Reduce stack usage by boxing File in Dist, CachePolicy and large futures

[konstin]

This is #947 again but this time merging into main instead of downstack, sorry for the noise.

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Windows has a default stack size of 1MB, which makes puffin often fail with stack overflows. The PR reduces stack size by three changes:

• Boxing File in Dist, reducing the size from 496 to 240.
• Boxing the largest futures.
• Boxing CachePolicy

Method

Debugging happened on linux using #941 to limit the stack size to 1MB. Used ran the command below.

RUSTFLAGS=-Zprint-type-sizes cargo +nightly build -p puffin-cli -j 1 > type-sizes.txt && top-type-sizes -w -s -h 10 < type-sizes.txt > sizes.txt

The main drawback is top-type-sizes not saying what the __awaitee is, so it requires manually looking up with a future with matching size.

When the brotli features on reqwest is active, a lot of brotli types show up. Toggling this feature however seems to have no effect. I assume they are false positives since the brotli crate has elaborate control about allocation. The sizes are therefore shown with the feature off.

Results

The largest future goes from 12208B to 6416B, the largest type (PrioritizedDistribution, see also #948) from 17448B to 9264B. Full diff: https://gist.github.com/konstin/62635c0d12110a616a1b2bfcde21304f

For the second commit, i iteratively boxed the largest file until the tests passed, then with an 800KB stack limit looked through the backtrace of a failing test and added some more boxing.

Quick benchmarking showed no difference:

$ hyperfine --warmup 2 "target/profiling/main-dev resolve meine_stadt_transparent" "target/profiling/puffin-dev resolve meine_stadt_transparent" 
Benchmark 1: target/profiling/main-dev resolve meine_stadt_transparent
  Time (mean ± σ):      49.2 ms ±   3.0 ms    [User: 39.8 ms, System: 24.0 ms]
  Range (min … max):    46.6 ms …  63.0 ms    55 runs
 
  Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
 
Benchmark 2: target/profiling/puffin-dev resolve meine_stadt_transparent
  Time (mean ± σ):      47.4 ms ±   3.2 ms    [User: 41.3 ms, System: 20.6 ms]
  Range (min … max):    44.6 ms …  60.5 ms    62 runs
 
  Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
 
Summary
  target/profiling/puffin-dev resolve meine_stadt_transparent ran
    1.04 ± 0.09 times faster than target/profiling/main-dev resolve meine_stadt_transparent