Issue #8985 has been reported by funny_falcon (Yura Sokolov).

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Feature #8985: xwillfree - promise to free memory
https://bugs.ruby-lang.org/issues/8985

Author: funny_falcon (Yura Sokolov)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: current: 2.1.0


This patch changes semantic of RUBY_GC_MALLOC_LIMIT.
Instead of being "periodical trigger" it becomes more like "safety trigger"
which fires in allocation increase (instead of allocation amount).
So that there is less need to tune RUBY_GC_MALLOC_LIMIT at all, and default
8Mb becomes meaningful.

Before GC relaxation in commit 8c0033a make check ran 13% faster
(292s instead of 338s) and doesn't seems to use more memory. It is now
runs at the same speed, but I propose to revert some part of GC
relaxation.

Tradeoffs for patch simplicity:
- it is not exact: only String, Array, Object, Struct, Bignum and Time are handled
- only one function (xwillfree) introduced. Perhaps, more readable api could be useful.
- xwillfree exposed to the public (ruby.h). Perhaps, it should be in an internal.h,
  but st.c doesn't include internal.h.
  And may be it could be useful for extensions.

https://github.com/ruby/ruby/pull/414
https://github.com/ruby/ruby/pull/414.patch
https://github.com/ruby/ruby/pull/414.diff




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