay compiles to machine code without a GC), I am curious about the mandatory compositing overhead. Can the compositor replicate the input-to-pixel latency of uncomposited x11 on low-end devices or is that a class of performance we just have to sacrifice for the frame-perfect rendering of wayland?