How prevent CPU usage 100% because of worker process in iis

Question

My CPU usage is 100% most of the the time in Windows Server 2008-R2 with my own vps, vmware, quad core, and 4GB Ram. When I open windows Task Manager and go to the resource monitor I see that 100% usage is because of workerprocess.exe. I have 3 websites in my IIS.

• How can I figure out which web site causes that usage
• How can I limit it to 80% usage of CPU?
• Could it be a DDOS attack?
• Is there any way to prevent DDOS?

I installed eset-nod32 on my vps, but it doesn't show any attack in the logs. I've tried searching about IIS and preventing DDOS, and just found an extension for banning IP addresses, but how can I find which IP address are generating traffic?

The web site is written in ASP.NET and C#. How can I determine what is happening on that web site and which lines of codes are causing that cpu usage?

Also, one of my web sites should access administrator's desktop and read and write some files. So because of that I changed its application pool -> identity (Process Model) to local system, and I don't know if it is related with the CPU usage or not.

Answer 1

Well, this can take long time to figure out. Few points to narrow it down:

• Identify what is killing the CPU. I recommend Process Explorer http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
• Identify what AppPool is causing this
• Fix your code

Answer 2

Diagnosing

In terms of diagnosing what App Pool is causing trouble, you can:

1. Select the server
2. Go to IIS > Worker Processes

This should bring up a menu like this so you can determine which App Pool is running amok.

From there you can simply restart the the app pool and 9 times out of 10 that will fix any immediate issues you're having.

Treating

Unless you run some sort of controversial business, this is probably not a DDOS attack. It's likely that some code is just hanging because it couldn't get through to another server or got stuck in a loop or mis-allocated resources or your app pool just hasn't been recycled in a while.

You can deal with this problem programmatically without having to manually identify, log in, and recycle the app pool. Just configure the CPU property on your App Pool. You can have it kill (and automatically restart) your process anytime you reach a CPU threshold for a certain amount of time.

In your case, if you want it to restart at 80%, you can right click on the app pool and go to Advanced Settings and apply the following configurations:

NOTE: As kraken101 pointed out, different IIS GUIs have treated this differently over time. While the config value is always in 1/1000 of a %, sometimes the GUI takes the whole percent.

You can add this to your config section like this:

<applicationPools>
   <add name="DefaultAppPool">
     <cpu limit="80000" action="KillW3wp" resetInterval="00:01:00" />
   </add>
</applicationPools>

Alternatively, you could script it with Powershell's WebAdministration Module like this:
^{(*make sure web-scripting-tools is enabled)}

Import-Module WebAdministration

$appPoolName = "DefaultAppPool"
$appPool = Get-Item "IIS:\AppPools\$appPoolName"
$appPool.cpu.limit = 80000
$appPool.cpu.action = "KillW3wp"
$appPool.cpu.resetInterval = "00:01:00"
$appPool | Set-Item

Preventing

The steps above will help fix some things once they've broken, but won't really solve any underlying issues you have.

Here are some resources on doing performance monitoring:

• Troubleshooting High CPU in an IIS 7.x Application Pool
• MSDN - Performance Tuning and Monitoring
• IIS Extension - Web Performance Monitor
• Troubleshooting Failed Requests Using Tracing
• PerfMonitor
• Log Parser

Answer 3

There are a lot of reasons that you can be seeing w3wp.exe high CPU usage. I have selected six common causes to cover.

1. High error rates within your ASP.NET web application
2. Increase in web traffic causing high CPU
3. Problems with application dependencies
4. Garbage collection
5. Requests getting blocked or hung somewhere in the ASP.NET pipeline
6. Inefficient .NET code that needs to be optimized

Answer 4

Use PerfMon to collect data and DebugDiag to analyse.

Found this link while searching for similar issue.

http://www.iis.net/learn/troubleshoot/performance-issues/troubleshooting-high-cpu-in-an-iis-7x-application-pool

Answer 5

I was facing the same issues recently and found a solution which worked for me and reduced the memory consumption level upto a great extent.

Solution:

First of all find the application which is causing heavy memory usage.

You can find this in the Details section of the Task Manager.

Next.

1. Open the IIS manager.
2. Click on Application Pools. You'll find many application pools which your system is using.
3. Now from the task manager you've found which application is causing the heavy memory consumption. There would be multiple options for that and you need to select the one which is having '1' in it's Application column of your web application.
4. When you click on the application pool on the right hand side you'll see an option Advance settings under Edit Application pools. Go to Advanced Settings. 5.Now under General category set the Enable 32-bit Applications to True
5. Restart the IIS server or you can see the consumption goes down in performance section of your Task Manager.

If this solution works for you please add a comment so that I can know.

Answer 6

If it is not necessary turn off 'Enable 32-bit Applications' from your respective application pool of your website.

This worked for me on my local machine

Answer 7

Use procmon to define your problem.

Answer 8

I recently had this problem myself, and once I determined which AppPool was causing the problem, the only way to resolve the issue was remove that app pool completly and create a new one for the site to use.