High Page outs:Pages ins ratio, but a lot of free memory

Discussion in 'MacBook Pro' started by PJM, May 19, 2009.

  1. PJM macrumors newbie

    Joined:
    Oct 16, 2007
    #1
    Today I have seen the beach ball on my laptop several times. I checked the Activity Monitor and noticed the page outs/pages ins ratio is too high (around 80%). Usually, that means “buy more RAM”. However, my MBP has 4GB and I am using less than 1GB. How is that possible? What wrong?
     
  2. pj- macrumors member

    Joined:
    Oct 31, 2008
    #2
    I've had my mbp with 4gb of ram since october and I've never seen the page out counter go above 0.

    I just loaded a crap load apps to up my ram usage, and even with 3.5gb of ram used, including an instance of Windows 7 on VMWare fusion, it's holding steady at 27 page outs (570,000 page ins);

    I'd start turning off apps one by one until it drops.
     
  3. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #3
    You get page in and out when the computer needs more RAM than you have; when it doesn't, you'll have free RAM; it's when you constantly don't have free RAM and you have a lot of page ins and outs, that you need to buy more RAM.
     
  4. ppc750fx macrumors 65816

    Joined:
    Aug 20, 2008
    #4
    OS X's VM implementation is really quite aggressive when it comes to paging. I wouldn't worry about it too much -- if you start running into major performance problems or if you experience thrashing then you can start worrying, but other than that I wouldn't be too concerned.
     
  5. pesc macrumors regular

    Joined:
    Jan 20, 2006
    #5
    It is possible to write applications that don't read/write files through normal read/write calls, but instead map the files directly into memory and use the OS X virtual memory manager for file access. If you run such applications, you will get page in / out whenever the program wants to read or write to the file.

    Having this in mind, it is very difficult to give any recommendations on what ratio there should be between page in/out, or if "excessive" paging necessarily means that you have run out of memory.
     
  6. philips macrumors regular

    philips

    Joined:
    Oct 14, 2004
    Location:
    Baden-Württemberg, Germany
    #6
    +1. I confirm that as *nix developer.

    Also note that Mac OS X, as inherited from traditional BSD, has quite strict caching. That is a compromise to make sure that data would be written to disk sooner than later.

    I would try to observe in Activity Monitor processes which have highest CPU usage and stop them one by one to identify which one is guilty.

    P.S. I have checked Mac OS X's *nix tools, I do not see anything what can help. Theoretically, "ps -eao pid,comm,minflt,majflt,inblock,oublock,nswap" should have identified the offending processes, yet the last five rows are "-" instead of numbers (at least on my system). No fancy Solaris (mpstat) or Linux (pidstat) tools seem to be available.
     

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