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Desktop compositing latency is real

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Re: Desktop compositing latency is real

#71

Post by amaranth »

srcmap wrote: post #35

According to this: https://www.youtube.com/watch?v=BTURkjYJ_uk Firefox's servo engine can compose CSS elements/Display List together at 500 frames / second. Maybe next version of Windows / Linux desktop should use FF's servo engine?

Your application renders a frame then the compositor gets it and does its transformations, if any. The composited result is then rendered to the screen thus adding one frame of latency. That's why the article says one solution would be to get a 144Hz monitor, it would reduce the time between frames so an extra frame of latency wouldn't be as bad.

You could potentially reduce this delay as well by having the application and the compositor in communication. Since rendering is going to be synced to vblank if you can get the application to not try to sync as well and instead just notify the compositor when it is done drawing a frame you could potentially get the application drawing and the compositor drawing in the same vblank interval. This is what Wayland and DRI3 Present let you do in the Linux world, I assume Windows has something similar but you'd need to opt-in to it so I bet nothing uses it.

Re: Desktop compositing latency is real

#72

Post by igor_p »

Is there a website that demonstrates the effects of latency after pressing a key? I know there's examples of different frame rates shown with moving circles, but I don't think that's quite the same.

I mean is there really a noticeable difference between say 20 and 40 ms?

Re: Desktop compositing latency is real

#73

Post by _jal »

aduitsis wrote: post #32
ino wrote: post #29

Earlier quoted context omitted.

I have the same monitor and it's pretty good. The only thing I don't quite like is the pixel size, it's a bit small for native scaling. I kind of wish i had gone for the 27". I went with two 25" because two 27" were a bit too big for me.

P2715Q user here. One of the best monitors currently available, excellent color reproduction, top of the line quality. The 4K resolution however is a major problem when you are using Windows 7. Some applications will not play correctly when you try to scale up and at the end you get a mess. Windows 10 is better, but not perfect.

Ditto, have a pair of those. They are the nicest I've used in a long time. Haven't noticed the Windows issues, but then I only run a couple applications under win in a VM. No issues with Linux.

They've released the UP2718Q at a serious price difference. I'd like to see one in person, but a 3x price increase requires a lot of improvement over an already great monitor.

Re: Desktop compositing latency is real

#74

Post by 542458 »

dilap wrote: post #68
em3rgent0rdr wrote: post #48

Earlier quoted context omitted.

this reminds me of the argument that instead of going to USB C 3.1 as the grand unifying connector for all peripherals (including video), we should have instead migrated to Ethernet cables for everything.

in all seriousness, why not?

The obvious ones: Ethernet cables are big (imagine one on a phone), and aren't designed to be plugged and unplugged the massive number of times that USB cables are (spring contacts wear out, little clips break).

Re: Desktop compositing latency is real

#76

Post by lmm »

dilap wrote: post #68
em3rgent0rdr wrote: post #48

Earlier quoted context omitted.

this reminds me of the argument that instead of going to USB C 3.1 as the grand unifying connector for all peripherals (including video), we should have instead migrated to Ethernet cables for everything.

in all seriousness, why not?

The little plastic bits always snap off. Ethernet is great for semipermanent wires but not very good for peripherals like portable hard drives that are constantly disconnected and reconnected.

Re: Desktop compositing latency is real

#77

Post by tauio111 »

I always thought I was the only one noticing this. With Compositing enabled, both with DWM and on GNU/Linux, the whole interaction seems to become "soft" instead of the raw that feels much nicer and snappy. From my experience it also has to do with passing through the stack to the GPU when compositing, running it all from the CPU is what makes it feel snappy.

I've also been researching about removing the triple buffer vsync on W10. It seems it was possible in the first builds by replacing some system files, but that option is gone now with the recent big releases.

As of that, I do not see the real reason why compositing would be needed on W10, as transparency and etc arent important factors.

Re: Desktop compositing latency is real

#78

Post by stult »

wruza wrote: post #56
fredley wrote: post #37

Earlier quoted context omitted.

Layers of abstraction take you further away from the metal. The more layers of abstraction your keypress must traverse before rendering is complete and the photons have reached your retina, the longer it will be until that happens. Layers of abstraction make complex tasks more reachable by a larger number of programmers by reducing the amount of specialist knowledge about those lower layers required to do the job. Th…

Numerous games, including those having complex graphics and behavior, can render 120+ frames per second and realtime interactions (physics, optics, reactions) on pretty average hardware. I don’t think that game scripters who make final things like scenery or ui face complexity much harder than those in gtk/qt/wpf/htmljs widget programming. Details would be interesting though, since I’m no game developer. If true, it…

It's a lot easier to optimize the APIs underlying those scripts because there are far fewer of them in even the most complicated video games than there are comparable abstractions in modern OSs. And there's more motivation. People accept the slightly lower responsiveness in normal OS interactions whereas even millisecond delays in competitive games are intolerable.

Re: Desktop compositing latency is real

#79

Post by badsectoracula »

em3rgent0rdr wrote: post #45
Zardoz84 wrote: post #31

> Don’t you find it a bit funny that Windows 95 is actually snappier than Windows 10? It’s really a shame that response times in modern computers are visibly worse than those in twenty years ago. My Amiga A1200 (Only have extra RAM) feels faster and more responsive that any modern computer with Windows or GNU/Linux desktop.

> "or GNU/Linux desktop" I believe Wayland has made some latency improvements.

Wayland uses a composition model which is inherently slower than having direct access to the front buffer.

Re: Desktop compositing latency is real

#80

Post by nickjj »

aduitsis wrote: post #32
ino wrote: post #29

Earlier quoted context omitted.

I have the same monitor and it's pretty good. The only thing I don't quite like is the pixel size, it's a bit small for native scaling. I kind of wish i had gone for the 27". I went with two 25" because two 27" were a bit too big for me.

P2715Q user here. One of the best monitors currently available, excellent color reproduction, top of the line quality. The 4K resolution however is a major problem when you are using Windows 7. Some applications will not play correctly when you try to scale up and at the end you get a mess. Windows 10 is better, but not perfect.

I looked at 4k monitors but ultimately decided against it because as soon as you start scaling then you lose the extra screen real estate.

At 4k 150% scaling you end up with the same screen space as 2560x1440.

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