Optimizing Nuke

Nuke's defaults come from benchmarks, so the gains are almost always in how the app asks for images, and rarely in its configuration. A 12 MP photo decoded for a 120-point cell costs 46 MB, and no setting makes up for that.

Measure first, change one thing, and measure again. Each change here has a cost, and some make things worse when the cause is something else. If you can't run the app, say that what you changed comes from reading the code, and that it's unmeasured. For the API in general, see llms-full.txt at the root of the package.

Measure

Launch with NUKE_DIAGNOSTICS_LOG=1, in the scheme or like this, and read one line per task:

SIMCTL_CHILD_NUKE_DIAGNOSTICS_LOG=1 xcrun simctl launch booted <bundle-id>
xcrun simctl spawn booted log stream --predicate 'subsystem == "com.github.kean.Nuke.ImagePipeline"'

ImageTask #1 · success · 78.5 ms · from network · https://example.com/a.png · 1200×800 · png · 3.7 MB in memory · 70 KB

Go through the slow screen twice: once on a fresh install, and again after relaunching.

In the log	It means	Go to
from network after a relaunch	The disk cache missed	Cache keys, Disk cache
from httpCache, and tens of ms	URLCache asked the server whether the image changed	Disk cache
MB in memory over width × height × 4 of the cell, in pixels	The image is bigger than what's displayed	Decode less
The same URL twice, with no coalesced	Two requests that differ, so nothing is shared	Cache keys, Prefetching
More lines than cells on screen, on open	Everything loads at once	Load only what's on screen
A long list of cancelled	Normal while scrolling fast: the cells cancel the loads they scrolled past	Nothing

For where the time of a slow task went: