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    SubjectRe: the new VMt
    Hi,

    On Mon, Sep 25, 2000 at 03:12:50PM -0600, yodaiken@fsmlabs.com wrote:
    > > >
    > > > I'm not too sure of what you have in mind, but if it is
    > > > "process creates vast virtual space to generate many page table
    > > > entries -- using mmap"
    > > > the answer is, virtual address space quotas and mmap should kill
    > > > the process on low mem for page tables.
    > >
    > > No. Page tables are not freed after munmap (and for good reason). The
    > > counting of page table "beans" is critical.
    >
    > I've seen the assertion before, reasons would be interesting.

    Reason 1: under DoS attack, you want to target not the process using
    the most resources, but the *user* using the most resources (else a
    fork-bomb style attack can work around your OOM-killer algorithms).

    Reason 2: if you've got tasks stuck in low-level page allocation
    routines, then you can't immediately kill -9 them, so reactive OOM
    killing always has vulnerabilities --- to be robust in preventing
    resource exhaustion you want limits on the use of those resources
    before they are exhausted --- the necessary accounting being part of
    what we refer to as "beancounter".

    --Stephen
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