November 19

Python: Script to break down what is using memory / RAM

#!/usr/bin/env python

# Try to determine how much RAM is currently being used per program.
# Note per _program_, not per process. So for example this script
# will report RAM used by all httpd process together. In detail it reports:
# sum(private RAM for program processes) + sum(Shared RAM for program processes)
# The shared RAM is problematic to calculate, and this script automatically
# selects the most accurate method available for your kernel.

# Licence: LGPLv2
# Author:  [email protected]
# Source:

# V1.0      06 Jul 2005     Initial release
# V1.1      11 Aug 2006     root permission required for accuracy
# V1.2      08 Nov 2006     Add total to output
#                           Use KiB,MiB,... for units rather than K,M,...
# V1.3      22 Nov 2006     Ignore shared col from /proc/$pid/statm for
#                           2.6 kernels up to and including 2.6.9.
#                           There it represented the total file backed extent
# V1.4      23 Nov 2006     Remove total from output as it's meaningless
#                           (the shared values overlap with other programs).
#                           Display the shared column. This extra info is
#                           useful, especially as it overlaps between programs.
# V1.5      26 Mar 2007     Remove redundant recursion from human()
# V1.6      05 Jun 2007     Also report number of processes with a given name.
#                           Patch from [email protected]
# V1.7      20 Sep 2007     Use PSS from /proc/$pid/smaps if available, which
#                           fixes some over-estimation and allows totalling.
#                           Enumerate the PIDs directly rather than using ps,
#                           which fixes the possible race between reading
#                           RSS with ps, and shared memory with this program.
#                           Also we can show non truncated command names.
# V1.8      28 Sep 2007     More accurate matching for stats in /proc/$pid/smaps
#                           as otherwise could match libraries causing a crash.
#                           Patch from [email protected]
# V1.9      20 Feb 2008     Fix invalid values reported when PSS is available.
#                           Reported by Andrey Borzenkov <[email protected]>
# V3.3      24 Jun 2014

# Notes:
# All interpreted programs where the interpreter is started
# by the shell or with env, will be merged to the interpreter
# (as that's what's given to exec). For e.g. all python programs
# starting with "#!/usr/bin/env python" will be grouped under python.
# You can change this by using the full command line but that will
# have the undesirable affect of splitting up programs started with
# differing parameters (for e.g. mingetty tty[1-6]).
# For 2.6 kernels up to and including 2.6.13 and later 2.4 redhat kernels
# (rmap vm without smaps) it can not be accurately determined how many pages
# are shared between processes in general or within a program in our case:
# A warning is printed if overestimation is possible.
# In addition for 2.6 kernels up to 2.6.9 inclusive, the shared
# value in /proc/$pid/statm is the total file-backed extent of a process.
# We ignore that, introducing more overestimation, again printing a warning.
# Since kernel 2.6.23-rc8-mm1 PSS is available in smaps, which allows
# us to calculate a more accurate value for the total RAM used by programs.
# Programs that use CLONE_VM without CLONE_THREAD are discounted by assuming
# they're the only programs that have the same /proc/$PID/smaps file for
# each instance.  This will fail if there are multiple real instances of a
# program that then use CLONE_VM without CLONE_THREAD, or if a clone changes
# its memory map while we're checksumming each /proc/$PID/smaps.
# I don't take account of memory allocated for a program
# by other programs. For e.g. memory used in the X server for
# a program could be determined, but is not.
# FreeBSD is supported if linprocfs is mounted at /compat/linux/proc/
# FreeBSD 8.0 supports up to a level of Linux 2.6.16

import getopt
import time
import errno
import os
import sys

    # md5 module is deprecated on python 2.6
    # so try the newer hashlib first
    import hashlib
    md5_new = hashlib.md5
except ImportError:
    import md5
    md5_new =

# The following exits cleanly on Ctrl-C or EPIPE
# while treating other exceptions as before.
def std_exceptions(etype, value, tb):
    sys.excepthook = sys.__excepthook__
    if issubclass(etype, KeyboardInterrupt):
    elif issubclass(etype, IOError) and value.errno == errno.EPIPE:
        sys.__excepthook__(etype, value, tb)
sys.excepthook = std_exceptions

#   Define some global variables

PAGESIZE = os.sysconf("SC_PAGE_SIZE") / 1024 #KiB
our_pid = os.getpid()

have_pss = 0

class Proc:
    def __init__(self):
        uname = os.uname()
        if uname[0] == "FreeBSD":
            self.proc = '/compat/linux/proc'
            self.proc = '/proc'

    def path(self, *args):
        return os.path.join(self.proc, *(str(a) for a in args))

    def open(self, *args):
            return open(self.path(*args))
        except (IOError, OSError):
            val = sys.exc_info()[1]
            if (val.errno == errno.ENOENT or # kernel thread or process gone
                val.errno == errno.EPERM):
                raise LookupError

proc = Proc()

#   Functions

def parse_options():
        long_options = ['split-args', 'help', 'total']
        opts, args = getopt.getopt(sys.argv[1:], "shtp:w:", long_options)
    except getopt.GetoptError:

    if len(args):
        sys.stderr.write("Extraneous arguments: %s\n" % args)

    # options
    split_args = False
    pids_to_show = None
    watch = None
    only_total = False

    for o, a in opts:
        if o in ('-s', '--split-args'):
            split_args = True
        if o in ('-t', '--total'):
            only_total = True
        if o in ('-h', '--help'):
        if o in ('-p',):
                pids_to_show = [int(x) for x in a.split(',')]
        if o in ('-w',):
                watch = int(a)

    return (split_args, pids_to_show, watch, only_total)

def help():
    help_msg = 'Usage: ps_mem [OPTION]...\n' \
    'Show program core memory usage\n' \
    '\n' \
    '  -h, -help                   Show this help\n' \
    '  -p <pid>[,pid2,...pidN]     Only show memory usage PIDs in the specified list\n' \
    '  -s, --split-args            Show and separate by, all command line arguments\n' \
    '  -t, --total                 Show only the total value\n' \
    '  -w <N>                      Measure and show process memory every N seconds\n'

    return help_msg

def kernel_ver():
    kv ='sys/kernel/osrelease').readline().split(".")[:3]
    last = len(kv)
    if last == 2:
    last -= 1
    while last > 0:
        for char in "-_":
            kv[last] = kv[last].split(char)[0]
            kv[last] = 0
        last -= 1
    return (int(kv[0]), int(kv[1]), int(kv[2]))

#return Private,Shared
#Note shared is always a subset of rss (trs is not always)
def getMemStats(pid):
    global have_pss
    mem_id = pid #unique
    Private_lines = []
    Shared_lines = []
    Pss_lines = []
    Rss = (int(, 'statm').readline().split()[1])
           * PAGESIZE)
    if os.path.exists(proc.path(pid, 'smaps')): #stat
        digester = md5_new()
        for line in, 'smaps').readlines(): #open
            # Note we checksum smaps as maps is usually but
            # not always different for separate processes.
            if line.startswith("Shared"):
            elif line.startswith("Private"):
            elif line.startswith("Pss"):
                have_pss = 1
        mem_id = digester.hexdigest()
        Shared = sum([int(line.split()[1]) for line in Shared_lines])
        Private = sum([int(line.split()[1]) for line in Private_lines])
        #Note Shared + Private = Rss above
        #The Rss in smaps includes video card mem etc.
        if have_pss:
            pss_adjust = 0.5 # add 0.5KiB as this avg error due to trunctation
            Pss = sum([float(line.split()[1])+pss_adjust for line in Pss_lines])
            Shared = Pss - Private
    elif (2,6,1) <= kernel_ver() <= (2,6,9):
        Shared = 0 #lots of overestimation, but what can we do?
        Private = Rss
        Shared = int(, 'statm').readline().split()[2])
        Shared *= PAGESIZE
        Private = Rss - Shared
    return (Private, Shared, mem_id)

def getCmdName(pid, split_args):
    cmdline =, 'cmdline').read().split("\0")
    if cmdline[-1] == '' and len(cmdline) > 1:
        cmdline = cmdline[:-1]

    path = proc.path(pid, 'exe')
        path = os.readlink(path)
        # Some symlink targets were seen to contain NULs on RHEL 5 at least
        #, so take string up to NUL
        path = path.split('\0')[0]
    except OSError:
        val = sys.exc_info()[1]
        if (val.errno == errno.ENOENT or # either kernel thread or process gone
            val.errno == errno.EPERM):
            raise LookupError

    if split_args:
        return " ".join(cmdline)
    if path.endswith(" (deleted)"):
        path = path[:-10]
        if os.path.exists(path):
            path += " [updated]"
            #The path could be have prelink stuff so try cmdline
            #which might have the full path present. This helped for:
            #/usr/libexec/notification-area-applet.#prelink#.fX7LCT (deleted)
            if os.path.exists(cmdline[0]):
                path = cmdline[0] + " [updated]"
                path += " [deleted]"
    exe = os.path.basename(path)
    cmd =, 'status').readline()[6:-1]
    if exe.startswith(cmd):
        cmd = exe #show non truncated version
        #Note because we show the non truncated name
        #one can have separated programs as follows:
        #584.0 KiB +   1.0 MiB =   1.6 MiB    mozilla-thunder (exe -> bash)
        # 56.0 MiB +  22.2 MiB =  78.2 MiB    mozilla-thunderbird-bin
    return cmd

#The following matches "du -h" output
#see also
def human(num, power="Ki", units=None):
    if units is None:
        powers = ["Ki", "Mi", "Gi", "Ti"]
        while num >= 1000: #4 digits
            num /= 1024.0
            power = powers[powers.index(power)+1]
        return "%.1f %sB" % (num, power)
        return "%.f" % ((num * 1024) / units)

def cmd_with_count(cmd, count):
    if count > 1:
        return "%s (%u)" % (cmd, count)
        return cmd

#Warn of possible inaccuracies
#2 = accurate & can total
#1 = accurate only considering each process in isolation
#0 = some shared mem not reported
#-1= all shared mem not reported
def shared_val_accuracy():
    kv = kernel_ver()
    pid = os.getpid()
    if kv[:2] == (2,4):
        if'meminfo').read().find("Inact_") == -1:
            return 1
        return 0
    elif kv[:2] == (2,6):
        if os.path.exists(proc.path(pid, 'smaps')):
            if, 'smaps').read().find("Pss:")!=-1:
                return 2
                return 1
        if (2,6,1) <= kv <= (2,6,9):
            return -1
        return 0
    elif kv[0] > 2 and os.path.exists(proc.path(pid, 'smaps')):
        return 2
        return 1

def show_shared_val_accuracy( possible_inacc, only_total=False ):
    level = ("Warning","Error")[only_total]
    if possible_inacc == -1:
         "%s: Shared memory is not reported by this system.\n" % level
         "Values reported will be too large, and totals are not reported\n"
    elif possible_inacc == 0:
         "%s: Shared memory is not reported accurately by this system.\n" % level
         "Values reported could be too large, and totals are not reported\n"
    elif possible_inacc == 1:
         "%s: Shared memory is slightly over-estimated by this system\n"
         "for each program, so totals are not reported.\n" % level
    if only_total and possible_inacc != 2:

def get_memory_usage( pids_to_show, split_args, include_self=False, only_self=False ):
    cmds = {}
    shareds = {}
    mem_ids = {}
    count = {}
    for pid in os.listdir(proc.path('')):
        if not pid.isdigit():
        pid = int(pid)

        # Some filters
        if only_self and pid != our_pid:
        if pid == our_pid and not include_self:
        if pids_to_show is not None and pid not in pids_to_show:

            cmd = getCmdName(pid, split_args)
        except LookupError:
            #operation not permitted
            #kernel threads don't have exe links or
            #process gone

            private, shared, mem_id = getMemStats(pid)
        except RuntimeError:
            continue #process gone
        if shareds.get(cmd):
            if have_pss: #add shared portion of PSS together
                shareds[cmd] += shared
            elif shareds[cmd] < shared: #just take largest shared val
                shareds[cmd] = shared
            shareds[cmd] = shared
        cmds[cmd] = cmds.setdefault(cmd, 0) + private
        if cmd in count:
            count[cmd] += 1
            count[cmd] = 1
        mem_ids.setdefault(cmd, {}).update({mem_id:None})

    #Add shared mem for each program
    total = 0
    for cmd in cmds:
        cmd_count = count[cmd]
        if len(mem_ids[cmd]) == 1 and cmd_count > 1:
            # Assume this program is using CLONE_VM without CLONE_THREAD
            # so only account for one of the processes
            cmds[cmd] /= cmd_count
            if have_pss:
                shareds[cmd] /= cmd_count
        cmds[cmd] = cmds[cmd] + shareds[cmd]
        total += cmds[cmd] #valid if PSS available

    sorted_cmds = sorted(cmds.items(), key=lambda x:x[1])
    sorted_cmds = [x for x in sorted_cmds if x[1]]

    return sorted_cmds, shareds, count, total

def print_header():
    sys.stdout.write(" Private  +   Shared  =  RAM used\tProgram\n\n")

def print_memory_usage(sorted_cmds, shareds, count, total):
    for cmd in sorted_cmds:
        sys.stdout.write("%9s + %9s = %9s\t%s\n" %
                          human(shareds[cmd[0]]), human(cmd[1]),
                          cmd_with_count(cmd[0], count[cmd[0]])))
    if have_pss:
        sys.stdout.write("%s\n%s%9s\n%s\n" %
                         ("-" * 33, " " * 24, human(total), "=" * 33))

def verify_environment():
    if os.geteuid() != 0:
        sys.stderr.write("Sorry, root permission required.\n")
        if __name__ == '__main__':

        kv = kernel_ver()
    except (IOError, OSError):
        val = sys.exc_info()[1]
        if val.errno == errno.ENOENT:
              "Couldn't access " + proc.path('') + "\n"
              "Only GNU/Linux and FreeBSD (with linprocfs) are supported\n")

if __name__ == '__main__':
    split_args, pids_to_show, watch, only_total = parse_options()

    if not only_total:

    if watch is not None:
            sorted_cmds = True
            while sorted_cmds:
                sorted_cmds, shareds, count, total = get_memory_usage( pids_to_show, split_args )
                if only_total and have_pss:
                    sys.stdout.write(human(total, units=1)+'\n')
                elif not only_total:
                    print_memory_usage(sorted_cmds, shareds, count, total)
                sys.stdout.write('Process does not exist anymore.\n')
        except KeyboardInterrupt:
        # This is the default behavior
        sorted_cmds, shareds, count, total = get_memory_usage( pids_to_show, split_args )
        if only_total and have_pss:
            sys.stdout.write(human(total, units=1)+'\n')
        elif not only_total:
            print_memory_usage(sorted_cmds, shareds, count, total)

    # We must close explicitly, so that any EPIPE exception
    # is handled by our excepthook, rather than the default
    # one which is reenabled after this script finishes.

    vm_accuracy = shared_val_accuracy()
    show_shared_val_accuracy( vm_accuracy, only_total )

Copyright 2021. All rights reserved.

Posted November 19, 2021 by Timothy Conrad in category "Programming

About the Author

If I were to describe myself with one word it would be, creative. I am interested in almost everything which keeps me rather busy. Here you will find some of my technical musings. PGP: 4CB8 91EB 0C0A A530 3BE9 6D76 B076 96F1 6135 0A1B