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    SubjectRe: Memory leak in 2.0.33 ??

    On Tue, 23 Dec 1997, Benjamin C.R. LaHaise wrote:
    > I wonder if he might be seeing another bug I came across in all recent
    > kernels - kswapd will not swap out any shared privately mapped pages.

    Uhhuh, that's a long-standing one that I'm nervous about changing. The
    problem is the "privately" part - if the page really is private then
    everything is ok, but a shared dirty page we cannot write out to multiple
    places because that would "unshare" it.

    You are probably right that the particular piece of code can only happen
    for private pages, but I'll really have to think long and hard on that

    > (1) will only be true for privately mapped pages. Let's say a big process
    > like inn does a fork(). Now you have a nice chunk of memory that will
    > never be swapped out until the region is unmapped. This behaviour is
    > normally masked by the fork() then exec() nature of most applications.

    Right. That will fix up any dirty COW pages. Can we absolutely guarantee
    that there are no dirty shared pages when we reach point (2)?

    > Linus: could you comment on this?

    I'd like to apply the patch, but I'd really like to be absolutely sure it
    cannot ever result in "disassociating" a page that really _is_ shared (not
    just COW) between two processes..


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