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    SubjectRe: ~500 megs cached yet 2.6.5 goes into swap hell
    Andrew Morton wrote:
    > Paul Mackerras <paulus@samba.org> wrote:
    >
    >>Andrew Morton writes:
    >>
    >>
    >>>My point is that decreasing the tendency of the kernel to swap stuff out is
    >>>wrong. You really don't want hundreds of megabytes of BloatyApp's
    >>>untouched memory floating about in the machine. Get it out on the disk,
    >>>use the memory for something useful.
    >>
    >>What I have noticed with 2.6.6-rc1 on my dual G5 is that if I rsync a
    >>gigabyte or so of data over to another machine, it then takes several
    >>seconds to change focus from one window to another. I can see it
    >>slowly redraw the window title bars. It looks like the window manager
    >>is getting swapped/paged out.
    >>
    >>This machine has 2.5GB of ram, so I really don't see why it would need
    >>to swap at all. There should be plenty of page cache pages that are
    >>clean and not in use by any process that could be discarded. It seems
    >>like as soon as there is any memory shortage at all it picks on the
    >>window manager and chucks out all its pages. :(
    >>
    >
    >
    > I suspect rsync is taking two passes across the source files for its
    > checksumming thing. If so, this will defeat the pagecache use-once logic.
    > The kernel sees the second touch of the pages and assumes that there will
    > be a third touch.
    >

    I'm not very impressed with the pagecache use-once logic, and I
    have a patch to remove it completely and treat non-mapped touches
    (IMO) more sanely.
    -
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