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# Description
This is another easy performance lift that just changes `env_vars` and
`env_hidden` on `Stack` to use `Arc`. I noticed that these were being
cloned on essentially every closure invocation during captures
gathering, so we're paying the cost for all of that even when we don't
change anything. On top of that, for `env_vars`, there's actually an
entirely fresh `HashMap` created for each child scope, so it's highly
unlikely that we'll modify the parent ones.
Uses `Arc::make_mut` instead to take care of things when we need to
mutate something, and most of the time nothing has to be cloned at all.
# Benchmarks
The benefits are greater the more calls there are to env-cloning
functions like `captures_to_stack()`. Calling custom commands in a loop
is basically best case for a performance improvement. Plain `each` with
a literal block isn't so badly affected because the stack is set up
once.
## random_bytes.nu
```nushell
use std bench
do {
const SCRIPT = ../nu_scripts/benchmarks/random-bytes.nu
let before_change = bench { nu $SCRIPT }
let after_change = bench { target/release/nu $SCRIPT }
{
before: ($before_change | reject times),
after: ($after_change | reject times)
}
}
```
```
╭────────┬──────────────────────────────╮
│ │ ╭──────┬───────────────────╮ │
│ before │ │ mean │ 603ms 759µs 727ns │ │
│ │ │ min │ 593ms 298µs 167ns │ │
│ │ │ max │ 648ms 612µs 291ns │ │
│ │ │ std │ 9ms 335µs 251ns │ │
│ │ ╰──────┴───────────────────╯ │
│ │ ╭──────┬───────────────────╮ │
│ after │ │ mean │ 518ms 400µs 557ns │ │
│ │ │ min │ 507ms 762µs 583ns │ │
│ │ │ max │ 566ms 695µs 166ns │ │
│ │ │ std │ 9ms 554µs 767ns │ │
│ │ ╰──────┴───────────────────╯ │
╰────────┴──────────────────────────────╯
```
## gradient_benchmark_no_check.nu
```nushell
use std bench
do {
const SCRIPT = ../nu_scripts/benchmarks/gradient_benchmark_no_check.nu
let before_change = bench { nu $SCRIPT }
let after_change = bench { target/release/nu $SCRIPT }
{
before: ($before_change | reject times),
after: ($after_change | reject times)
}
}
```
```
╭────────┬──────────────────────────────╮
│ │ ╭──────┬───────────────────╮ │
│ before │ │ mean │ 146ms 543µs 380ns │ │
│ │ │ min │ 142ms 416µs 166ns │ │
│ │ │ max │ 189ms 595µs │ │
│ │ │ std │ 7ms 140µs 342ns │ │
│ │ ╰──────┴───────────────────╯ │
│ │ ╭──────┬───────────────────╮ │
│ after │ │ mean │ 134ms 211µs 678ns │ │
│ │ │ min │ 132ms 433µs 125ns │ │
│ │ │ max │ 135ms 722µs 583ns │ │
│ │ │ std │ 793µs 134ns │ │
│ │ ╰──────┴───────────────────╯ │
╰────────┴──────────────────────────────╯
```
# User-Facing Changes
Better performance, particularly for custom commands, especially if
there are a lot of environment variables. Nothing else.
# Tests + Formatting
All passing.
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| .. | ||
| src | ||
| Cargo.toml | ||
| LICENSE | ||