Windows 8 to reduce memory usage

Microsoft has tweaked the use of memory in Windows 8 to help people juggle more applications and files with less physical RAM.

In the latest Building Windows 8 blog, Bill Karagounis, group program manager for Microsoft's Performance team, detailed some of the tricks that the company has employed in the new OS to optimize the use of memory.

One such trick is memory combining. Windows applications can reserve multiple chunks of system memory, not just what for they need now but what for they may need in the future. The more apps that do this, the more memory used up.

Memory combining searches system RAM for duplicate content and then frees up the duplicates to hold just a single copy. If an app needs that freed-up memory in the future, Windows provides what's called a "private copy." Such a process can make anywhere from 10s to 100s of megabytes available, according to Karagounis.

A healthy amount of system RAM is also taken up by Windows services. Open Task Manager, click on the Services tab, and you'll see the sheer number of services chewing up precious memory. To make Windows 8 more memory efficient, Microsoft has removed 13 different services, changed a number of others from automatic to manual, and moved still others into a "Start on Demand" mode so they're not eating up memory from the get-go.

Yet another trick was to find various core but low-level components that have been in Windows for almost 20 years and consolidate certain ones so they don't take up as heavy a memory footprint as they would individually.

Finally, Windows 8 will be smarter about which allocated memory to keep and which to free up. For example, antivirus programs need memory when they check on files opened by other applications. Since this is typically a one-time allocation, that specific chunk of memory probably wouldn't be needed again by the AV software. As such, Windows 7 might free up that RAM for something else if memory became scare. But such an action could drag down performance.

Instead, "In Windows 8, any program has the ability to allocate memory as 'low priority,' Karagounis said. "This is an important signal to Windows that if there is memory pressure, Windows can remove this low priority memory to make space, and it doesn't affect other memory required to sustain the responsiveness of the system."

Overall, the new memory optimization should coax better performance out of PCs with an ample supply of RAM but also benefit those with only 1 or 2 gigabytes of memory. As an example, Karagounis looked at the Netbook that Windows president Steven Sinofsky used in a demo at the company's recent Build conference. Comparing the PC's memory usage under Windows 7 and Windows 8 under the same conditions, Karagounis found that Windows 7 chewed up 404MB of RAM, while Windows 8 used only 281MB.

The tweaks will also squeeze more juice out of tablets and other lower-powered devices that don't hold much physical RAM, explained Karagounis. The more RAM a device contains, the more battery power it chews up. Manufacturers of Windows 8 devices can now get by with less physical memory, thereby delivering more life on a single battery charge.