win/linux 下使用 psutil 獲取進程 CPU / memory / IO 占用信息

psutil - A cross-platform process and system utilities module for Python

1. 安裝

pip 安裝即可。

windows 下需要安裝 vs2008，否則報錯： Unable to find vcvarsall.bat 

如果已經安裝 vs2010 / vs2012 則需要設置環境變量，VS90COMNTOOLS 指向已有的 vs 變量。

vs2010 設置如下：

VS90COMNTOOLS = %VS100COMNTOOLS%

2. 獲取特定進程對象

• 根據進程 ID 創建進程對象
• 獲取所有進程對象，過濾出目標進程

# -*- coding: utf-8-*-
import psutil

def get_proc_by_id(pid):
    return psutil.Process(pid)

def get_proc_by_name(pname):
    """ get process by name
    
    return the first process if there are more than one
    """
    for proc in psutil.process_iter():
        try:
            if proc.name().lower() == pname.lower():
                return proc  # return if found one
        except psutil.AccessDenied:
            pass
        except psutil.NoSuchProcess:
            pass
    return None


if '__main__' == __name__:
    print get_proc_by_name("chrome.exe")
    print get_proc_by_id(4364)

3. 獲取進程信息

3.1 需要特別注意異常保護，尤其是  psutil.AccessDenied

不同的進程，權限等信息可能不同，遍歷所有進程取信息時，需要對每一個進程單獨進程異常保護。

3.2 獲取所有進程

大多數 demo 代碼中，都是使用  psutil.get_process_list ，但該方法在源碼中已經標記為廢棄。

新推薦的是  psutil.process_iter 迭代器。

根據下面的源碼可知實現原理：獲取所有進程 ID，然后根據 ID 創建進程對象。

_pmap = {}

def process_iter():
    """Return a generator yielding a Process class instance for all
    running processes on the local machine.

    Every new Process instance is only created once and then cached
    into an internal table which is updated every time this is used.

    Cached Process instances are checked for identity so that you're
    safe in case a PID has been reused by another process, in which
    case the cached instance is updated.

    The sorting order in which processes are yielded is based on
    their PIDs.
    """
    def add(pid):
        proc = Process(pid)
        _pmap[proc.pid] = proc
        return proc

    def remove(pid):
        _pmap.pop(pid, None)

    a = set(get_pid_list())
    b = set(_pmap.keys())
    new_pids = a - b
    gone_pids = b - a

    for pid in gone_pids:
        remove(pid)
    for pid, proc in sorted(list(_pmap.items()) + \
                            list(dict.fromkeys(new_pids).items())):
        try:
            if proc is None:  # new process
                yield add(pid)
            else:
                # use is_running() to check whether PID has been reused by
                # another process in which case yield a new Process instance
                if proc.is_running():
                    yield proc
                else:
                    yield add(pid)
        except NoSuchProcess:
            remove(pid)
        except AccessDenied:
            # Process creation time can't be determined hence there's
            # no way to tell whether the pid of the cached process
            # has been reused. Just return the cached version.
            yield proc
@_deprecated()
def get_process_list():
    """Return a list of Process class instances for all running
    processes on the local machine (deprecated).
    """
    return list(process_iter())

3.3 進程的內存信息 -- VSS/RSS/PSS/USS

VSS 是剩余的可訪問內存。

進程占用內存包括 2 部分，自身 + 共享庫。不同的算法產生了 3 個不同的內存指標，分別是：RSS / PSS / USS。

一般來說內存占用大小有如下規律：VSS >= RSS >= PSS >= USS

 

Demo 代碼如下

proc = psutil.Process(4364)

total = psutil.virtual_memory().total
rss, vss = proc.memory_info()
percent = proc.memory_percent()

print "rss: %s Byte, vss: %s Byte" % (rss, vss)
print "total: %.2f(M)" % (float(total)/1024/1024/1024)
print "percent: %.2f%%, calc: %.2f%%" % (percent, 100*float(rss)/total)

輸出

本機內存信息截圖

詳細說明：

• VSS(reported as VSZ from ps) is the total accessible address space of a process. 
  This size also includes memory that may not be resident in RAM like mallocs that have been allocated but not written to.
  VSS is of very little use for determing real memory usage of a process.
• RSS is the total memory actually held in RAM for a process.
  RSS can be misleading, because it reports the total all of the shared libraries that the process uses,
  even though a shared library is only loaded into memory once regardless of how many processes use it.
  RSS is not an accurate representation of the memory usage for a single process.
• PSS differs from RSS in that it reports the proportional size of its shared libraries,
  i.e. if three processes all use a shared library that has 30 pages,
  that library will only contribute 10 pages to the PSS that is reported for each of the three processes.
  PSS is a very useful number because when the PSS for all processes in the system are summed together,
  that is a good representation for the total memory usage in the system.
  When a process is killed, the shared libraries that contributed to its PSS
  will be proportionally distributed to the PSS totals for the remaining processes still using that library.
  In this way PSS can be slightly misleading, because
  when a process is killed, PSS does not accurately represent the memory returned to the overall system.
• USS is the total private memory for a process,
  i.e. that memory that is completely unique to that process.
  USS is an extremely useful number because it indicates the true incremental cost of running a particular process.
  When a process is killed, the USS is the total memory that is actually returned to the system.
  USS is the best number to watch when initially suspicious ofmemory leaksin a process.