`class Linux`

Linux implementation of per-process memory metrics using /proc/[pid]/smaps or /proc/[pid]/smaps_rollup, and /proc/[pid]/stat for fault counters. Prefers smaps_rollup when readable (single summary); otherwise falls back to full smaps and counts maps from /proc/[pid]/maps.

Definitions

`def self.capture_faults(pid, usage)`

Extract minor and major page fault counters from /proc/[pid]/stat (proc(5): fields 10=minflt, 12=majflt) and assign to usage.

Signature

parameter　pid　Integer: Process ID.
parameter　usage　Memory: Memory instance to populate with minor_faults and major_faults.

Implementation

def self.capture_faults(pid, usage)
	stat_content = File.read("/proc/#{pid}/stat")
	# The comm field can contain spaces and parentheses; find the closing ')':
	closing_paren_index = stat_content.rindex(")")
	return unless closing_paren_index
	fields = stat_content[(closing_paren_index + 2)..].split(/\s+/)
	# proc(5): field 10=minflt, 12=majflt; our fields array is 0-indexed from field 3.
	usage.minor_faults = fields[10-3].to_i
	usage.major_faults = fields[12-3].to_i
rescue
	# Ignore.
end

`SMAP = {...}`

Mapping from smaps/smaps_rollup line names to Memory struct members (values in kB, converted to bytes when parsing).

Implementation

SMAP = {
	"Rss" => :resident_size,
	"Pss" => :proportional_size,
	"Shared_Clean" => :shared_clean_size,
	"Shared_Dirty" => :shared_dirty_size,
	"Private_Clean" => :private_clean_size,
	"Private_Dirty" => :private_dirty_size,
	"Referenced" => :referenced_size,
	"Anonymous" => :anonymous_size,
	"Swap" => :swap_size,
	"SwapPss" => :proportional_swap_size,
}

`def self.supported?`

Whether the memory usage can be captured on this system.

Implementation

def self.supported?
	true
end

`def self.supported?`

Whether the memory usage can be captured on this system.

Implementation

def self.supported?
	true
end

`def self.capture(pid, faults: true, **options)`

Capture memory usage from /proc/[pid]/smaps_rollup and /proc/[pid]/maps. Optionally fill fault counters from /proc/[pid]/stat.

Signature

parameter　pid　Integer: Process ID.
parameter　faults　Boolean: Whether to capture minor_faults and major_faults (default: true).
returns　Memory | Nil

Implementation

def self.capture(pid, faults: true, **options)
	File.open("/proc/#{pid}/smaps_rollup") do |file|
		usage = Memory.zero
		file.each_line do |line|
			if /(?<name>.*?):\s+(?<value>\d+) kB/ =~ line
				if key = SMAP[name]
					# Convert from kilobytes to bytes:
					usage[key] += value.to_i * 1024
				end
			end
		end
		
		usage.map_count += File.readlines("/proc/#{pid}/maps").size
		
		# Also capture fault counters if requested:
		if faults
			self.capture_faults(pid, usage)
		end
		
		return usage
	end
rescue Errno::ENOENT, Errno::ESRCH, Errno::EACCES
	# Process doesn't exist or we can't access it.
	return nil
end

`def self.capture(pid, faults: true, **options)`

Capture memory usage from /proc/[pid]/smaps (and map count from VmFlags) and /proc/[pid]/maps. Optionally fill fault counters from /proc/[pid]/stat.

Signature

parameter　pid　Integer: Process ID.
parameter　faults　Boolean: Whether to capture minor_faults and major_faults (default: true).
returns　Memory | Nil

Implementation

def self.capture(pid, faults: true, **options)
	File.open("/proc/#{pid}/smaps") do |file|
		usage = Memory.zero
		file.each_line do |line|
			# The format of this is fixed according to:
			# https://github.com/torvalds/linux/blob/351c8a09b00b5c51c8f58b016fffe51f87e2d820/fs/proc/task_mmu.c#L804-L814
			if /(?<name>.*?):\s+(?<value>\d+) kB/ =~ line
				if key = SMAP[name]
					# Convert from kilobytes to bytes:
					usage[key] += value.to_i * 1024
				end
			elsif /VmFlags:\s+(?<flags>.*)/ =~ line
				# It should be possible to extract the number of fibers and each fiber's memory usage.
				# flags = flags.split(/\s+/)
				usage.map_count += 1
			end
		end
		
		# Also capture fault counters if requested:
		if faults
			self.capture_faults(pid, usage)
		end
		
		return usage
	end
rescue Errno::ENOENT, Errno::ESRCH, Errno::EACCES
	# Process doesn't exist or we can't access it.
	return nil
end