perf(profiling): shrink the size of ZendFrame

[morrisonlevi]

PROF-9925

Description

Previously, each frame was 7 64 bits. They are now 3 64 bits, at the cost that there are slightly more String copies than before. This PR is an attempt to see if this trade-off is worth it.

The current status is that when things are fetched from cache, or if the inserting thing returns a borrowed Cow<str> such as for filenames, then we have the same number of copies as before. Function names are going to return an owned Cow<str>, though, and in this case we have an extra copy compared to before. The benchmarks that the PR bot posts do not capture this case.

Reviewer checklist

• [ ] Test coverage seems ok.
• [ ] Appropriate labels assigned.

[pr-commenter[bot]]

Benchmarks

Benchmark execution time: 2024-06-12 23:26:42

Comparing candidate commit a8fc7ffaf2c224eb36fa088733a718e3f1bada75 in PR branch levi/smaller-frames with baseline commit 9f4a6a50e8c487127431af623037a08d9dc1c2b1 in branch master.

Found 5 performance improvements and 0 performance regressions! Performance is the same for 24 metrics, 7 unstable metrics.

scenario:walk_stack/1

• 🟩 wall_time [-556.277ns; -528.070ns] or [-2.347%; -2.228%]

scenario:walk_stack/99

• 🟩 wall_time [-725.636ns; -696.953ns] or [-2.885%; -2.771%]

scenario:walk_stack_instructions/1

• 🟩 instructions [-6.2K instructions; -6.2K instructions] or [-5.991%; -5.980%]

scenario:walk_stack_instructions/50

• 🟩 instructions [-5.5K instructions; -5.4K instructions] or [-5.260%; -5.231%]

scenario:walk_stack_instructions/99

• 🟩 instructions [-4.3K instructions; -4.3K instructions] or [-4.142%; -4.114%]

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.40%. Comparing base (9f4a6a5) to head (a8fc7ff).

Additional details and impacted files

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