Messages in this thread | | | Date | Sat, 23 Jun 2018 11:47:55 -0700 | From | Fenghua Yu <> | Subject | Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses |
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On Fri, Jun 22, 2018 at 12:13:37AM +0200, Peter Zijlstra wrote: > On Thu, Jun 21, 2018 at 03:00:03PM -0700, Fenghua Yu wrote: > > For example, on a consolidated real-time machine, some cores are running > > > Another example, in a public cloud deployed in the field, a user process > > In either case a single split-lock shouldn't be a real problem, if you > program the event with a count of 1 and have the NMI handler kill the > offending task, you should be good. > > Not saying the #AC isn't nicer, just saying the PMU based thing can > still work.
The difference between perf event and #AC for split lock is perf event is after the fact while #AC is before the fact.
In the examples (esp. the first example), hard real time cannot afforrd a split lock/bus lock. Perf captures the event and kill the task; but the split lock has been issued and harm has been done. #AC for split lock kills the task before the task generates split lock or bus lock to hurt real time tasks.
Thanks.
-Fenghua
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