[Koiwai]

It's actually the opposite, modern mode uses gpu for compositing, classic modes uses cpu, and any gpu would beat cpu handily in that task including integrated ones.

Unless, you didn't install the correct driver and used standard vga driver, or like in a vm which doesn't provide gpu acceleration.

[badsectoracula]

The parent post refers to responsiveness, not throughput. Even if the GDI was fully accelerated, the compositor adds additional input lag because it has to sync with the monitor's refresh rate whereas without DWM the monitor displays whetever is on the framebuffer. The drawback is that you get tearing and damage artifacts (like the classic crash window[0]).

[0] https://mrdoob.com/lab/javascript/effects/ie6/

[andai]

Not sure if this is exactly related, since it's beyond my understanding, but it seems game devs have been struggling to get things drawn on the screen at the expected time. (The speaker says things were much more straightforward on the Amiga. Progress works in funny ways!)

https://www.youtube.com/watch?v=n0zT8YSSFzw

[incrudible]

Classic mode does not use compositing at all, but the drawing routines of GDI etc were hardware accelerated already. Keeping a buffer around for every window for compositing could become a big performance problem and was part of the reason why Vista was considered slow. Mac OS X had this problem too.

[rootw0rm]

I was curious myself, this link is a bit of an introduction to the mess:

https://learn.microsoft.com/en-us/windows/win32/direct2d/com...

"GDI is hardware accelerated on Windows XP, and accelerated on Windows 7 when the Desktop Window Manager is running and a WDDM 1.1 driver is in use. Direct2D is hardware accelerated on almost any WDDM driver and whether or not DWM is in use. On Vista, GDI will always render on the CPU."

[winrid]

GPU doesn't nessisarily mean less lag depending on buffers and implementation.

[asveikau]

I know this. Heard it a bunch. The composited path was still slower.

[Koiwai]

Well, my experience was modern mode is way more responsive, and I've convinced at least 5 friends on sight.

[andai]

I've spent the last few days messing with Linux in both VirtualBox and VMWare and I found that disabling 3D acceleration leads to ~2x faster boot, and disabling desktop compositing (in the Linux guest) leads to 5x less lag when moving things around on screen.

I was surprised, because I thought using 3D acceleration and compositing would be faster.

Also, I run the VM at half res and used DPI workaround (.manifest file) to let Windows scale the VM instead of VirtualBox (VirtualBox scaling is very slow for some reason).

[Filligree]

Linux in a VM doesn’t behave like Linux on bare hardware, and graphics acceleration in particular is a house of cards. You can’t draw any real conclusions from this.