Re: Exe compression... and a nice tip.

From: Maarten Wiltink (maarten_at_kittensandcats.net)
Date: 02/22/05

  • Next message: Maarten Wiltink: "Re: speaking of the .Data" 
    Date: Tue, 22 Feb 2005 09:28:42 +0100

    "Raptor" <bogus@none.com> wrote in message
    news:cve3hh01onh@news2.newsguy.com...
    > Bruce Roberts <ber@bounceitattcanada.xnet> wrote in message
    > news:qToSd.2970$uO.220364@news20.bellglobal.com...

    >> But have you considered the real performance cost? When a compressed
    >> exe is used it is no longer possible to simply toss executable pages
    >> when swapping takes place. They actually have to be written to the
    >> swap file. Nor can code be shared by multiple instances.
    >
    > Are you saying that the EXE is not decompressed to look like the
    > native app in memory?

    No, it is, and he's not saying it isn't. But with an uncompressed
    executable, pages of loaded code are interchangeable with the disk
    image. So when memory gets short, code pages can be simply thrown
    away and reloaded when they're needed again, and the latter is a
    simpler operation than you might think. Also, when two instances are
    running, a single page of code can be mapped into both processes'
    address space, saving physical memory.

    A compressed executable is decompressed into a data segment. That data
    segment belongs to a single process and can't be shared. And when it's
    swapped out, it needs to be saved in the page file because it's not an
    exact copy of something on disk.

    So you're expending disk I/O to save disk space. Guess which one is
    the cheapest part of your computer, and which is the most expensive?

    Groetjes,
    Maarten Wiltink

  • Next message: Maarten Wiltink: "Re: speaking of the .Data"

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