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See what's runnng and solve problems with Activity Monitor

Activity Monitor is probably regarded by many Mac users as a bit techy and geeky, and only really useful for experts that like to tinker with the inner workings of the operating system. However, it is actually quite an interesting and useful tool that can be used by almost anyone. OK, you do need a little knowledge, but not that much and everyone should take a good look at this utility because it can help you to solve problems when your Mac isn't working quite as well as it should be.

To start Activity Monitor, go to the Applications/Utilities folder in Finder and then double click it. It looks a bit scary at first with its long list of meaningless items, but all that it does is to show what OS X is running.

Look down the Process Name column. A process could be an application that you have started and are using, like iPhoto, iTunes and so on, or it could be something that OS X is running in the background, like the Dock. You don't have to explicity run the Dock each time you start the Mac and OS X does it automatically so that it is available all the time. OS X runs a lot of things in the background without your knowledge and many have obscure names that mean very little. The Dock is an obvious one, but you will see many items that mean nothing to you. Don't worry about this though because we can filter them out or simply ignore the ones that don't interest us.

In the toolbar at the top of the window is a pop-up menu that enables you to filter the items in the list. Click it and select Windowed Processes. This displays a list of applications that have windows. Activity Monitor and Finder are listed, plus any other programs that you have started. Start another application, like Address Book, iCal or something and you will see that it is added to the list of Windowed Processes.

Apple Mac OS X Activity Monitor

Activity Monitor's % CPU column
There are several columns of information and one that is often useful is % CPU. This shows how much of the processor's attention the process requires. You will find that most applications have a small % CPU figure and this is perfectly normal. When they are not actively being used, such as when they are minimised to the Dock, they might use less than 5% or even less than 1%. When you are using an application, it might rise to 20, 40 or even 60% depending on what it is doing. This is normal.

What Activity monitor is useful for is detecting abnormal behaviour. This might be an application that is using 90 to 100% of the CPU. Sometimes applications get stuck in a loop and tie up the processor doing lots of repetitive or pointless calculations, but never actually getting anywhere. The whole Mac slows down to a crawl because this app ties up the processor and doesn't let other apps get any CPU time to run.

Run Activity Monitor and check the % CPU column whenever the Mac is performing badly or stranglely. If there's an application using too much processor time then switch to that app and close it. Restart it afterwards and it will probably be OK. What if it won't quit, perhaps because it's frozen? in this case you can select the app in Activity Monitor and click the Quit Process button to forcibly end it. It's a bad idea to close applications this way because files or documents you may have open in the app could be lost or corrupted, so always try to quit an app from within the app rather than force quit in Activity Monitor. Sometimes though, you just don't have any choice.

We have seen how the pop-up menu in the toolbar can be used to display only windowed processes, which are those that you start yourself like iPhoto, Address Book and so on. There are many more processes, so click the pop-up menu and select All Processes. This displays a long list of items, many of which have strange names that mean very little to most people. However, it is the best view to use because sometimes things go wrong not with the applications that you can see on the screen (windowed processes), but processes that OS X is running in the background.

If you see a process that's using 100% of the CPU for an extended period of time (short bursts of 100% activity are normal), or close to 100%, it's quite likely that there is something wrong with it. Although it is possible to select the item and click the Quit Process button, if you don't know what the item is, it could make the system unstable. The best solution is to shut down the Mac and restart. Return to Activity Monitor afterwards and check that everything is OK.

If a process in Activity Monitor consistently monopolises the CPU then there is a fault somewhere. You should Google the process name and find out what it is and what it does. If you're having a problem with it, then it is quite likely that someone else has also had a problem with it and there may be a solution online.

Activity Monitor's Real Memory and Virtual Memory columns
The Real Memory (it may say Real Mem) is the amount of physical memory that a process (a windowed program like iPhoto or a background task like the Dock) is using. Clicking the heading sorts the processes into order with the biggest first and clicking again sorts with the smallest first.

Processes should not use excessive amounts of memory and any that uses a lot might be buggy. Any process that shows increasing memory requirements is suspect too.

There's not a lot you can do about apps that use too much memory, apart from closing them and starting them again, or seeking a newer version or update on the internet. Activity Monitor at least tells you which app is the problem though.

Computers store temporary data on the disk and because there is a huge amount of disk space compared to memory space, the disk is used as an extention to memory. It's slower than real RAM, but there is tons of it, so it's worth using. It's not possible to say how much virtual memory apps should use because it depends on the app and how much real memory is available. Just watch out for apps that use excessive amounts or for apps whose requirements rise without limit. This is an indication of a bug in the program. Quit the application if it's a regular windowed program and restart it, restart your Mac, or look for a newer version or bug fix from the supplier.

Activity Monitor's hidden columns
Activity Monitor shows several columns of information, but these aren't the only ones that are available. Some are hidden. Select View, Columns and you will see several more that you can enable. They might not mean anything unless you are a technical expert though.

Activity Monitor's bottom panel
There are five tabs at the bottom: CPU, System Memory, Disk Activity, Disk Usage and Network.

The CPU tabs shows the amount of processor activity by programs you have launched yourself (% User) like iPhoto, the amount of activity by the system (% System) such as all those background tasks that OS X performs when it is running, and the amount of time the processor is idle. CPU activity should not be 100% for prolonged periods and this would indicate a fault with an application or process. There are mini charts that show the activity on each processor core and if you double click them they open in a separate pop-up window. You can minimise Activity Monitor and leave this mini window open to monitor CPU activity.

System Memory has been covered in detail here so take a look at that article if you want to know what things like Free, Wired, Active and other items are.

Disk Activity shows the data read from and written to the disk. Whether it is high or low depends on the applications you are running and processing a video clip, for example, could result in a lot of disk activity that is quite normal. A word processor on the other hand, hardly uses the disk. High disk activity when you aren't running any applications or when running apps that shouldn't actually use the disk much can indicate a problem. You really need to use your own judgement here.

Disk Usage is simple and it just tells you how much disk space is used and the amount that is free. If the amount of free space is below 10Gb you need to think about adding a USB disk drive and moving some of your files over to it. Big files like video clips, music and digital photographs can be placed on external drives to free up internal space. OS X is faster and more effecient when it has lots of disk space to work with.

The Network tab is useful for watching network and internet activity. You can see the amount of data sent and received since the Mac was switched on and this could be useful for monitoring your bandwidth. Many ISPs will restrict internet access and lower your speed if you download/upload too much data at peak times of the day, or they might give you a monthly allowence and limit you if you go over it. It's a pity you can't see weekly or monthly totals, but it is still very useful.

Minimise Activity Monitor
When you run an application its icon is added to the Dock at the bottom of the screen. These icons are normally static images, but not Activity Monitor. Select View, Dock Icon and you can choose whether to show CPU activity, metwork usage, memory usage, or disk activity. This feature enables you to monitor your Mac without having the Activity Monitor window cluttering up the desktop. The Network Activity option is a useful one because it shows a live chart of the internet activity and you can monitor the progress of a download, see whether it has stalled, check that internet applications are actually working, and so on.

Set the update frequency
You can change how often the information displayed by Activity Monitor is updated on the View menu. The program itself uses the processor, so very frequent updates could have a slight detrimental effect on performance. It usually isn't necessary to have the updates set to 0.5s and 2s or even 5s is fine.

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