On Mon, Sep 12, 2016 at 12:01:58PM -0400, Chris Metcalf wrote:

On 9/7/2016 5:11 PM, Francis Giraldeau wrote:

quoted

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?