Re: Ping: [PATCH v15 00/13] support "task_isolation" mode

[Peter Zijlstra]

On Mon, Sep 12, 2016 at 12:01:58PM -0400, Chris Metcalf wrote:
> On 9/7/2016 5:11 PM, Francis Giraldeau wrote:
> >When running only the test_jitter(), the isolation mode is lost:
> >
> >     [ 6741.566048] isolation/9515: task_isolation mode lost due to irq_work
> >
> >With ftrace (events/workqueue/workqueue_execute_start), I get a bit more info:
> >
> >      kworker/1:1-676   [001] ....  6610.097128: workqueue_execute_start: work struct ffff8801a784ca20: function dbs_work_handler
> >
> >The governor was ondemand, so I tried to set the frequency scaling
> >governor to performance, but that does not solve the issue. Is there
> >a way to suppress this irq_work? Should we run the isolated task with
> >high real-time priority, such that it never get preempted?
> 
> On the tile platform we don't have the frequency scaling stuff to contend with, so
> I don't know much about it.  I'd be very curious to know what you can figure out
> on this front.

Rafael, I'm thinking the performance governor should be able to run
without sending IPIs. Is there anything we can quickly do about that?