Issue #22466 has been reported by jeremyevans0 (Jeremy Evans). ---------------------------------------- Feature #22466: Allow disabling the shape redblack cache via RUBY_SHAPE_REDBLACK_CACHE=disable https://bugs.ruby-lang.org/issues/22466 * Author: jeremyevans0 (Jeremy Evans) * Status: Open ---------------------------------------- The shape redblack cache mmaps 384MB of memory at startup. There is currently no way to configure the amount of memory used. The code already handles an mmap failure cleanly. I would like a way to skip the mmap attempt, and the simplest way I can think of is an environment variable. The reason behind the current behavior (I think) is that ruby currently assumes that the mmap is basically free, since the memory is not actually allocated in most cases. However, when operating system strict memory overcommit is used, this 384MB mmap allocation can result in the serious problems later with the operating system killing the process if it is low on memory. This provides a way to accept a performance hit and avoid the memory allocation. We are currently working around this issue in production by decreasing the amount of memory available to the process at startup to 256MB (causing the mmap allocation to fail), and then increasing it after startup using `Process.setrlimit`. However, that results in a lot of additional complexity that I would prefer to avoid. If it is preferable to specify the cache size via an environment variable, instead of just the ability to disable the cache, I can work on that approach instead. I submitted a pull request to implement this: https://github.com/ruby/ruby/pull/19499 -- https://bugs.ruby-lang.org/