Inside Windows 8: Jon Berry - Desktop Activity Moderator and Connected Standby
- Posted: Jan 07, 2013 at 5:55AM
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Jon Berry, a veteran Windows engineer, digs into the new way Windows 8 manages processes to support the brave new world of Windows running on various CPU architectures including ARM and ATOM, which present an interesting set of technical challenges given the need to aggressively preserve energy when running—yet not fully running—while in a battery-powered state.
Jon owns the Desktop Activity Moderator (DAM), which, as the name implies, moderates desktop processes. The DAM is one of several new features in Windows 8 designed to ensure consistent, long battery life for devices that support connected standby.
Connected standby occurs when the device is powered on but the screen is turned off. In this power state, the system is technically always "on" (to support key scenarios like mail, VoIP, social networking, and instant messaging with Windows Store apps). It is analogous to the state a smart phone is in when the user presses the power button.
As such, software (including apps and operating system software) must be well-behaved during connected standby. The DAM was created to suppress desktop app execution in a manner similar to the Sleep state. It does this by suspending or throttling desktop software processes across the system upon connected standby entry. This enables systems that support connected standby to deliver minimized resource usage and long, consistent battery life while enabling Windows Store apps to deliver the connected experiences they promise.
The DAM is a kernel mode driver that is loaded and initialized at system boot if the system supports connected standby.
How does Windows 8 provide this always-on experience and not drain the battery in 10 minutes? What does the DAM actually do? How does it work? The DAM is part of a larger management system, which Jon also describes here. What is connected standby, exactly? Jon spends a lot of time at the whiteboard answering these and other questions. Thank you, Jon!
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