Microsoft aims to limit memory use in Windows 8

As it continues work on Windows 8, Microsoft is finding ways to limit memory use by its upcoming flagship operating system.

Windows performance team group program manager Bill Karagounis said memory use is a core issue for Windows 8, as better memory management can prolong battery life.

"Something that might not be obvious is that minimizing memory usage on low-power platforms can prolong battery life. Huh? In any PC, RAM is constantly consuming power. If an OS uses a lot of memory, it can force device manufacturers to include more physical RAM. The more RAM you have on board, the more power it uses, the less battery life you get," he said in a blog post.

He pointed out Windows 8 is being designed for SoC-based devices characterized by low power consumption.

This makes it even more important to leave lots of memory available for multiple concurrent apps and to sustain the overall responsiveness of devices, he said.

Karagounis noted having additional RAM on a tablet device can in some cases shave days off a single battery charge.

Memory usage goals

Karagounis said their goal with Windows 8 from the beginning was to ship with the same system requirements as Windows 7.

"We wanted to ensure that people running on Windows 7-era hardware would have the option to easily upgrade their existing machines to Windows 8 and take advantage of the functionality it has to offer. We also expect that many machines that predate the Windows 7 release will run Windows 8 based on the experiences we’ve had with older machines we intentionally keep in our performance test infrastructure," he said.

Making room for memory

Karagounis outlined some changes in Windows 8 to minimize memory use by the operating system. These include:

• Memory combining: Windows will attempt to free up duplicate or redundant copies of data across system RAM, which can liberate thousands of megabytes of memory.
  
• Service changes and reductions: Remove about 13 service, move a different set of services to “manual" start, and make some of the “always running" services move to a “start on demand" model.
  
  "Plug and Play, Windows Update, and the the user mode driver framework service are all trigger-started in Windows 8, in contrast to Windows 7, where these services were always running," Karagounis said.
  
• Doing the same job with less memory
  
• Lazy initialization of the “desktop": Windows 8 will only initialize OS components unique to the desktop environment when necessary. This is another source of memory savings, approximately 23MB right now.
  
• More granular prioritization of memory: Windows can make better decisions about what memory to keep around and what memory to remove sooner.

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