[ruby-core:28491] [Feature #905] Add String.new(fixnum) to preallocate large buffer

Issue #905 has been updated by Kurt  Stephens.


+1

Preallocation of String would be immensely useful in large ERB templates.

So much so, I was looking to patching into rb_str_resize(str, len) with a method, to get around related performance issues.  Ruby Strings already support the difference between the string length and the allocated buffer size -- we need to expose it and ensure that Strings do not automatically "shrink" the internal String buffers.  There should probably be a method to explicitly shrink the internal buffer, if needed.

From what I can tell string growth is roughly O(log2 N) because of the power-of-2 buffer resizing.   For large buffers making this O(1) for large strings helps performance and reduces malloc() memory fragmentation.



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