[C#]透過PerformanceCounter取得特定Process的CPU使用率

2013-03-18

28243
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C#

想要透過PerformanceCounter取得特定Process的CPU使用率，首先我們要理解這部分的資料在PerformanceCounter是怎樣分布的。這邊我們可以叫出效能監視器後，找到Process分類，可以看到如下畫面，所有的Process都有對應的Instance，像是chrome、chrome#1、chrome#11...。

所以我們的第一步就是要從Process找到對應的Process Instance Name。但是BCL內建的Process類別中並未有這樣的資訊，要怎樣找到呢？這邊可透過另一個名叫ID Process的PerformanceCounter輔助，對照筆者準備的兩張圖，不難發現該PerformanceCounter的值對應的就是Process的PID。

這給我們了一個提示，我們可透過這個這個PerformanceCounter反查到Process的Instance Name，像是下面這樣：

	private string GetProcessInstanceName(int pid)
	{
		var category = new PerformanceCounterCategory("Process");

		var instances = category.GetInstanceNames();
		foreach (var instance in instances)
		{

			using (var counter = new PerformanceCounter(category.CategoryName,
				 "ID Process", instance, true))
			{
				int val = (int)counter.RawValue;
				if (val == pid)
				{
					return instance;
				}
			}
		}
		throw new ArgumentException("Invalid pid!");
	}

取得了Process的Instance Name後，CPU的使用率我們就可以透過另一個名為% Processor Time的PerformanceCounter下去取得，像是下面這樣：

	private static int GetCpuUsage(int pid)
	{
		if (!m_CounterPool.ContainsKey(pid))
		{
			m_CounterPool.Add(pid, new PerformanceCounter("Process", "% Processor Time", GetProcessInstanceName(pid)));
		}

		var lastUpdateTime = default(DateTime);

		m_UpdateTimePool.TryGetValue(pid, out lastUpdateTime);

		var interval = DateTime.Now - lastUpdateTime;

		if (interval.TotalSeconds > 1)
		{
			m_CpuUsagePool[pid] = (int)(m_CounterPool[pid].NextValue() / Environment.ProcessorCount);
		}

		return m_CpuUsagePool[pid];
	}

這邊要特別注意的是，Query PerformanceCounter的時候，必須要間隔一秒，不然會一直Query到錯誤的值。還有就是取得的值必須要除以核心數才會是我們期望的值。

為了方便重用，依慣例筆者還是稍微整理了一下擴充方法：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

public static class ProcessExtension
{
	#region Private Static Var
	private static Dictionary<int, PerformanceCounter> _counterPool;
	private static Dictionary<int, DateTime> _updateTimePool;
	private static Dictionary<int, int> _cpuUsagePool;
	#endregion


	#region Private Static Property
	private static Dictionary<int, PerformanceCounter> m_CounterPool
	{
		get
		{
			return _counterPool ?? (_counterPool = new Dictionary<int, PerformanceCounter>());
		}
	}

	private static Dictionary<int, DateTime> m_UpdateTimePool
	{
		get
		{
			return _updateTimePool ?? (_updateTimePool = new Dictionary<int, DateTime>());
		}
	}

	private static Dictionary<int, int> m_CpuUsagePool
	{
		get
		{
			return _cpuUsagePool ?? (_cpuUsagePool = new Dictionary<int, int>());
		}
	}
	#endregion


	#region Private Static Method
	private static string GetProcessInstanceName(int pid)
	{
		var category = new PerformanceCounterCategory("Process");

		var instances = category.GetInstanceNames();
		foreach (var instance in instances)
		{

			using (var counter = new PerformanceCounter(category.CategoryName,
				 "ID Process", instance, true))
			{
				int val = (int)counter.RawValue;
				if (val == pid)
				{
					return instance;
				}
			}
		}
		throw new ArgumentException("Invalid pid!");
	}

	private static int GetCpuUsage(int pid)
	{
		if (!m_CounterPool.ContainsKey(pid))
		{
			m_CounterPool.Add(pid, new PerformanceCounter("Process", "% Processor Time", GetProcessInstanceName(pid)));
		}

		var lastUpdateTime = default(DateTime);

		m_UpdateTimePool.TryGetValue(pid, out lastUpdateTime);

		var interval = DateTime.Now - lastUpdateTime;

		if (interval.TotalSeconds > 1)
		{
			m_CpuUsagePool[pid] = (int)(m_CounterPool[pid].NextValue() / Environment.ProcessorCount);
		}

		return m_CpuUsagePool[pid];
	}
	#endregion


	#region Public Static Method
	public static string GetInstanceName(this Process process)
	{
		return GetProcessInstanceName(process.Id);
	}

	public static int GetCpuUsage(this Process process)
	{
		return GetCpuUsage(process.Id);
	}
	#endregion
}

已筆者的測試範例來說，撰寫起來會像下面這樣：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication24
{
	public partial class Form1 : Form
	{
		public Form1()
		{
			InitializeComponent();
		}

		private void Form1_Load(object sender, EventArgs e)
		{
			timer1.Interval = 1000;
			lbxProcess.DisplayMember = "ProcessName";
			lbxProcess.DataSource = Process.GetProcesses();
		}

		private void lbxProcess_SelectedIndexChanged(object sender, EventArgs e)
		{
			var selectedProcess = lbxProcess.SelectedItem as Process;
			if (selectedProcess == null)
				return;

			timer1.Enabled = false;
			tbxInstanceName.Text = selectedProcess.GetInstanceName();
			tbxCPU.Text = selectedProcess.GetCpuUsage().ToString();
			timer1.Enabled = true;
		}

		private void timer1_Tick(object sender, EventArgs e)
		{
			var selectedProcess = lbxProcess.SelectedItem as Process;
			if (selectedProcess == null)
				return;

			tbxCPU.Text = selectedProcess.GetCpuUsage().ToString();
		}
	}
}

運行結果：

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