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

[Rafael J. Wysocki]

On Monday, September 12, 2016 11:15:45 PM Rafael J. Wysocki wrote:
> On Monday, September 12, 2016 06:14:44 PM Peter Zijlstra wrote:
> > 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?
> 
> The performance governor doesn't do any IPIs.
> 
> At this point I'm not sure what's going on.

I've just tried and switching over to the performance governor makes
dbs_work_handler go away for me (w/ -rc4 with some extra irrelevant patches
on top) as it should.

What doesn't work, in particular?

Thanks,
Rafael