Prior to this commit, `MemoryStore::DupCoder` called `Entry#dup_value!`
in both `dump` and `load` to guard against external mutation of cached
values. `Entry#dup_value!` calls `Marshal.dump` then `Marshal.load` to
dup complex objects. However, to prevent external mutation, we only
need to call `Marshal.dump` once for `DupCoder.dump` and `Marshal.load`
once for `DupCoder.load`.
This commit changes `DupCoder` to call `Marshal.dump` and `Marshal.load`
directly instead of relying on `Entry#dup_value!`, thus halving the work
done by `Marshal` when writing and reading complex objects.
__Benchmark__
```ruby
# frozen_string_literal: true
require "benchmark/ips"
require "active_support"
require "active_support/cache"
LARGE_OBJECT = 100.times.map { "x" * 100 }
LARGE_STRING = LARGE_OBJECT.join
cache = ActiveSupport::Cache.lookup_store(:memory_store)
Benchmark.ips do |x|
x.report("large string") do
cache.write("x", LARGE_STRING)
cache.read("x")
end
x.report("large object") do
cache.write("x", LARGE_OBJECT)
cache.read("x")
end
end
```
__Before__
```
Warming up --------------------------------------
large string 2.667k i/100ms
large object 332.000 i/100ms
Calculating -------------------------------------
large string 26.539k (± 1.8%) i/s - 133.350k in 5.026373s
large object 3.336k (± 0.9%) i/s - 16.932k in 5.076458s
```
__After__
```
Warming up --------------------------------------
large string 2.541k i/100ms
large object 715.000 i/100ms
Calculating -------------------------------------
large string 25.117k (± 1.7%) i/s - 127.050k in 5.059945s
large object 7.111k (± 1.2%) i/s - 35.750k in 5.028267s
```
Closes#46403.
Co-authored-by: Breno Gazzola <breno.gazzola@gmail.com>
Co-authored-by: Jean Boussier <jean.boussier@gmail.com>
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