I&#39;d like to automatically kill a command after a certain amount of time.  I have in mind an interface like this:

    % constrain 300 ./foo args

Which would run &quot;./foo&quot; with &quot;args&quot; but automatically kill it if it&#39;s still running after 5 minutes.

It might be useful to generalize the idea to other constraints, such as autokilling a process if it uses too much memory.

Are there any existing tools that do that, or has anyone written such a thing?

ADDED: Jonathan&#39;s solution is precisely what I had in mind and it works like a charm on linux, but I can&#39;t get it to work on Mac OSX.  I got rid of the SIGRTMIN which lets it compile fine, but the signal just doesn&#39;t get sent to the child process.  Anyone know how to make this work on Mac?

[Added: Note that an update is available from Jonathan that works on Mac and elsewhere.]

Command line command to auto-kill a command after a certain amount of time

I have a Java Application (web-based) that at times shows very high CPU Utilization (almost 90%) for several hours. Linux `TOP` command shows this. On application restart, the problem goes away.

***So to investigate***:

I take Thread Dump to find what threads are doing. Several Threads are found in `&#39;RUNNABLE&#39;` state, some in few other states. On taking repeated Thread Dumps, i do see some threads that are always present in `&#39;RUNNABLE&#39;` state. So, they appear to be the culprit.

But I am unable to tell for sure, which Thread is hogging the CPU or has gone into a infinite loop (thereby causing high CPU util).

Logs don&#39;t necessarily help, as the offending code may not be logging anything.

***How do I investigate - What part of the application or what-thread is causing High CPU Utilization? - Any other ideas?*** 


High CPU Utilization in java application - why?

Of late, I&#39;m becoming more health oriented when constructing my program, I have observed that most of programs take 2 or 3 minutes to execute and when I check on the task scheduler, I see that they consume 100% of CPU usage, can I limit this usage programatically in code? This will certainly enable me to run multiple programs at a given time.

Thanks,
Nidhi

How can I programmatically limit my program&#39;s CPU usage to below 70%?

I want to get the overall total CPU usage for an application in C#. I&#39;ve found many ways to dig into the properties of processes, but I only want the CPU usage of the processes, and the total CPU like you get in the TaskManager.

How do I do that?

How to get the CPU Usage in C#?

Recently my server CPU has been going very high.

CPU load averages 13.91 (1 min) 11.72 (5 mins) 8.01 (15 mins) and my site has only had a slight increase in traffic.

After running a top command, I saw MySQL was using 160% CPU!

Recently I&#39;ve been optimizing tables and I&#39;ve switched to persistent connections.  Could this be causing MySQL to use high amounts of CPU?

MySQL high CPU usage

I want to get the CPU and memory usage of a single process on Linux - I know the PID.  Hopefully, I can get it every second and write it to a CSV using the &#39;watch&#39; command.  What command can I use to get this info from the Linux command-line?

Retrieve CPU usage and memory usage of a single process on Linux?

I have created a simple program in java:

    public static void main(String[] args) throws InterruptedException {
        while (true) 
            ;
    }

If I run this on a Linux machine, it shows 100% CPU usage, but doesn&#39;t cause the OS to appear slow.  However, if I run the exact same code on Windows, it only shows about 20% CPU usage.

I am using Oracle JRE on Windows and OpenJDK 6 on Linux.

I&#39;m wondering if Windows&#39; scheduler preempt threads randomly and Linux&#39;s doesn&#39;t?

Why does “while(true)” without “Thread.sleep” cause 100% CPU usage on Linux but not on Windows?

The emulator qemu-system-i386.exe cpu usage almost constantly running between 7~9

Android studio 2.1
Android SDK Tools: 25.1.3
Host Operating System: Windows 7 - i7 2630QM - 8GB Ram
Intel x86 Atom System Image installed

No matter what setting i change in the emulator like: emulated performance, multi-core CPU, x86-64 image, always the same thing

It is really annoying fan always on

Anyone had a fix for this issue?



High CPU usage with Android emulator (qemu-system-i386.exe)

On Ice Cream Sandwich, an option in the Developer Options is &quot;Show CPU Usage&quot;, which adds an overlay on the screen (see screenshot below). 

My question is, how do I read the data ? I guessed that the package names are the process currently actives, but what does the red and green bars behind mean ? 
Also what are the 3 numbers on top of the packages ? 

![enter image description here][1]


  [1]: http://i.stack.imgur.com/oU32V.png

How to read the Stock CPU Usage data

I want to programmatically [in C] calculate CPU usage % for a given process ID in Linux.

How can we get the realtime CPU usage % for a given process?

To make it further clear:

 - I should be able to determine the CPU usage for the provided processid or process.  
 - The process need not be the child process.  
 - I want the solution in &#39;C&#39; language.

How to calculate the CPU usage of a process by PID in Linux from C?

I&#39;ve noticed Android Studio (when running) uses greater than 100% CPU at all times, even when it appears there are no background processes that the IDE is running (indexing, etc). I might suspect this were something specific to my box, but some fellow developers are encountering this as well.

Often times the CPU usage is in the high 100s or mid 200s (see screenshots below). Has anyone encountered this as well? If so, are there any strategies or options within the IDE to correct this intensive use of system resources?

![enter image description here][1]


![enter image description here][2]


  [1]: http://i.stack.imgur.com/k79Yk.png
  [2]: http://i.stack.imgur.com/KIQOd.png

Android studio using &gt; 100% CPU at all times - no background processes appear to be running

I&#39;ve recently updated VS2013 to Update 1 and since then VS takes CPU usage to 25% (on a 4 cores intel i5 cpu) permanently even though it&#39;s supposed to be idle. I thought it has some unfinished background processes so I left it running for a while but it keeps using the cpu when it&#39;s supposed to be idle.

Are you getting a similar behaviour after updating?

**Edit 1**: I&#39;m using git and python tools for vs, so there might be some conflicts after Update 1.

**Edit 2**: The git integration in `VS2013` is buggy. I ran a profiler on `devenv.exe` and `git2-msvstfs.dll` takes most of cpu usage although it should be idle. I sent a failure notice to MS. If you have the same problem please vote for this: http://connect.microsoft.com/VisualStudio/feedback/details/844616/vs2013-update-1-cpu-usage-not-normal

![enter image description here][1]

**Edit 3**: Update 2 has been recently released. This bug was fixed in VS2013 Update 2.

  [1]: http://i.stack.imgur.com/Rekey.png

**Edit 4**: Updates 3 &amp; 4 were released and CPU usage goes crazy due to multiple causes (not only git dll module). Disabling `Browser Link` as in one of the below answers seems to fix the problem.

VS2013 permanent CPU usage even though in idle mode

On my desktop, I have a little widget that tells me my current CPU usage. It also shows the usage for each of my two cores. 

I always wondered, how does the CPU calculate how much of its processing power is being used? Also, if the CPU is hung up doing some intense calculations, how can it (or whatever handles this activity) examine the usage, without getting hung up as well?


How is CPU usage calculated?

My SQL Server CPU has been at around 90% for the most part of today.

I am not in a position to be able to restart it due to it being in constant use.

Is it possible to find out what within SQL is causing such a CPU overload?

I have run SQL Profiler but so much is going on it&#39;s difficult to tell if anything in particular is causing it.

I have run sp_who2 but am not sure what everything means exactly and if it is possible to identify possible problems in here.

To pre-empt any &quot;it&#39;s probably just being used a lot&quot; responses, this has only kicked in today from perfectly normal activitly levels.

I&#39;m after any way of finding what is causing CPU grief within SQL.

How do I find out what is hammering my SQL Server?

It&#39;s a question which has been asked many times, however there is no well supported answer I could find.

Many people suggest the use of top command, but if you run top once (because you have a script for example collecting Cpu usage every 1 second) it will always give the same Cpu usage result ([example 1][1], [example 2][2]).

A more accurate way to calculate CPU usage, is by reading the values from `/proc/stat`, but most of the answers use only the first 4 fields from `/proc/stat` to calculate it (one example [here][2]).

`/proc/stat/` has 10 fields per CPU core as of Linux kernel 2.6.33!

I also found this https://stackoverflow.com/questions/5514119/accurately-calculating-cpu-utilization-in-linux-using-proc-stat question which is pointing out the same issue, -that most other questions only take into consideration 4 out of the many fields- but still the answer given here starts with &quot;I think&quot; (not certain), and except that, it is only concerned about the first 7 fields (out of 10 in `/proc/stat/`)

[This][3] perl script uses all of the fields to calculate the CPU usage, which again I do not think is correct after some further investigation.

After taking a quick look into the kernel code [here][4], it looks like, for example, `guest_nice` and `guest fields` are always increasing together with `nice` and `user` (so they should not be included in the cpu usage calculation, since they are included in `nice` and `user` fields already)

    /*
     * Account guest cpu time to a process.
     * @p: the process that the cpu time gets accounted to
     * @cputime: the cpu time spent in virtual machine since the last update
     * @cputime_scaled: cputime scaled by cpu frequency
     */
    static void account_guest_time(struct task_struct *p, cputime_t cputime,
    			       cputime_t cputime_scaled)
    {
    	u64 *cpustat = kcpustat_this_cpu-&gt;cpustat;
    
    	/* Add guest time to process. */
    	p-&gt;utime += cputime;
    	p-&gt;utimescaled += cputime_scaled;
    	account_group_user_time(p, cputime);
    	p-&gt;gtime += cputime;
    
    	/* Add guest time to cpustat. */
    	if (task_nice(p) &gt; 0) {
    		cpustat[CPUTIME_NICE] += (__force u64) cputime;
    		cpustat[CPUTIME_GUEST_NICE] += (__force u64) cputime;
    	} else {
    		cpustat[CPUTIME_USER] += (__force u64) cputime;
    		cpustat[CPUTIME_GUEST] += (__force u64) cputime;
    	}
    }

So to sum up, what is an accurate way to calculate the CPU usage in Linux and which fields should be considered in the calculations and how (which fields are attributed to the idle time and which fields to non-idle time)?


  [1]: https://unix.stackexchange.com/questions/69185/getting-cpu-usage-same-every-time
  [2]: https://unix.stackexchange.com/questions/27076/how-can-i-receive-top-like-cpu-statistics-from-the-shell
  [3]: https://gist.github.com/creaktive/781248
  [4]: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/sched/cputime.c?h=v4.8#n169

Accurate calculation of CPU usage given in percentage in Linux?

How can I get the **CPU** and **Memory usage** of a particular process using the .NET `PerformanceCounter` class? And also what is the difference between 

`Processor\% Processor Time` and `Process\% Processor Time`?

I am a bit confused between these two.

What is the correct Performance Counter to get CPU and Memory Usage of a Process?

Is there any API by which we can get CPU or Memory usage of android?

I have tried one code as below:

    package com.infostretch.mainactivity;

    import java.io.BufferedReader;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.io.InputStreamReader;

    public class CPULoad 
    {
        long total = 0;
        long idle = 0;

        float usage = 0;

        public CPULoad()
        {
            readUsage();
        }

        public float getUsage()
        {
            readUsage();
            return usage;
        }

        private void readUsage()
        {
            try
            {
                BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(&quot;/proc/stat&quot;)), 1000);
                String load = reader.readLine();
                reader.close();

                String[] toks = load.split(&quot; &quot;);

                long currTotal = Long.parseLong(toks[2]) + Long.parseLong(toks[3]) + Long.parseLong(toks[4]);
                long currIdle = Long.parseLong(toks[5]);

                this.usage = (currTotal - total) * 100.0f / (currTotal - total + currIdle - idle);
                this.total = currTotal;
                this.idle = currIdle;
            }
            catch(IOException ex)
            {
                ex.printStackTrace();
            }
        }
    }

Is this the correct way to do it?

Get Memory Usage in Android

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&#39;t show any attack in the logs.  I&#39;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&#39;s desktop and read and write some files.  So because of that I changed its application pool -&gt; identity (Process Model) to local system, and I don&#39;t know if it is related with the CPU usage or not.


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

I&#39;ve developed some web-based applications till now using PHP, Python and Java. But some fundamental but very important questions are still beyond my knowledge, so I made this post to  get help and clarification from you guys.

Say I use some programming language as my backend language(PHP/Python/.Net/Java, etc), and I deploy my application with a web server(apache/lighttpd/nginx/IIS, etc). And suppose at time T, one of my page got 100 simultaneous requests from different users. So my questions are:

 1. How does my web server handle such 100 simultaneous requests? Will web server generate one process/thread for each request? (if yes, process or thread?)
 2. How does the interpreter of the backend language do? How will it handle the request and generate the proper html? Will the interpreter generate a process/thread for each request?(if yes, process or thread?) 
 3. If the interpreter will generate a process/thread for each request, how about these processes(threads)? Will they share some code space? Will they communicate with each other? How to handle the global variables in the backend codes? Or they are independent processes(threads)? How long is the duration of the process/thread? Will they be destroyed when the request is handled and the response is returned?
 4. Suppose the web server can only support 100 simultaneous requests, but now it got 1000 simultaneous requests. How does it handle such situation? Will it handle them like a queue and handle the request when the server is available? Or other approaches?
 5. I read some articles about Comet these days. And I found long connection may be a good way to handle the real-time multi-users usecase. So how about long connection? Is it a feature of some specific web servers or it is available for every web server? Long connection will require a long-existing interpreter process?

---

EDIT: 
Recently I read some articles about CGI and fastcgi, which makes me know the approach of fastcgi should be a typical approach to hanlde request.

&gt; the protocol multiplexes a single transport connection between several independent FastCGI requests. This supports applications that are able to process concurrent requests using event-driven or multi-threaded programming techniques.

Quoted from [fastcgi spec][1], which mentioned *connection* which can handle several requests, and can be implemented in mutli-threaded tech. I&#39;m wondering this *connection* can  be treated as *process* and it can generate several *threads* for each request. If this is true, I become **more** confused about how to handle the shared resource in each thread?

P.S thank Thomas for the advice of splitting the post to several posts, but I think the questions are related and it&#39;s better to group them together.

Thank S.Lott for your great answer, but some answers to each question are too brief or not covered at all. 

Thank everyone&#39;s answer, which makes me closer to the truth.

  [1]: http://www.fastcgi.com/devkit/doc/fcgi-spec.html &quot;fastcgi spec&quot;

All Cpu Usage Solutions on Gang of Coders

Total of 19 Cpu Usage Solutions