[ruby-core:69215] [Ruby trunk - Feature #11158] Introduce a Symbol.count API as a more efficient alternative to Symbol.all_symbols.size

Issue #11158 has been updated by Nobuyoshi Nakada.


Lourens Naud辿 wrote:
> Please let me know if this is inline with an expected core API, anything I could clean up further and if there's any possibility of such a change also being backported to 2.1 as well? (happy to create a new patch for 2.1)

New features are never backported to 2.2 or earlier.


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Feature #11158: Introduce a Symbol.count API as a more efficient alternative to Symbol.all_symbols.size
https://bugs.ruby-lang.org/issues/11158#change-52467

* Author: Lourens Naud辿
* Status: Open
* Priority: Normal
* Assignee: 
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We're in the process of migrating a very large Rails codebase from a Ruby 2.1.6 runtime to Ruby 2.2.2 and as part of this migration process would like to keep track of Symbol counts and Symbol GC efficiency in our metrics system. Preferably still while on 2.1 (however this implies a backport to 2.1 as well), but would definitely be useful in 2.2 as well.

Currently the recommended and only reliable way to get to the Symbol counts is via Symbol.all_symbols.size, which:

* Allocates an Array
* rb_ary_push and walking the symbol table isn't exactly efficient

Here's some benchmarks:

~~~
./miniruby -Ilib -rbenchmark -e "p Benchmark.measure { 10_000.times{ Symbol.count } }"
#<Benchmark::Tms:0x007f8bc208bdd0 @label="", @real=0.0011274919961579144, @cstime=0.0, @cutime=0.0, @stime=0.0, @utime=0.01, @total=0.01>
~~~

~~~
./miniruby -Ilib -rbenchmark -e "p Benchmark.measure { 10_000.times{ Symbol.all_symbols.size } }"
#<Benchmark::Tms:0x007fa47205a550 @label="", @real=0.3135859479953069, @cstime=0.0, @cutime=0.0, @stime=0.03, @utime=0.29, @total=0.31999999999999995>
~~~

I implemented and attached a patch for a simple Symbol.count API that just returns a numeric version of the symbol table size, without having to do any iteration.

Please let me know if this is inline with an expected core API, anything I could clean up further and if there's any possibility of such a change also being backported to 2.1 as well? (happy to create a new patch for 2.1)

---Files--------------------------------
symbol_count.patch (4.4 KB)


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