OPTIMIZE_LAUNCH=1 - why is this off by default? Should I use it?

[mcarans]

OPTIMIZE_LAUNCH=1 - Speeds up AppImage launch time using a DWARFS profile image (default: disabled). This is very similar to PGO optimizations in compilers. You often do not need to enable this, since DWARFS on its own is many times faster than SquashFS. In many cases, launch times are near-identical to those of native applications (±300 ms on a system with a 2016 CPU).

@Samueru-sama The docs have the above description. Is there a disadvantage to OPTIMIZE_LAUNCH=1? Are there some requirements that must be fulfilled to activate it? Is it very slow during appimage construction? Why wouldn't I want to turn it on?

[Samueru-sama]

In order to use OPTIMIZE_LAUNCH the system must have the container image mounted with FUSE support: https://github.com/pkgforge-dev/CollaboraOffice-AppImage/blob/a9a36b3ddcbb7e773d9e428cd885d0edefd32a55/.github/workflows/appimage.yml#L24-L26

That alone is a big issue that prevents us from enabling this by default always.

Another thing is that OPTIMIZE_LAUNCH is rarely needed, DwarFS alone is very fast already on its own. Where this option helps a lot is on very big applications (appimages bigger than 250 MiB) or appimages that read over 100 files on startup (GIMP).

For the average appimage that is less than 100 MiB, using OPTIMIZE_LAUNCH will only save you 150ms at best in the launch time.

[Samueru-sama]

For applications like terminal emulators, text editors, web browsers, etc (basically stuff you open and close often) you want to use URUNTIME_PRELOAD=1 instead.

This guarantees an instantaneous launch speed, since the appimage leaves the filesystem mounted always.

[mcarans]

@Samueru-sama Oolite is 248Mb. I can add FUSE support (I needed it before with the traditional appimage). Since the game is just under your suggested size, will the benefit be worth it?

[Samueru-sama]

@Samueru-sama Oolite is 248Mb. I can add FUSE support (I needed it before with the traditional appimage). Since the game is just under your suggested size, will the benefit be worth it?

Don't think so:

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• A cold launch (dropping all caches) it takes 1 second to launch the appimage. This is on a CPU from 2016 btw

• Afterwards, it takes ~500ms to launch, since a lot of stuff is already cached.

• For reference, a cold launch of the appimage extracted takes ~500ms, and after that it only goes down to ~475ms. That is as low as it can go.

So basically if you use OPTIMIZE_LAUNCH you will only save about 400 ms on the very very first launch of the game.

[mcarans]

So basically if you use OPTIMIZE_LAUNCH you will only save about 400 ms on the very very first launch of the game.

Great, thanks for checking!