The Lifer

OS X Mavericks is generating a lot of buzz with its stick-looking app upgrades, but Rik Myslewski is more excited about the features we can’t see

Apple’s OS X Mavericks adds a number of nifty features — I’m particularly jazzed about improvements to the Finder, Safari, and the Calendar app — but even more interesting to us in the geek community are a trio of under-the-hood items that boost both performance and battery life.

The first goes by the oh-so-cute name of App Nap — definitely a «What took you so long?» feature. App Nap keeps an eye on the apps you’re using and the pages you’re viewing in Safari, and when one of them is hidden behind a window or in another tab, it puts that app or page into a low-power state, thus saving precious battery juice.

If you don’t think this is a big deal, hie yourself over to Applications/Utilities and fire up Activity Monitor. Then launch the exceptionally cool in Safari, select the «% CPU» column in Activity Monitor, and check out what pops to the top of that list. Now open another Safari tab, and notice that the wind map is still chewing up power, even though you’re not viewing it. App Nap is intended to prevent this inefficiency.

But don’t worry about such tasks as a power-hungry video-encoding project slipping into a low-power state when you move into another window. Thankfully, developers can tell App Nap not to chill their apps — thoughtful of Apple, eh?

Another bit of Maverickian niftiness is Compressed Memory, which frees up RAM room by, uh, compressing memory. Let me explain: your Mac has only so much memory. (Mavericks can support up to 128GB, but can you afford that much? I can’t.) As a result, applications often need to take some of the data they’re working on and swap it out to your Mac’s oh-so-much-slower storage device — its hard drive or SSD, that is — in a scheme called «virtual memory,» which bogs everything down and may require power to wake up the storage device.

To the rescue comes a clever little thing called the WKdm (Wilson-Kaplan direct mapped) compression algorithm. This bit of code keeps an eye on RAM contents that haven’t recently been used, and swiftly compresses them down to about half their original size, thus both freeing RAM space and lessening the need for virtual memory. What’s more, when an app needs data from that compressed memory, all your Mac’s cores can whip it instantly back into shape, unlike retrieving data from storage, which is a one-core-only task. Paul Wilson and Scott Kaplan came up with WKdm way back in 1997, by the way, so you can file this improvement under «WTYSL?» as well.

Our final welcome latecomer is Timer Coalescing, which PC folks have enjoyed since Windows 7 released in late 2009. This one’s a wee bit harder to explain, but bear with me and you can be the Bull Geek at the next gathering of your local technorati.

Your apps, operating system, Wi-Fi signals, and other processes constantly send tiny li’l messages called «timers» to your Mac to check in and find out whether anything has changed that they need to take care of. When your Mac is plugged into the wall, no problem; but when it’s running on battery power, this shower of timers keeps waking up your CPU from its preferred power-saving state. Timer Coalescing groups that random shower into bundles of timers that arrive at the CPU together, thus allowing it to take longer naps between wake-up calls — and to the Intel Core Processor in your Mac, even 50 to 100 milliseconds is long enough for a refreshing snoozefest.

Speaking of CPUs, Intel’s latest-and-greatest 4th-generation line, code-named «Haswell,» also has a host of improvements that enhance both performance and battery life. It’s a good time to be a Mac user.

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