Import Linux cgroup support

LICENSE-maxprocs.txt

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+MIT License
+
+Copyright (c) 2025 Taiki Kawakami (a.k.a moznion) https://moznion.net
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+--
+
+Copyright (c) 2017 Uber Technologies, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+

ext/etc/lib/etc.rb

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+# frozen_string_literal: true
+
+# MIT License
+#
+# Copyright (c) 2025 Taiki Kawakami (a.k.a moznion) https://moznion.net
+# https://github.com/moznion/maxprocs-ruby/
+
+require "etc.so"
+
+return unless RUBY_PLATFORM.include?("linux")
+
+module Etc
+  # Maxprocs detects CPU quota from Linux cgroups and returns the appropriate
+  # number of processors for container environments.
+  module Maxprocs
+    CGROUP_FILE_PATH = "/proc/self/cgroup"
+    CGROUP_V1_QUOTA_PATH = "/sys/fs/cgroup/cpu/cpu.cfs_quota_us"
+    CGROUP_V1_PERIOD_PATH = "/sys/fs/cgroup/cpu/cpu.cfs_period_us"
+    CGROUP_V2_CONTROLLERS_PATH = "/sys/fs/cgroup/cgroup.controllers"
+    CGROUP_V2_CPU_MAX_PATH = "/sys/fs/cgroup/cpu.max"
+
+    def nprocessors
+      read_quota or super
+    end
+
+    private
+
+    def read_quota
+      return unless File.exist?(CGROUP_FILE_PATH)
+
+      # Check for cgroup v2 first
+      if File.exist?(CGROUP_V2_CONTROLLERS_PATH)
+        read_quota_v2
+      elsif File.exist?(CGROUP_V1_QUOTA_PATH)
+        read_quota_v1
+      end
+    rescue Errno::ENOENT, Errno::EACCES, Errno::EINVAL
+      # File doesn't exist, permission denied, or invalid - fallback to unlimited
+    end
+
+    def read_quota_v1
+      quota = Integer(File.read(CGROUP_V1_QUOTA_PATH))
+      return nil if quota == -1 # -1 means unlimited
+
+      period = Integer(File.read(CGROUP_V1_PERIOD_PATH))
+      return nil if period <= 0
+
+      quota / period
+    end
+
+    def read_quota_v2
+      max_str, period_str = File.read(CGROUP_V2_CPU_MAX_PATH).split(3)
+
+      return nil if max_str == "max" # "max" means unlimited
+      return nil if period_str.nil?
+
+      max = Integer(max_str)
+      period = Integer(period_str)
+      return nil if period <= 0
+
+      max / period
+    end
+  end
+
+  prepend Maxprocs
+  class << self
+    prepend Maxprocs
+  end
+end