Messages in this thread | | | Date | Thu, 27 Jul 2017 06:14:18 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option |
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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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