By default, `top` on Linux runs in so-called IRIX mode, while the Windows Task Manager does not. Let&#39;s say you have 4 cores:

* With IRIX mode on, 1 fully utilized core is 100% and 4 cores are 400%. 

* With IRIX mode off, 1 fully utilized core is 25% and 4 cores are 100%. 

This means that by default, `top` on Linux will show an infinite loop as ~100% and Windows will show it as ~25%, and it means exactly the same thing.

You can toggle IRIX mode while `top` is running with &lt;kbd&gt;Shift&lt;/kbd&gt;+&lt;kbd&gt;i&lt;/kbd&gt;. This will make the numbers match up. 

In my code, I deal with an array that has some entries with many objects nested inside one another, where as some do not. It looks something like the following:

    // where this array is hundreds of entries long, with a mix
    // of the two examples given
    var test = [{&#39;a&#39;:{&#39;b&#39;:{&#39;c&#39;:&quot;foo&quot;}}}, {&#39;a&#39;: &quot;bar&quot;}];

This is giving me problems because I need to iterate through the array at times, and the inconsistency is throwing me errors like so:

    for (i=0; i&lt;test.length; i++) {
        // ok on i==0, but &#39;cannot read property of undefined&#39; on i==1
        console.log(a.b.c);
    }

I am aware that I can say `if(a.b){ console.log(a.b.c)}`, but this is extraordinarily tedious in cases where there are up to 5 or 6 objects nested within one another. Is there any other (easier) way that I can have it ONLY do the console.log if it exists, but without throwing an error?

How to avoid &#39;cannot read property of undefined&#39; errors?

I have a table in `PostgreSQL 8.3` with 2 `timestamp` columns. I would like to get the difference between these `timestamps` in seconds. Could you please help me how to get this done?

    TableA
    (
      timestamp_A timestamp,
      timestamp_B timestamp
    )

I need to get something like `(timestamo_B - timestamp_A)` in seconds *(not just the difference between seconds, it should include hours, minutes etc)*.

Find difference between timestamps in seconds in PostgreSQL

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?

I have created a simple program in java:
<pre><code class="hljs language-arduino">public static void main(String[] args) throws InterruptedException {
 while (true) 
 ;
}
</code></pre>
If I run this on a Linux machine, it shows 100% CPU usage, but doesn'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'm wondering if Windows' scheduler preempt threads randomly and Linux's doesn't?

I have downloaded `apache-tomcat-7.0.35`. My JDK version is `jdk1.6.0_27`. 

How do I configure `CATALINA_HOME` as an environment variable and how do I run Tomcat server under Windows 7?

How to set CATALINA_HOME variable in windows 7?

It seems that there are two methods for templating with JSP. Including files with one of these statements 

    &lt;%@ include file=&quot;foo.html&quot; %&gt;
    &lt;jsp:include page=&quot;foo.html&quot; /&gt;

or using JSP tag files 

    // Save this as mytag.tag
    &lt;%@ tag description=&quot;Description&quot; pageEncoding=&quot;UTF-8&quot;%&gt;
    &lt;html&gt;
    &lt;head&gt;
    &lt;/head&gt;
    &lt;body&gt;
        &lt;jsp:doBody/&gt;
    &lt;/body&gt;
    &lt;/html&gt;

And in another JSP page call it with

    &lt;%@ taglib prefix=&quot;t&quot; tagdir=&quot;/WEB-INF/tags&quot; %&gt;
        
    &lt;t:mytag&gt;
        &lt;h1&gt;Hello World&lt;/h1&gt;
    &lt;/t:mytag&gt;

So which method should I use? Is one now considered deprecated or are they both valid and cover different use cases?

**Edit**

Isn&#39;t using this tag file the same as using an include?

    // Save this as product.tag
    &lt;%@ tag description=&quot;Product templage&quot; pageEncoding=&quot;UTF-8&quot;%&gt;
    &lt;%@ tag import=&quot;com.myapp.Product&quot; %&gt;
    &lt;%@ attribute name=&quot;product&quot; required=&quot;true&quot; type=&quot;com.myapp.Product&quot;%&gt;
    
    Product name: ${product.name} &lt;br/&gt;
    Quantity: ${product.quantity} &lt;br/&gt;

And call it on another JSP with

    &lt;%@ taglib prefix=&quot;t&quot; tagdir=&quot;/WEB-INF/tags&quot; %&gt;
    
    &lt;t:product&gt;
        &lt;c:forEach items=&quot;${cart.products}&quot; var=&quot;product&quot;&gt;
            &lt;t:product product=&quot;${product}&quot;/&gt;
        &lt;/c:forEach&gt;
    &lt;/t:product&gt;

That seems to me to be the very same as using an include and passing parameters to it. So are Tag Files the same as includes?

What&#39;s the difference between including files with JSP include directive, JSP include action and using JSP Tag Files?

Is it good practice to call `org.hibernate.Session.flush()` separately?

As said in `org.hibernate.Session` docs, 

&gt; Must be called at the end of a unit of work, before commiting the transaction and closing the session (depending on flush-mode, Transaction.commit() calls this method).

Could you explain the purpose of calling `flush()` explicitely if `org.hibernate.Transaction.commit()` will do it already?

Hibernate: flush() and commit()

I have a REST service built with Jersey and deployed in the AppEngine. The REST service implements the verb PUT that consumes an `application/json` media type. The data binding is performed by Jackson.


The verb consumes an enterprise-departments relation represented in JSON as 

    {&quot;name&quot;:&quot;myEnterprise&quot;, &quot;departments&quot;:[&quot;HR&quot;,&quot;IT&quot;,&quot;SC&quot;]}

On the client side, I use gson to convert the JSON representation into a java object. Then, I pass the object to my REST service and it works fine.

**Problem:**

When my JSON representation has only one item in the collection
 
    {&quot;name&quot;:&quot;myEnterprise&quot;, &quot;departments&quot;:[&quot;HR&quot;]}

 the service cannot deserialize the object.


    ATTENTION: /enterprise/enterprise: org.codehaus.jackson.map.JsonMappingException: 
    Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token at 
    [Source: org.mortbay.jetty.HttpParser$Input@5a9c5842; line: 1, column: 2

As reported by other users, the solution is to add the flag `ACCEPT_SINGLE_VALUE_AS_ARRAY` (e.g., https://stackoverflow.com/questions/14319573/jersey-can-not-deserialize-instance-of-arraylist-out-of-string). Nevertheless, I am not controlling an `ObjectMapper` because in the service side it is transparently made by Jackson.

**Question:**

Is there a way to configure the `ObjectMapper` on the service side to enable `ACCEPT_SINGLE_VALUE_AS_ARRAY`? annotations? `web.xml`?



**Code details**

Java object:

    @XmlRootElement
    public class Enterprise {
    	private String name;
    	private List&lt;String&gt; departments;
    	
    	public Enterprise() {}
    
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
        	this.name = name;
       	}
        public List&lt;String&gt; getDepartments() {
    		return departments;
    	}
    	public void setDepartments(List&lt;String&gt; departments) {
    		this.departments = departments;
    	}
    }


The REST service side:

    	@PUT
    	@Consumes(MediaType.APPLICATION_JSON)
    	@Produces(MediaType.APPLICATION_JSON)
    	@Path(&quot;/enterprise&quot;) 
       	public Response putEnterprise(Enterprise enterprise,
    			@Context HttpServletRequest req){
             ...
    	}

Client side:

    ...
    String jsonString = &quot;{\&quot;name\&quot;:\&quot;myEnterprise\&quot;, \&quot;departments\&quot;:[\&quot;HR\&quot;]}&quot;;
    Enterprise enterprise = gson.fromJson(jsonString, Enterprise.class);
    System.out.println(gson.toJson(enterprise));
    response = webResource              
               .type(MediaType.APPLICATION_JSON)
               .put(ClientResponse.class,enterprise);
    if (response.getStatus() &gt;= 400) {
            throw new RuntimeException(&quot;Failed : HTTP error code : &quot; + response.getStatus());
    }
    ...

Can not deserialize instance of java.util.ArrayList out of VALUE_STRING

I read some articles about how to use log4j.
Most of them give below code as a beginning:

     Logger logger = Logger.getLogger(&quot;com.foo.Bar&quot;);

or

     Logger logger = Logger.getLogger(XXX.class);

This will initialize the logger object.But my question is why need send the class type as a parameter? It seems when I use the logger, I don&#39;t care in which class I use it.So the Class type seems no effect to logger.
If I declare a logger as static and public, I can call this logger at another class, So what&#39;s the intention of the author to design it like this? Will the Class type bind something when I use the logger? Or I can send any Class types to the getLogger function.



Why log4j&#39;s Logger.getLogger() need pass a Class type?

I have installed **mongo-10gen mongo-10gen-server** on Linux CentOS server.

I followed the steps from [**Link**][1].

I have configured **/etc/mongod.conf** as - 

    logpath=/var/log/mongo/mongod.log
    port=27017
    dbpath=/var/lib/mongo

I have set port 27017 for mongo in **iptables**.
To start mongo I used commands - 

    service mongod start and
    mongo

It get started well, but after few days I am getting the error - 


    Tue Jan 29 08:41:54 [initandlisten] ERROR: Insufficient free space for journal files
    Tue Jan 29 08:41:54 [initandlisten] Please make at least 3379MB available in /var/lib/mongo/journal or use --smallfiles
    Tue Jan 29 08:41:54 [initandlisten]
    Tue Jan 29 08:41:54 [initandlisten] exception in initAndListen: 15926 Insufficient free space for journals, terminating
    Tue Jan 29 08:41:54 dbexit:
    Tue Jan 29 08:41:54 [initandlisten] shutdown: going to close listening sockets...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: going to flush diaglog...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: going to close sockets...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: waiting for fs preallocator...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: lock for final commit...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: final commit...
    Tue Jan 29 08:41:54 [initandlisten] shutdown: closing all files...
    Tue Jan 29 08:41:54 [initandlisten] closeAllFiles() finished
    Tue Jan 29 08:41:54 [initandlisten] journalCleanup...
    Tue Jan 29 08:41:54 [initandlisten] removeJournalFiles
    Tue Jan 29 08:41:54 [initandlisten] shutdown: removing fs lock...
    Tue Jan 29 08:41:54 dbexit: really exiting now



When I execute the command - 

    service mongod status

It gives Error - 

    mongod dead but subsys locked


Please help me to solve the problem of ***mongod dead but subsys locked*** and ***Insufficient free space for journals, terminating***


  [1]: http://docs.mongodb.org/manual/tutorial/install-mongodb-on-redhat-centos-or-fedora-linux/

Why getting error mongod dead but subsys locked and Insufficient free space for journal files on Linux?

I have been searching and tried various alternatives without success and spent several days on it now - driving me mad.

Running on Red Hat Linux with Python 2.5.2
Began using most recent Virtualenv but could not activate it, I found somewhere suggesting needed earlier version so I have used Virtualenv 1.6.4 as that should work with Python 2.6.

It seems to install the virtual environment ok
---------
    [necrailk@server6 ~]$ python virtualenv-1.6.4/virtualenv.py virtual
    New python executable in virtual/bin/python
    Installing setuptools............done.
    Installing pip...............done.

Environment looks ok
---------------------
    [necrailk@server6 ~]$ cd virtual
    [necrailk@server6 ~/virtual]$ dir
    bin  include  lib

Trying to activate
---------------------
    [necrailk@server6 ~/virtual]$ . bin/activate
    /bin/.: Permission denied.

Checked chmod
---------------------
    [necrailk@server6 ~/virtual]$ cd bin
    [necrailk@server6 bin]$ ls -l
    total 3160
    -rw-r--r--    1 necrailk biz12        2130 Jan 30 11:38 activate
    -rw-r--r--    1 necrailk biz12        1050 Jan 30 11:38 activate.csh
    -rw-r--r--    1 necrailk biz12        2869 Jan 30 11:38 activate.fish
    -rw-r--r-

Problem, so I changed it
----------------------
    [necrailk@server6 bin]$ ls -l
    total 3160
    -rwxr--r--    1 necrailk biz12        2130 Jan 30 11:38 activate
    -rw-r--r--    1 necrailk biz12        1050 Jan 30 11:38 activate.csh
    -rw-r--r--    1 necrailk biz12        2869 Jan 30 11:38 activate.fish
    -rw-r--r--    1 necrailk biz12        1005 Jan 30 11:38 activate_this.py
    -rwxr-xr-x    1 necrailk biz

Try `activate` again
--------------------
    [necrailk@server6 ~/virtual]$ . bin/activate
    /bin/.: Permission denied.

Still no joy...

How to activate virtualenv in Linux?

I normally run multiple commands with something like this:

    sleep 2 &amp;&amp; sleep 3

or

    sleep 2 ; sleep 3

but what if I want to run them both in the background from one command line command?

    sleep 2 &amp; &amp;&amp; sleep 3 &amp;

doesn&#39;t work. And neither does replacing `&amp;&amp;` with `;`

Is there a way to do it?

How do I run multiple background commands in bash in a single line?

On Linux, how can I add a directory to the $PATH so it remains persistent across different sessions?

#### Background

I&#39;m trying to add a directory to my path so it will always be in my Linux path. I&#39;ve tried:

    export PATH=$PATH:/path/to/dir

This works, however each time I exit the terminal and start a new terminal instance, this path is lost, and I need to run the export command again.

How can I do it so this will be set permanently?


How to permanently set $PATH on Linux/Unix

I am trying to use `\d` in regex in sed but it doesn&#39;t work:

    sed -re &#39;s/\d+//g&#39;

But this is working:

    sed -re &#39;s/[0-9]+//g&#39;

Why doesn&#39;t `\d` work in regular expressions in sed?

I have already seen 
http://dev.mysql.com/doc/refman/4.1/en/mysql-config-wizard-file-location.html

https://stackoverflow.com/questions/2482234/how-to-know-mysql-my-cnf-location

and 

http://dev.mysql.com/doc/refman/5.1/en/option-files.html

But I am still stuck with the ages old question!
&quot;Where is my my.ini&quot;
I am using windows server 2008 with mysql 5.5.28. I installed the service using mysqld --install and I am able to use the mysql server using sqlyog. But unfortunately I am not able to find my.ini in `installation directory` or not in `c:\` neither in `c:\windows` nor in `data_dir` query `show variables like &quot;mysql_home&quot;` returned nothing as well.

Any suggestions?



MySQL my.ini location

There has been variants of this question asked for generations, but despite writing some quite complicated Windows scripts, I can&#39;t seem to find out how to make them actually silent.

The following is an excerpt from one of my current scripts:

    @ECHO OFF
    SET scriptDirectory=%~dp0
    COPY %scriptDirectory%test.bat %scriptDirectory%test2.bat
    FOR /F %%f IN (&#39;dir /B &quot;%scriptDirectory%*.noext&quot;&#39;) DO (
	del &quot;%scriptDirectory%%%f&quot;
	)
    ECHO

The result of this is:

    C:\Temp&gt; test.bat
            1 file(s) copied.
    File Not Found
    Echo is off.

    C:\Temp&gt;

Whereas the &quot;1 file(s) copied.&quot; is just annoying, the &quot;File Not Found&quot; makes the user think that something has gone wrong (which it hasn&#39;t - no files is fine).


How do I make a Windows batch script completely silent?

I am creating a very large project (a few thousand lines) and so would rather not use Notepad++. An IDE would make it so much easier. I have experience with Microsoft Visual Studio and love it. Is there some easy way to use Cygwin&#39;s GCC from within Microsoft Visual Studio? 

Alternately, are there any other good Windows IDEs for GCC besides NetBeans and Eclipse? (I hate both of them with a passion.)

How to use GCC with Microsoft Visual Studio?

This is my first time working with Node.js and I ran into this problem:

I have started a Node server through the plugin of an IDE. Unfortunately, I cannot use the IDE&#39;s terminal. So I tried to run the script from the command line.

This is the problem - I am using the Express module and my app is listening some port (8080). When I start the app from the command line, it throws this error:

    events.js:71
        throw arguments[1]; // Unhandled &#39;error&#39; event
                       ^
    Error: listen EADDRINUSE
        at errnoException (net.js:770:11)
        at HTTPServer.Server._listen2 (net.js:910:14)
        at listen (net.js:937:10)
        at HTTPServer.Server.listen (net.js:986:5)
        at Object.&lt;anonymous&gt; (C:\xampp\htdocs\node\chat\app.js:5:5)
        at Module._compile (module.js:449:26)
        at Object.Module._extensions..js (module.js:467:10)
        at Module.load (module.js:356:32)
        at Function.Module._load (module.js:312:12)
        at Module.runMain (module.js:492:10)

Even though I am not very sure what this error could be I assumed that it&#39;s because the app is listening on a port which is already in use. So I did:

    netstat -an

I can see  

    TCP    0.0.0.0:8080           0.0.0.0:0              LISTENING

It&#39;s because the Node server is already started when I tried to start it from the IDE.

So I want to know, how can I stop all server instances? Also if you can tell me how to detect what&#39;s running on a port and kill it.

    

stop all instances of node.js server

I need to get the date in YYYYMMDD format in batch file. 

I am doing this using :

    set mydate=%date:~6,4%%date:~3,2%%date:~0,2%
    echo %mydate%

I need it to be consistent across system, even on changing the time settings.

Please advise.

Get Date in YYYYMMDD format in windows batch file

I am new to Android SDK/API environment. It&#39;s the first I am trying to draw a plot/chart. I tried running different kinds of sample codes on the emulator using 3 different free libraries, nothing is showing on the layout screen. The logcat is repeating the following message:

&lt;pre&gt;
 W/Trace(1378): Unexpected value from nativeGetEnabledTags: 0
 I/Choreographer(1378): Skipped 55 frames!  The application may be doing too much work on its main thread. 
&lt;/pre&gt;
The problem didn&#39;t persist and the chart worked when I ran a sample code pertaining to an evaluation copy of a licensed library. 


The application may be doing too much work on its main thread

this is a passage from JavaDoc regarding `ConcurrentHashMap`. It says retrieval operations generally do not block, so may overlap with update operations. Does this mean the `get()` method is not thread safe?


&gt; &quot;However, even though all operations are thread-safe, retrieval
&gt; operations do not entail locking, and there is not any support for
&gt; locking the entire table in a way that prevents all access. This class
&gt; is fully interoperable with Hashtable in programs that rely on its
&gt; thread safety but not on its synchronization details.
&gt; 
&gt; Retrieval operations (including get) generally do not block, so may
&gt; overlap with update operations (including put and remove). Retrievals
&gt; reflect the results of the most recently completed update operations
&gt; holding upon their onset.&quot;

Is ConcurrentHashMap totally safe?

For something simple like a counter if multiple threads will be increasing the number. I read that mutex locks can decrease efficiency since the threads have to wait. So, to me, an atomic counter would be the most efficient, but I read that internally it is basically a lock? So I guess I&#39;m confused how either could be more efficient than the other. 

Which is more efficient, basic mutex lock or atomic integer?

Compared to the preceding code [for class RulyCanceler][1], I wanted to run code using  `CancellationTokenSource`.

How do I use it as mentioned in [Cancellation Tokens][2], i.e. without throwing/catching an exception?   Can I use the `IsCancellationRequested` property?  

I attempted to use it like this:  

    cancelToken.ThrowIfCancellationRequested();

and

    try
    {
      new Thread(() =&gt; Work(cancelSource.Token)).Start();
    }
    catch (OperationCanceledException)
    {
      Console.WriteLine(&quot;Canceled!&quot;);
    }

but this gave a run-time error on `cancelToken.ThrowIfCancellationRequested();` in method `Work(CancellationToken cancelToken)`:  

    System.OperationCanceledException was unhandled
      Message=The operation was canceled.
      Source=mscorlib
      StackTrace:
           at System.Threading.CancellationToken.ThrowIfCancellationRequested()
           at _7CancellationTokens.Token.Work(CancellationToken cancelToken) in C:\xxx\Token.cs:line 33
           at _7CancellationTokens.Token.&lt;&gt;c__DisplayClass1.&lt;Main&gt;b__0() in C:\xxx\Token.cs:line 22
           at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
           at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
           at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
           at System.Threading.ThreadHelper.ThreadStart()
      InnerException:


The code that I successfully ran caught the OperationCanceledException in the new thread:

    using System;
    using System.Threading;
    namespace _7CancellationTokens
    {
      internal class Token
      {
        private static void Main()
        {
          var cancelSource = new CancellationTokenSource();
          new Thread(() =&gt;
          {
             try
             {
               Work(cancelSource.Token); //).Start();
             }
             catch (OperationCanceledException)
             {
                Console.WriteLine(&quot;Canceled!&quot;);
             }
             }).Start();
          
          Thread.Sleep(1000);
          cancelSource.Cancel(); // Safely cancel worker.
          Console.ReadLine();
        }
        private static void Work(CancellationToken cancelToken)
        {
          while (true)
          {
            Console.Write(&quot;345&quot;);
            cancelToken.ThrowIfCancellationRequested();
          }
        }
      }
    }

  [1]: http://www.albahari.com/threading/part3.aspx#_Safe_Cancellation
  [2]: http://www.albahari.com/threading/part3.aspx#_Cancellation_Tokens




How to use the CancellationToken property?

I was studying the python threading and came across [`join()`](http://docs.python.org/2/library/threading.html#threading.Thread.join).

The author told that if thread is in daemon mode then i need to use `join()` so that thread can finish itself before main thread terminates.

but I have also seen him using `t.join()` even though `t` was not `daemon`

example code is this


    import threading
    import time
    import logging
    
    logging.basicConfig(level=logging.DEBUG,
                        format=&#39;(%(threadName)-10s) %(message)s&#39;,
                        )
    
    def daemon():
        logging.debug(&#39;Starting&#39;)
        time.sleep(2)
        logging.debug(&#39;Exiting&#39;)
    
    d = threading.Thread(name=&#39;daemon&#39;, target=daemon)
    d.setDaemon(True)
    
    def non_daemon():
        logging.debug(&#39;Starting&#39;)
        logging.debug(&#39;Exiting&#39;)
    
    t = threading.Thread(name=&#39;non-daemon&#39;, target=non_daemon)
    
    d.start()
    t.start()
    
    d.join()
    t.join()


i don&#39;t know what is use of `t.join()` as it is not daemon and i can see no change even if i remove it




What is the use of join() in Python threading?

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 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?

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

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

Content Type	Original Author	Original Content on Stackoverflow
Question	Maniek	View Question on Stackoverflow
Solution 1 - Java	that other guy	View Answer on Stackoverflow

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