examples(allocation): free memory after unmarshalling a result from the guest

[lburgazzoli]

This is a follow up PR to amend tinygo's allocation example according to knqyf263/go-plugin#45

[codefromthecrypt]

looks good. can you sweep the docs, the tinygo one in site/ and also this one's README to make sure there are no other notes/code that are similar and need an update?

[lburgazzoli]

sure thing!

It will take a while as I'm travelling this week

[codefromthecrypt]

cool. for now this can merge anyway. more commits aren't a problem!

[codefromthecrypt]

I reverted this as it caused a large performance regression. We should probably add benchmark tests to tinymem to ensure we don't accidentally change the performance profile without knowing it. Maybe we can find a way to explain why the difference is so large.

# without this commit
$ go test -run='^$' -bench '^BenchmarkAllocation.*' ./internal/integration_test/vs/compiler ./internal/integration_test/vs/interpreter -count=6 > old.txt
# with this commit
$ go test -run='^$' -bench '^BenchmarkAllocation.*' ./internal/integration_test/vs/compiler ./internal/integration_test/vs/interpreter -count=6 > new.txt
$ benchstat old.txt new.txt 
goos: darwin
goarch: arm64
pkg: github.com/tetratelabs/wazero/internal/integration_test/vs/compiler
                          │   old.txt   │                new.txt                │
                          │   sec/op    │    sec/op     vs base                 │
Allocation/Compile-12       3.705m ± 7%    3.647m ± 2%          ~ (p=0.132 n=6)
Allocation/Instantiate-12   303.9µ ± 2%    292.3µ ± 1%     -3.83% (p=0.002 n=6)
Allocation/Call-12          1.571µ ± 2%   28.759µ ± 3%  +1731.20% (p=0.002 n=6)
geomean                     120.9µ         313.0µ        +158.81%

                          │   old.txt    │                new.txt                │
                          │     B/op     │     B/op      vs base                 │
Allocation/Compile-12       2.125Mi ± 0%   2.124Mi ± 0%     -0.05% (p=0.002 n=6)
Allocation/Instantiate-12   314.6Ki ± 0%   314.6Ki ± 0%          ~ (p=0.331 n=6)
Allocation/Call-12            48.00 ± 0%    735.00 ± 2%  +1431.25% (p=0.002 n=6)
geomean                     31.77Ki        78.89Ki        +148.28%

                          │   old.txt   │               new.txt               │
                          │  allocs/op  │  allocs/op   vs base                │
Allocation/Compile-12       1.852k ± 0%   1.854k ± 0%  +0.11% (p=0.002 n=6)
Allocation/Instantiate-12    802.0 ± 0%    802.0 ± 0%       ~ (p=1.000 n=6) ¹
Allocation/Call-12           5.000 ± 0%    5.000 ± 0%       ~ (p=1.000 n=6) ¹
geomean                      195.1         195.2       +0.04%
¹ all samples are equal

pkg: github.com/tetratelabs/wazero/internal/integration_test/vs/interpreter
                          │   old.txt   │               new.txt               │
                          │   sec/op    │   sec/op     vs base                │
Allocation/Compile-12       1.144m ± 0%   1.147m ± 1%         ~ (p=0.240 n=6)
Allocation/Instantiate-12   90.26µ ± 0%   91.45µ ± 1%    +1.31% (p=0.002 n=6)
Allocation/Call-12          28.65µ ± 1%   67.66µ ± 2%  +136.15% (p=0.002 n=6)
geomean                     143.6µ        192.2µ        +33.86%

                          │   old.txt    │               new.txt                │
                          │     B/op     │     B/op      vs base                │
Allocation/Compile-12       1.449Mi ± 0%   1.449Mi ± 0%         ~ (p=0.290 n=6)
Allocation/Instantiate-12   222.7Ki ± 0%   222.7Ki ± 0%         ~ (p=0.723 n=6)
Allocation/Call-12          2.254Ki ± 0%   7.155Ki ± 1%  +217.39% (p=0.002 n=6)
geomean                     90.65Ki        133.2Ki        +46.96%

                          │   old.txt   │                new.txt                │
                          │  allocs/op  │  allocs/op   vs base                  │
Allocation/Compile-12       1.071k ± 0%   1.074k ± 0%    +0.28% (p=0.002 n=6)
Allocation/Instantiate-12    747.0 ± 0%    747.0 ± 0%         ~ (p=1.000 n=6) ¹
Allocation/Call-12           99.00 ± 0%   286.50 ± 1%  +189.39% (p=0.002 n=6)
geomean                      429.5         612.6        +42.64%
¹ all samples are equal

[codefromthecrypt]

Hi, can you try this PR again, except make sure the benchmark host code is updated the same way as the example host code was? Maybe this is why the regression happened https://github.com/tetratelabs/wazero/blob/main/internal/integration_test/vs/bench_allocation.go

[lburgazzoli]

@codefromthecrypt #1390