Windows Vista Super Fetch

All progress happens with a reason.

For instance, many modern software applications and interactive games are using more and more elaborate graphics; which is why 3D graphics cards and associated technologies are progressing so rapidly.

But what is the RAM good for?

How Does Windows SuperFetch Work?

What many users do not realize is that RAM isn't used only to "load programs". A lot of things are present in RAM. When you are writing a Word document, for instance, parts of the document, or even the entire document, are loaded in RAM, and written back to the computers hard drive when you save the file.

This is a technique known as 'caching'. It is convenient for the operating system to preload pieces of data that are accessed very frequently. RAM is so much faster than your computer's hard drive, so the data stored in RAM can be read in almost no time at all.

So would it not seem sensible therefore to pre-load applications you use on a regular basis (for instance your email application) into your computers RAM when it starts up?

Well Microsoft introduced this concept in Windows XP Service Pack 2, and called it "prefetching" because it did just that; it pre-fetched large chunks of data into RAM and so improved system boot time and application start-up performance.

But Windows Vista goes a BIG step further with this concept of memory management and enhances the prefetching approach from Windows XP SP2, with historical information usage and proactive memory management. It also includes specific scenario support for hibernation, standby and Fast User Switching (FUS), giving this technology a very important role within Windows Vista.

Welcome to Super Fetch!

Essentially, SuperFetch is used by Windows Vista to manage memory resource usage, so as to provide a better experience for the user.

SuperFetch continuously monitors the user's actions, and keeps track of those files and applications that are used more often. Once enough data has been gathered to draw conclusions, these files and applications are loaded to RAM. When the user requests them, they are already in RAM and can be accessed much faster. The performance improvement is indeed noticeable, especially in terms of loading times.

My personal recommendation is to have at least 1.5 Gb of RAM on any installation of Windows Vista, as SuperFetch really is such a useful service and I want to give it as much space as possible in which to work.

As you may have guessed, SuperFetch uses very advanced predictive algorithms. According to Eric Horvitz, who worked on these algorithms along with a team of Microsoft researchers, SuperFetch can safely predict the next three applications a user will launch at any point. Based on these predictions, SuperFetch can manage background tasks, such as disk defragmenting or Windows Defender (AntiSpyware software).

When the computer is idle, these tasks are given a higher priority. When the user is working, a lower task is given to them, so that they do not affect the system's performance.

SuperFetch is one of the most notable innovations in the Windows world as it significantly improves Windows Vista's performance. Some of the features developed by Microsoft Research didn't make it to the SuperFetch version in Windows Vista, but the technology is improving, and is likely to be featured in future service packs.

For the technical folk reading this article Super Fetch is implemented in %SystemRoot%\System32\Sysmain.dll as a Windows service that runs inside a Service Host process (%SystemRoot%\System32\Svchost.exe).