On 2016-09-12 08:05 PM, Rafael J. Wysocki wrote: > 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. >>> >>> 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. Ho gosh, the command "cpufreq-set -g performance" sets the governor only for cpu0. I was expecting it to set for all cpus. The isolation test runs on cpu1 and this cpu was still with ondemand governor. With performance governor, the dbs_work_handler does not occurs anymore and the isolated task is not preempted by that kworker thread anymore. Sorry for the noise and thanks for checking! Francis -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
