Get real memory (resident set) used by current Ruby process

process_rss.rb

#
# This first version should work on Mac OS X and Linux, but it spawns a process
#
#     http://stackoverflow.com/questions/7220896/
#     https://github.com/rdp/os/blob/master/lib/os.rb#L127
#     http://www.ruby-doc.org/core-2.0/Process.html
#

# the real memory (resident set) size of the process (in 1_024 byte units).
def Process.rss() `ps -o rss= -p #{Process.pid}`.chomp.to_i ; end

#
# This second version depends on the /proc filesystem, so won't work on Mac OS X
#
#     https://www.kernel.org/doc/Documentation/filesystems/proc.txt
#     >> Table 1-3 << Contents of the statm files (as of 2.6.8-rc3)
#
#     Note that this implementation assumes that the size of memory
#     pages is 4_096 bytes, ie. 4kB, which is a widespread default!
#
#     However, it is probably best to check this assumption on your
#     architecture, using `getconf PAGESIZE` or `getconf PAGE_SIZE`
#

# returns detailed information about the process memory usage (as recorded in the "/proc/$$/statm" proc fs file)
def Process.statm() Hash[%i{size resident shared trs lrs drs dt}.zip(open("/proc/#{Process.pid}/statm").read.split)] ; end

# the real memory (resident set) size of the process (in 1_024 byte units, assuming a 4kB memory page size)
def Process.rss() Process.statm[:resident].to_i * 4 ; end

#
# Some pretty formatting, on top of either of the above implementations
#

def Process.pretty_rss(rss = Process.rss) rss.to_s.gsub(/(\d)(?=(\d{3})+(\..*)?$)/,'\1,') + " kilobytes" ; end