树莓派OLED监控脚本CPU占用过高问题排查与优化咨询

问题背景 #

我从diy-life找到树莓派OLED状态显示项目，优化其Python代码添加图标并提升监控信息准确性后，发现脚本CPU占用远高于其他空闲服务，通过Grafana的cAdvisor数据显示其占用10%CPU。猜测是每秒更新导致，但不确定这是否是唯一原因。相关优化PR已提交。

高CPU占用的核心原因 #

并非只有"每秒更新"这一个因素，以下是主要诱因：

• 无间隔循环执行：脚本中sleep变量设为0，外层while True循环几乎不间断运行，CPU始终处于被调用状态，没有休息时间。
• 频繁创建子进程开销大：每次循环通过subprocess.check_output执行8个独立shell命令（如ip addr、vmstat、free等），每个命令都需要创建新的子进程。树莓派的ARM架构CPU处理子进程创建和销毁的开销远高于x86平台，这是CPU占用高的关键原因之一。
• vmstat命令的等待逻辑：获取CPU使用率的vmstat 1 2命令会主动等待1秒采样数据，虽然这段时间脚本处于阻塞状态，但结合无间隔循环，整体会让CPU始终处于忙碌状态，叠加其他命令的执行开销，进一步拉高占用率。
• 冗余嵌套循环：内层while (time_in_range(...))循环在时间范围内持续执行，没有额外休眠，加剧了CPU消耗。

优化方案 #

1. 添加合理休眠时间 #

将sleep变量调整为2-5秒（比如sleep = 3），减少循环执行频率。OLED屏幕无需每秒刷新，既降低CPU占用，也能延长屏幕寿命。

2. 用Python模块替代shell命令 #

使用psutil模块直接获取系统信息，避免创建子进程。安装命令：

pip install psutil

替换后的核心逻辑示例：

import psutil

# 获取CPU使用率（直接采样，无需等待）
cpu_usage = psutil.cpu_percent(interval=0.1)
# 获取内存信息
mem = psutil.virtual_memory()
mem_used = round(mem.used / 1024**3, 1)
mem_total = round(mem.total / 1024**3, 0)
mem_percent = mem.percent
# 获取磁盘使用情况
disk = psutil.disk_usage('/')
disk_percent = f"{disk.percent}%"
# 获取CPU温度（树莓派专属）
def get_cpu_temp():
    with open('/sys/class/thermal/thermal_zone0/temp', 'r') as f:
        return round(int(f.read())/1000, 1)
temp = get_cpu_temp()
# 获取IP地址
def get_ip():
    for iface in psutil.net_if_addrs().values():
        for addr in iface:
            if addr.family == 2 and not addr.address.startswith('127.'):
                return addr.address
ip = get_ip()
# 获取运行时间
uptime = psutil.boot_time()
uptime_days = round((time.time() - uptime)/86400, 1)
uptime_str = f"{uptime_days} days"

3. 优化循环结构 #

简化嵌套循环，将时间判断和休眠逻辑整合，避免不必要的循环迭代：

while True:
    current = datetime.datetime.now().time()
    if time_in_range(start, end, current):
        # 执行数据采集和屏幕绘制逻辑
        oled.image(image)
        oled.show()
        time.sleep(sleep)
    else:
        oled.fill(0)
        oled.show()
        time.sleep(60)

4. 复用静态元素绘制 #

图标属于静态元素，可在循环外提前绘制到基础图像中，循环内仅更新动态数据部分，减少PIL的绘制操作开销。

原脚本代码 #

#!/usr/bin/env python3
# For Raspberry Pi Desktop Case with OLED Stats Display
# Base on Adafruit CircuitPython & SSD1306 Libraries
# Installation & Setup Instructions - https://www.the-diy-life.com/add-an-oled-stats-display-to-raspberry-pi-os-bullseye/
import time
import board
import busio
import digitalio
import adafruit_ssd1306
import subprocess
import datetime
from PIL import Image, ImageDraw, ImageFont

def time_in_range(start, end, current):
    # Returns whether current is in the range [start, end]
    return start <= current <= end

# Display Parameters
width = 128
height = 64

# Font size
font_sz = 16

# Wait with refresh after showing all stats (takes a second)
sleep = 0

# When the display should be on e.g. 8:30 (8, 30, 0) up to 23:00
start = datetime.time(0, 0, 0)
end = datetime.time(0, 0, 0)
current = datetime.datetime.now().time()

# Methode to control the display with oled func
oled = adafruit_ssd1306.SSD1306_I2C(width, height, board.I2C(), addr=0x3C, reset=digitalio.DigitalInOut(board.D4))

# Clear display.
oled.fill(0)
oled.show()

# Create a blank image for drawing in 1-bit color
image = Image.new('1', (oled.width, oled.height))

# Get drawing object to draw on image
draw = ImageDraw.Draw(image)

# Import custom fonts
font = ImageFont.truetype('PixelOperator.ttf', font_sz)
icon_font= ImageFont.truetype('lineawesome-webfont.ttf', font_sz)
while True:
    while (time_in_range(start, end, current)):
        current = datetime.datetime.now().time()
        draw.rectangle((0, 0, oled.width, oled.height), fill=0) # Draw a black filled box to clear the image.
        cmd = "ip addr | awk '/inet / { print $2 }' | sed -n '2{p;q}' | cut -d '/' -f1" # Command that's executed in bash
        IP = subprocess.check_output(cmd, shell = True ) # Register ouput from cmd in var
        cmd = "vmstat 1 2|tail -1|awk '{print 100-$15}' | tr -d '\n'" # Takes a second to fetch for accurate cpu usage in %
        CPU = subprocess.check_output(cmd, shell = True )
        cmd = "free -m | awk 'NR==2{printf $3}'| awk '{printf $1/1000}'"
        Memuse = subprocess.check_output(cmd, shell = True )
        cmd = "cat /proc/meminfo | head -n 1 | awk -v CONVFMT='%.0f' '{printf $2/1000000}'"
        MemTotal = subprocess.check_output(cmd, shell = True )
        cmd = "free -m | awk -v CONVFMT='%.1f' 'NR==2{printf $3*100/$2}'"
        Memuseper = subprocess.check_output(cmd, shell = True )
        cmd = "df -h | awk '$NF==\"/\"{printf \"%s\", $5}'"
        Disk = subprocess.check_output(cmd, shell = True )
        #cmd = "uptime=$(</proc/uptime) ;  uptime=${uptime%%.*} ; days=$(( uptime/60/60/24 )); echo $days days"
        cmd = "uptime | awk '{print $3,$4}' | cut -f1 -d','"
        uptime = subprocess.check_output(cmd, shell = True )
        cmd = "cat /sys/class/thermal/thermal_zone*/temp | awk -v CONVFMT='%.1f' '{printf $1/1000}'"   
        temp = subprocess.check_output(cmd, shell = True )

        # We draw the icons seprately and offset by a fixed amount later
        # Icon wifi, chr num comes from unicode &#xf1eb; to decimal 61931 (Use: https://www.binaryhexconverter.com/hex-to-decimal-converter)
        draw.text((1, 0), chr(61931), font=icon_font, fill=255) # Offset the icon on the x-as a little and devide the y-as in steps of 16
        # Icon cpu
        draw.text((1, 16), chr(62171), font=icon_font, fill=255)
        # Icon temp right
        draw.text((111, 16), chr(62153), font=icon_font, fill=255) # Offset the icon from the left to the farthest right
        # Icon memory
        draw.text((1, 32), chr(62776), font=icon_font, fill=255)
        # Icon disk
        draw.text((1, 48), chr(63426), font=icon_font, fill=255)
        # Icon temp right
        draw.text((111, 48), chr(62034), font=icon_font, fill=255)

        # Pi Stats Display, printed from left to right each line
        draw.text((22, 0), str(IP,'utf-8'), font=font, fill=255) # x y followed by the content to be printed on the display followed by how it should be printed
        draw.text((22, 16), str(CPU,'utf-8') + "%", font=font, fill=255)
        draw.text((107, 16), str(temp,'utf-8') + "°C", font=font, fill=255, anchor="ra") # anchor basically refers to printing right to left: https://pillow.readthedocs.io/en/stable/handbook/text-anchors.html#specifying-an-anchor
        draw.text((22, 32), str(Memuseper,'utf-8') + "%", font=font, fill=255)
        draw.text((125, 32), str(Memuse,'utf-8') + "/" + str(MemTotal,'utf-8') + "G", font=font, fill=255, anchor="ra")
        draw.text((22, 48), str(Disk,'utf-8'), font=font, fill=255)
        draw.text((107, 48), str(uptime,'utf-8'), font=font, fill=255, anchor="ra")

        # Display image
        oled.image(image)
        oled.show()
    else:
        oled.fill(0)
        oled.show()
        sleep(60)
        current = datetime.datetime.now().time()
    time.sleep(sleep)

内容的提问来源于stack exchange，提问作者Macley