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    SubjectRe: [PATCH] include private data mappings in RLIMIT_DATA limit
    On Tue, 10 Jul 2007, Dave McCracken wrote:
    > On Tuesday 10 July 2007, Hugh Dickins wrote:
    > >
    > > Mapped private readonly yes, but vm_stat_account() says
    > > if (file) {
    > > mm->shared_vm += pages;
    > > if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
    > > mm->exec_vm += pages;
    >
    > In that code shared_vm includes everything that's mmap()ed, including private
    > mappings. But if you look at Herbert's patch he has the following change:
    >
    > if (file) {
    > - mm->shared_vm += pages;
    > + if (flags & VM_SHARED)
    > + mm->shared_vm += pages;
    > if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
    > mm->exec_vm += pages;
    >
    > This means that shared_vm now is truly only memory that's mapped VM_SHARED and
    > does not include VM_EXEC memory. That necessitates the separate subtraction
    > of exec_vm in the data calculations.

    Ah, I just noticed at the beginning of the patch, and didn't look for
    a balancing change - thanks. I'd strongly recommend that he not mess
    around with these numbers, unless there's _very_ good reason: they're
    not ideal, nothing ever will be, changing them around just causes pain.
    shared_vm may not be a full description of what it counts, but it'll
    do until you've a better name (readonly mappings share with the file
    even when they're private).

    Hugh
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