Compressed Memory alone makes Apple’s OS Mavericks a valuable upgrade

“A new feature of Mac OS 10.9 – Mavericks – compressed memory, increases the effective size of DRAM through inline data compression,” Robin Harris reports for ZDNet. “This isn’t a new idea: over 20 years ago the HP Omnibook 300 used inline compression to double the effective size of its 10MB compact flash card.”

“What is new is that with multiple cores running an optimized compression algorithm the system can compress/decompress data much faster than swapping to disk or SSD. This saves time and energy, since the system isn’t idling waiting for memory page swaps – important for notebooks,” Harris reports. “And there’s nothing to configure: it works automatically in the background. All you see is a more stable Mac with more memory.”

“With Mavericks memory compression I’m seeing much improved behavior from my MacBook Air: tiny swap file sizes; greater stability; and no performance hit. Even with Safari open for almost 4 days and dozens of open tabs, Final Cut Pro, Preview, Mail, VLC, an FTP client, text editor and the usual dozens of background tasks the swap file is a tiny 114MB where normally it would be at least 2500MB – hurting performance – and growing fast,” Harris reports. “If you were skeptical about the value of a free OS update, fret no more: this single feature makes a lightweight notebook much more viable for power users.”

Read more in the full article here.

Related articles:
Five key features of Apple’s new OS X Mavericks – October 28, 2013
How to improve Mac performance: OS X 10.9 Mavericks edition – October 25, 2013
Ars Technica reviews Apple’s OS X 10.9 Mavericks: A no-brainer upgrade – October 25, 2013
TechCrunch reviews Apple’s OS X Mavericks: Update your Mac as soon as you can – October 24, 2013
Like wildfire: OS X Mavericks adoption passes 7% in less than 24 hours – October 23, 2013
Free OS X Mavericks will pay off for Apple in many ways – October 23, 2013
PC Magazine reviews Apple’s OS X 10.9 Mavericks: ‘Apple got it right’ – Editors’ Choice – October 23, 2013
Been awful knowin’ ya, Microsoft: Revolutionary Apple ends the era of paid operating systems, office suites – October 23, 2013
Apple makes the world’s most advanced operating system freeware – October 23, 2013
Apple’s new free OS X for Mac hurts Microsoft and the Windows PC industry in myriad ways – October 22, 2013
Apple exploits Microsoft’s confused hesitation on Office for iPad – October 22, 2013
Apple’s OS X Mavericks available today free from the Mac App Store – October 22, 2013
Apple releases next-gen 64-bit iWork and iLife apps for OS X and iOS; free with new Macs and iOS devices – October 22, 2013


  1. Before “page outs” indicated if you needed more RAM.
    What do you look at now to determine if you need more RAM? “Swap Used”???

    Also prior to Mavericks “page outs” was relative to “page ins”.

    Bottom line… compressed memory sounds great, but how do you know if you need more RAM in Mavericks Activity Monitor?

      1. With Compressed Memory and App Nap, it feels like there is no longer a real reason to quit open apps on my MacBook Pro. As far as I can tell, quitting apps has no effect on performance. All it seems to do anymore is waste the brief amount of time it takes me to think about it and hit ⌘ Q.

        I still quit open apps out of habit, but don’t intend to continue.

        1. An app that is napping is not given CPU cycles, but conserves its memory footprint. However, the automatic termination feature will close it if needed, thus reclaiming the used memory.

    1. Open Activity Monitor. Click on the Memory tab then look at the bottom panel. The Memory Pressure graphic tells you if your system could benefit from more RAM.

      Simple, elegant, and accurate. So Apple-y.

    2. I found the answer to my question, so I’d like to share it.

      To know if you need more RAM under Mavericks go about your daily activities
      under Activity Monitor -> Memory
      look at the 2 bottom numbers
      Swap Used:

      First info that wants to stay in RAM but you do not have enough physical RAM will become compressed and the value under Compressed will increase. Once memory compression is STILL not enough the data gets swapped to the hard drive and then the value under Swap Used: will increase.

      I ideally both values Compressed: Swap Used: will remain ZERO if you have enough RAM

      The Memory Pressure graph is graphical representation (vs. numerical) of the same thing.

      1. Cheers Bill! Hadn’t seen the memory pressure thing before. On the MBA with 4 GB physical, I turned on iTunes, Aperture (35,000 originals library), Safari, and iMovie, iBooks, then opened VMWare/Win7/Chrome+Word and the pressure still less than 80% and no virtual being used until Windows Chrome started. Interesting having shut VMWare, it’s now got 5 GB virtual available and pressure down to 40%. Not sure what it all means but I think, yes, it like the old RAM Doubler or Mac virtual of OS8 and 9 days. {Yea, it was kludgy but people have forgotten (extension clashes aside) how excellent and enjoyable OS9 was as a user experience.}

  2. RAM Doubler (Used on my Apple IIc & IIGs.
    What I want to know is why Mac OS (and others) have so much virtual RAM in use when my real much faster RAM is left empty.
    I mean I have 16GB of physical RAM and and when I look the system is using 6GB and the rest is in VRAM.

  3. BS!

    My 32 GB MacPro is “running out of application memory” because Mail is taking 15 GB alone!
    And, WTF is “Memory Pressure”? Wired, Active, Free & Inactive readings are gone. Now we have a dumbed-down “Memory pressure”!

    Both Apple Support and Engineering has been in touch, gotten tar balls, spin dumps and I am awaiting the day that I can again read email on my machine.

    Hair Force One, screw compressed memory — give me back a stable system!

    1. Strange. Mavericks on my 2012 i7 Mac Mini with only 4GB of memory seems to be very efficient and leaving me with around 1.5GB of free memory during most of the things I use it for. Maybe it depends on what applications are being run. Even when I’m running VMWare Fusion 5 I’m left with about 800MB of free memory to spare. No beach-balls or hesitation that I’ve noticed. The Mac Mini doesn’t seem to be struggling with anything I use it for. Maybe if you run Onyx or some other system utility you might be able to fix some of those problems you’re having.

    2. Had similar problem– RAM usage ballooned to 2 GB (out of 4), slow as heck, etc.

      Backed up the Mail preferences and rebuilt it from zero and it runs fine now.

      Obviously a corrupt preference file since I literally removed all accounts before I gave up and rebuilt, but I didn’t try finding out which ones.

        1. In Finder, go to menu Go > Go to Folder… (or cmd-shift G), and type in “~/Library” (without the quotes). I think starting with Lion, Apple hid this folder.

          In the Library folder is the Mail folder, which includes all the account, mailbox and configuration data. Either duplicate the folder where it is or copy it to backup location.

  4. Mavericks has made my early 2008 MBP pretty useless with 2 GB. I’ve ordered a 4 GB set in hopes it can recover.

    Claims to the value of Mavericks for others really apply opposite to my machine. It is presently 1/3 as fast as before after a few days and several reboots.

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