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    SubjectRe: [PATCH] ipc,shm: disable shmmax and shmall by default
    Hi Davidlohr,

    On 04/03/2014 02:20 AM, Davidlohr Bueso wrote:
    > The default size for shmmax is, and always has been, 32Mb.
    > Today, in the XXI century, it seems that this value is rather small,
    > making users have to increase it via sysctl, which can cause
    > unnecessary work and userspace application workarounds[1].
    >
    > Instead of choosing yet another arbitrary value, larger than 32Mb,
    > this patch disables the use of both shmmax and shmall by default,
    > allowing users to create segments of unlimited sizes. Users and
    > applications that already explicitly set these values through sysctl
    > are left untouched, and thus does not change any of the behavior.
    >
    > So a value of 0 bytes or pages, for shmmax and shmall, respectively,
    > implies unlimited memory, as opposed to disabling sysv shared memory.
    > This is safe as 0 cannot possibly be used previously as SHMMIN is
    > hardcoded to 1 and cannot be modified.
    Are we sure that no user space apps uses shmctl(IPC_INFO) and prints a
    pretty error message if shmall is too small?
    We would break these apps.

    --
    Manfred


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