Messages in this thread | | | Date | Tue, 1 Aug 2017 16:32:03 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [RFC PATCH v2] membarrier: expedited private command |
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On Tue, Aug 01, 2017 at 04:16:54PM +0200, Peter Zijlstra wrote: > On Tue, Aug 01, 2017 at 06:23:09AM -0700, Paul E. McKenney wrote: > > On Tue, Aug 01, 2017 at 12:22:03PM +0200, Peter Zijlstra wrote: > > > > [ . . . ] > > > > > As to scheduler IPIs, those are limited to the CPUs the user is limited > > > to and are rate limited by the wakeup-latency of the tasks. After all, > > > all the time a task is runnable but not running, wakeups are no-ops. > > > > Can't that wakeup-latency limitation be overcome by a normal user simply > > by having lots of tasks to wake up, which then go back to sleep almost > > immediately? Coupled with very a low-priority CPU-bound task on each CPU? > > Let me put it like this; there is no way to cause more interference > using IPIs then there is simply running while(1) loops ;-)
Very good, that does give us some guidance, give or take context switches happening during the IPI latency window. ;-)
Thanx, Paul
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