RE: [SLE] swap space question in 9.3 install

From: Greg Wallace (jgregw_at_acsalaska.net)
Date: 07/29/05

  • Next message: Jerry Feldman: "Re: [SLE] swap space question in 9.3 install" 
    To: <suse-linux-e@suse.com>
Date: Fri, 29 Jul 2005 06:05:23 -0800

    On Friday, July 29, 2005 @ 5:32 AM, Randall Schulz wrote:

    >Hi,

    >On Thursday 28 July 2005 21:44, Greg Wallace wrote:
    >> ...
    >>
    >> Interesting. On a Windoze machine, when you start a program, it
    >> loads two copies of the program into memory, one into cache and one
    >> into active memory. If you close the program, the active memory area
    >> is freed, but the cached copy stays there until you do a restart or
    >> until the memory runs low and Windoze needs to reuse it. If you turn
    >> right around and re-start the program, the program is copied from the
    >> cache area of RAM over to the active memory area (a memory to memory
    >> copy), so that it starts faster the second time. Is this the same
    >> thing with swap on Linux? Is everything in "used" also in "cached",
    >> along with some copies of programs that are no longer executing (I
    >> e., the memory is available for re-use, if necessary, but also
    >> available for a fast load of the program)?

    >For the way most programs are linked, the text (and some of the
    >pre-initialized data) is considered "pure" (read-only) and thus
    >shareable. Furthermore the linker can align the pure code and data
    >within the object file so it's properly aligned to the hardware's
    >paging boundaries. Then the OS need never copy that information to swap
    >space. Demand paging retrieves it directly from the executable program
    >or shared-object file. When a page holding pure code or data is to be
    >replace, it's simply abandoned, never needing to be paged out.

    >> Greg Wallace

    >Randall Schulz

    So are you saying that this "pure" code is still re-read from disk, or can
    it be sometimes available for use directly from a previously loaded "pure"
    copy in RAM? I. e., is a RAM copy ever available for re-use after a program
    has finished, or is it always re-loaded from disk (whether from swap or from
    the file copy itself)?

    Greg Wallace 

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  • Next message: Jerry Feldman: "Re: [SLE] swap space question in 9.3 install"

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