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    SubjectRe: Rationale for RLIMIT_MEMLOCK?

    > > > 4. Is the default hard limit of 32 kB initialized by the kernel or
    > >
    > > the kernel has a relatively low default. The reason is simple: allow too
    > > much mlock and the user can DoS the machine too easy. The kernel default
    > > should be safe, the admin / distro can very easily override anyway.
    > This doesn't appear to happen for SUSE 10.0, which causes trouble with
    > some of the "multimedia apps" BTW... apparently the limit was lowered at
    > the same time as the root restrictions were relaxed.

    yes the behavior is like this

    root non-root
    before about half of ram nothing
    after all of ram by default small, increasable

    > Such changes in behavior aren't adequate for 2.6.X, there are way too
    > many applications that can't be bothered to check the patchlevel of the
    > kernel, and it's totally unintuitive to users, too.

    there is NO fundamental change here other than a *general* relaxing.
    This is important to note: Apps that could mlock before STILL can mlock.
    Only apps that would depend on mlock failing with a security check, and
    only those who do small portions, break now because suddenly the mlock
    succeeds. Big deal... those would have broken when run as root already

    > No, I'm not doing that. I rather wonder why it's so low, or whom a certain
    > percentage such as RAM >> 5 (that's 3.125 %) would hurt. A

    because it's generally a PER PROCESS limit, so fork 60 times and kaboom
    things explode. (You can argue you can forkbomb anyway, but that's
    where the process count rlimit comes in)

    > Allowing
    > unlimited memory allocation while at the same time allowing only 32 kB
    > of mlock()ed memory seems disproportionate to me.

    it's not. Normal memory is swapable. And thus a far less rare commodity
    than precious pinned down memory.

    What application do you have in mind that broke by this relaxing of

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      Last update: 2006-01-23 18:02    [W:2.430 / U:2.080 seconds]
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