[ruby-core:95268] [Ruby master Feature#16245] Add interfaces to count and measure size all IMEMO objects

[sam.saffron@gmail.com]

Issue #16245 has been updated by sam.saffron (Sam Saffron).


An alternative design could be to add 1 extra object to the heap

RubyVM::NonMaterializedInstructionSequence

Then `each_object` could include it and we could use that to measure size of all IMEMOs that are not materialized yet. Advantage here is that naive `memsize_of` all objects will return all the memory. 

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Feature #16245: Add interfaces to count and measure size all IMEMO objects
https://bugs.ruby-lang.org/issues/16245#change-81944

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Koichi introduced an experimental gem: https://github.com/ko1/iseq_collector

It allows:

ObjectSpace.each_iseq{|iseq| ...}
ObjectSpace.count_iseq #=> Integer
ObjectSpace.memsize_of_all_iseq (should not generate RubyVM::InstructionSequence wrappers for IMEMOs)

Since the wrapper object  RubyVM::InstructionSequence is lazily allocated, ObjectSpace.each_object does not find these IMEMOs unless they have been wrapped. This design is good and conserves memory. 

`count_iseq` and `memsize_of_all_iseq` are very powerful metrics most large Ruby deployments can use to automatically detect method leaks introduced via meta programming. These issues are invisible now short of walking a heap dump. 

Can we add the new interface into 2.7?



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