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    SubjectRe: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option
    On Thu, Jul 27, 2017 at 10:53:12AM +0200, Peter Zijlstra wrote:
    > On Wed, Jul 26, 2017 at 06:01:15PM +0000, Mathieu Desnoyers wrote:
    >
    > > Another alternative for a MEMBARRIER_CMD_SHARED_EXPEDITED would be rate-limiting
    > > per thread. For instance, we could add a new "ulimit" that would bound the
    > > number of expedited membarrier per thread that can be done per millisecond,
    > > and switch to synchronize_sched() whenever a thread goes beyond that limit
    > > for the rest of the time-slot.
    >
    > You forgot to ask yourself how you could abuse this.. just spawn more
    > threads.
    >
    > Per-thread limits are nearly useless, because spawning new threads is
    > cheap.

    Agreed -- any per-thread limit has to be some portion/fraction of a
    global limit.

    Thanx, Paul

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