Getting memory usage by python

Question

I am having trouble retrieving memory usage of my system using psutil.

When I run my code it retrieves the cpu usage correctly, but when it tries to get the memory it throws an AccessDenied error.

code:

if(pi['name']=='java.exe'):
    pro=psutil.Process(0)
    cpu=pro.cpu_percent(1)
    memory=pro.memory_full_info().uss/(1024*1024)
    return memory,cpu

Error message:

psutil.AccessDenied (pid=0)

How can i get memory usage?

This suggests that your script doesn't have access to get that processes information. Have you tried running your script as an admin / root? — Oliver.R, Mar 19 '20 at 04:37
For Windows, [this SO thread](https://stackoverflow.com/a/39948482/10993299) provides information on running a VSCode instance as admin every time it launches. For a one-time admin run of VSCode, shift+right-click VSCode, and "Run as Administrator". — Oliver.R, Mar 19 '20 at 04:50
I'm also assuming that none of the basic [`memory_info()`](https://psutil.readthedocs.io/en/latest/#psutil.Process.memory_info) details will provide sufficient information for you (they don't require elevated priveleges). — Oliver.R, Mar 19 '20 at 04:55
pid 0 aka *System Idle Process* requires `SYSTEM` privileges -- higher than admin. Do you really want to know its memory usage, or do you actually want to know `java.exe`'s memory usage? See my answer. — GordonAitchJay, Mar 19 '20 at 06:43

score 0 · Accepted Answer · answered Mar 19 '20 at 06:33

psutil.Process() takes one argument - a process identifier (PID). If it is called without an argument or with None, then the pid of the current process is used.

On Window, pid 0 is the The System Idle Process, which requires SYSTEM privileges.

pro=psutil.Process(0) # here's your problem

If you want to get the memory/cpu usage of java.exe, you'll have to get the pid, then use psutil. In the example below, I have used firefox.exe:

import psutil
from ctypes import *
from ctypes.wintypes import *

class PROCESSENTRY32W(Structure):
    _fields_ = [("dwSize", DWORD),
                ("cntUsage", DWORD),
                ("th32ProcessID", DWORD),
                ("th32DefaultHeapID", POINTER(ULONG)),
                ("th32ModuleID", DWORD),
                ("cntThreads", DWORD),
                ("th32ParentProcessID", DWORD),
                ("pcPriClassBase", LONG),
                ("dwFlags", DWORD),
                ("szExeFile", c_wchar * MAX_PATH)]

def get_processes():
    TH32CS_SNAPPROCESS = 0x00000002
    INVALID_HANDLE_VALUE = -1

    CreateToolhelp32Snapshot = windll.kernel32.CreateToolhelp32Snapshot
    CreateToolhelp32Snapshot.argtypes = [DWORD, DWORD]
    CreateToolhelp32Snapshot.restype = HANDLE

    Process32FirstW = windll.kernel32.Process32FirstW
    Process32FirstW.argtypes = [HANDLE, POINTER(PROCESSENTRY32W)]
    Process32FirstW.restype = BOOL

    Process32NextW = windll.kernel32.Process32NextW
    Process32NextW.argtypes = [HANDLE, POINTER(PROCESSENTRY32W)]
    Process32NextW.restype = BOOL

    CloseHandle = windll.kernel32.CloseHandle
    CloseHandle.argtypes = [HANDLE]
    CloseHandle.restype = BOOL

    snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)
    if snapshot == INVALID_HANDLE_VALUE:
        return []

    try:
        process_entry = PROCESSENTRY32W()
        process_entry.dwSize = sizeof(PROCESSENTRY32W)
        if not Process32FirstW(snapshot, byref(process_entry)):
            return []

        processes = []
        while Process32NextW(snapshot, byref(process_entry)):
            processes.append((process_entry.th32ProcessID, process_entry.szExeFile))
    finally:
        CloseHandle(snapshot)
        #print("Closed handle")

    return processes

for pid, name in get_processes():
    if name == "firefox.exe":
        pro = psutil.Process(pid)
        cpu = pro.cpu_percent(1.0)
        memory = pro.memory_full_info().uss/(1024*1024)
        print(memory, cpu)

Output:

471.2890625 1.6
127.15234375 25.0
18.50390625 0.0
668.09375 0.0
706.6875 0.0
512.671875 0.0
648.953125 4.7
1037.0859375 4.7
1160.1015625 98.4
337.46484375 0.0
1418.72265625 1.6
0.90625 0.0
0.90625 0.0

Getting memory usage by python

1 Answers1