[ruby-core:98463] [Ruby master Bug#16900] Disposable call-cache introduced memory leak
From:
merch-redmine@...
Date:
2020-05-20 23:08:43 UTC
List:
ruby-core #98463
Issue #16900 has been updated by jeremyevans0 (Jeremy Evans).
Using the following program, I have determined that Ruby isn't leaking objects according to `ObjectSpace.count_objects`, so it is probably leaking some other memory.
```ruby
module M; def bar; end; end
h = nil
h2 = ObjectSpace.count_objects
require 'objspace'
100.times { |i|
10000.times {
Class.new do
def foo; end
include M
end
}
GC.start
h = h2
h2 = ObjectSpace.count_objects
h2.each do |k,v|
p [i, k, v, h[k]] if h[k] != v
end
GC.start
}
```
Output from the program:
```
[0, :TOTAL, 10601, 9786]
[0, :FREE, 4874, 1823]
[0, :T_CLASS, 440, 436]
[0, :T_STRING, 2420, 4506]
[0, :T_ARRAY, 112, 259]
[0, :T_HASH, 5, 7]
[0, :T_DATA, 111, 128]
[0, :T_IMEMO, 2565, 2554]
[0, :T_ICLASS, 27, 26]
[1, :FREE, 4866, 4874]
[1, :T_HASH, 8, 5]
[1, :T_DATA, 112, 111]
[1, :T_IMEMO, 2569, 2565]
[2, :FREE, 4865, 4866]
[2, :T_HASH, 9, 8]
```
This shows that after the 3rd iteration, object counts remain the same.
----------------------------------------
Bug #16900: Disposable call-cache introduced memory leak
https://bugs.ruby-lang.org/issues/16900#change-85737
* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Backport: 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED
----------------------------------------
commit:b9007b6c548f91e88fd3f2ffa23de740431fa969 (Introduce disposable call-cache) introduced a memory leak for classes that include or prepend modules. Taking the example memory leak script used in the commit message for commit:5922c954614e5947a548780bb3b894626affe6dd:
```ruby
module M; def bar; end; end
loop{
Class.new do
def foo; end
prepend M
end
}
```
There is unbounded growth:
```
jeremy 56984 0.0 0.1 59540 14940 p2 S+ 5:15PM 0:00.19 ruby example.rb
jeremy 56984 0.0 0.1 61852 18640 p2 S+ 5:15PM 0:00.40 ruby example.rb
jeremy 56984 0.0 0.1 62700 19940 p2 S+ 5:15PM 0:00.62 ruby example.rb
jeremy 56984 0.0 0.1 63696 21364 p2 S+ 5:15PM 0:00.83 ruby example.rb
jeremy 56984 4.1 0.1 64632 22748 p2 S+ 5:15PM 0:01.05 ruby example.rb
jeremy 56984 4.1 0.1 65664 24188 p2 S+ 5:15PM 0:01.26 ruby example.rb
jeremy 56984 4.1 0.2 66632 25432 p2 S+ 5:15PM 0:01.47 ruby example.rb
jeremy 56984 4.1 0.2 67484 26552 p2 S+ 5:15PM 0:01.70 ruby example.rb
jeremy 56984 8.5 0.2 68456 27772 p2 S+ 5:15PM 0:01.92 ruby example.rb
jeremy 56984 8.5 0.2 69536 29164 p2 S+ 5:15PM 0:02.14 ruby example.rb
jeremy 56984 8.5 0.2 70424 30252 p2 S+ 5:15PM 0:02.36 ruby example.rb
```
This issue appears to be limited to classes that include or prepend modules.
* Same memory leak when switching from `prepend` to `include`
* No memory leak when switching from `Class.new` to `Module.new`
* No memory leak when removing the `prepend`
* No memory leak when removing the `prepend` and subclassing the class.
--
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