2015 mbp 13" retina scaling lag on 4K monitor

[red-5]

This is an issue with high sierra and there is a large thread here:
https://forums.macrumors.com/threads/any-news-about-the-macbook-pro-nvidia-gpu-lag-yet.2088300/

 

[imp3rator]

Now add a second screen into that equation (after all, every Retina MBP has an internal screen that most likely is also running at a non-Default scaled resolution) and it adds up.

Do you say that Macbook "render" some graphics for internal display even in clamshell mode ?

 

[Christopher Kim]

Old thread, but I'm sure he meant assuming you have the laptop display open as well, not in closed-clamshell.

FWIW, I have the same monitor as OP (27" LG 4K UD68) and running scaled at "Looks like 2560 x 1440" at 60hz using my 2016 13" MBP, so only one generation Intel chip newer than the OP's 2015 13" MBP.

It looks fine for my purposes, but even I notice a little bit of screen lag when I'm moving around windows, or scrolling in content-heavy websites. And I echo earlier posts that this is due to macOS scaling, where whatever effective resolution (in my case 1440p) is "quadrupled" or "pixel-doubled" (to be 5K 5120 x 2880), and then that image is "downscaled" to show on my 4K 3840 x 2160 display. It looks beautiful to my eyes, but that beauty comes at the cost of greater GPU usage to run the scaled resolution.

 

[Romahaaa]

Ran into this thread for the same reasons involving a mid-2014 MBP and AOC U2879VF. I didn't see the slow-up much until High-Sierra. It's unfortunate, but the only "solution" seems to be switching to 1920x1080 scaled which results into ridiculously large GUI elements or native res, which results in ridiculously tiny GUI elements. C'mon Apple. The mid-2014 retina pros went through years of issues due to buggy problems running YouTube on Safari (didn't even work right out of the box)...only to be hampered by new issues with High-Sierra.

Oh buddy, how I understand you. That is such a disappointing what makes me think to migrate from MacbookPro 2015 15" top configuration to any other Windows laptop.
The only solutions I see are:
1. keep it on "Default" 1080p
2. buy a 5K monitor spending insane amount of $, and actually is easier to buy a new laptop
3. migrate to Windows