Reduce allocations during resize with (setq frame-resize-pixelwise t) in your init!

[jdtsmith]

During resize, every 100ms (a rate which emacs itself may determine), a brand new pair of IOSurfaces are allocated (for the front and back frame buffer), at 5-50MB a pop. Pretty inefficient.

A better approach might be to limit the view of the IOSurface and resize it only to make it larger (at least during resize), with some increment like 25%, as needed. One complications is we also have old-school CGImage buffers and the new (optional) Metal buffers too, so they'd also need the same treatment. But could start with IOSurfaces. Once a given resize has completed (viewDidEndLiveResize) a "correct-size" frame buffer pair can be re-allocated.

[jdtsmith]

Update: @gerd-moellmann suggested enabling frame-resize-pixelwise in the init. Not only does this make resizing very smooth, it entirely eliminates all the allocations of IOSurface VM.

Instruments Allocations:

Each of the following is a report from Instruments "Allocation" run sorted by Total Bytes. Each is about 11s worth of rapid resizing of the sole frame, showing my init.el (this is the emacs-30 branch).

Without pixelwise

1	All Heap & Anonymous VM	73.84 MiB	255978	15901933	3.04 GiB	16157911	Ratio: %0.02, %0.98
0	All Heap Allocations	66.75 MiB	255973	15897266	687.54 MiB	16153239	Ratio: %0.02, %0.20
0	All Anonymous VM	7.09 MiB	5	4667	2.37 GiB	4672	Ratio: %0.00, %0.78
0	VM: IOSurface	7.00 MiB	2	214	2.29 GiB	216	Ratio: %0.00, %0.75

With pixelwise

1	All Heap & Anonymous VM	77.71 MiB	185970	429122	208.52 MiB	615092	Ratio: %0.37, %0.63
0	All Heap Allocations	63.26 MiB	185965	426177	126.61 MiB	612142	Ratio: %0.30, %0.30
0	All Anonymous VM	14.45 MiB	5	2945	81.91 MiB	2950	Ratio: %0.07, %0.32
0	VM: IOSurface	14.41 MiB	2	0	14.41 MiB	2	Ratio: %0.07, %0.00

Note in particular the last line in each: 2 persistent IOSurface allocations each (front/back frame buffer), but 214 temporary allocations totalling 2.3GB without pixelwise. I don't understand the reason for this difference, but I'll take it! Update: it doesn't redraw at all during resize until you release, but that's fine.

Recommendation

(setq frame-resize-pixelwise t)

in your init.el!

[jdtsmith]

On the other hand, frame-resize-pixelwise prevents redisplay (somehow) during pixel-precise resize. Maybe this limitation could still be lifted with conservative only-growing frame buffer allocation. Worth looking at.