get_process_mem

get_mem.rb

require 'ffi'
require 'get_process_mem'
require 'benchmark/ips'

module MemoryInfo
  extend FFI::Library
  ffi_lib 'c'
  attach_function :mach_task_self, [], :__darwin_mach_port_t
  attach_function :task_info, 
                  [
                    :__darwin_mach_port_t,
                    :int,
                    :pointer, #pointer to task info
                    :pointer, #pointer to int
                  ],
                  :int

  class TaskInfo < FFI::Struct
    layout  :suspend_count, :int32,
            :virtual_size, :uint64,
            :resident_size, :uint64,
            :user_time, :uint64,
            :system_time, :uint64,
            :int32, :int32
  end

  MACH_TASK_BASIC_INFO = 20
  MACH_TASK_BASIC_INFO_COUNT = TaskInfo.size / FFI.type_size(:uint)
  

  class << self
    def resident_size
      get_task_info[:resident_size]
    end

    private

    def get_task_info
      data = TaskInfo.new
      out_count = FFI::MemoryPointer.new(:int, 1)
      out_count.write(:uint, MACH_TASK_BASIC_INFO_COUNT)
      result = task_info(mach_task_self, MACH_TASK_BASIC_INFO, data, out_count)
      if result == 0
        data
      else
        raise "task_info returned #{result}"
      end
    end
  end
end

Benchmark.ips do |x|
  x.report(:get_process_mem) { GetProcessMem.new.bytes}
  x.report(:task_info) { MemoryInfo.resident_size}
end

puts GetProcessMem.new.bytes.to_i
puts MemoryInfo.resident_size

output on my machine

Warming up --------------------------------------
     get_process_mem    28.000  i/100ms
           task_info    22.294k i/100ms
Calculating -------------------------------------
     get_process_mem    343.306  (± 3.8%) i/s -      1.736k in   5.064142s
           task_info    252.462k (± 3.2%) i/s -      1.271M in   5.038761s