Messages in this thread | | | Subject | Re: [PATCH] sched/cpufreq: don't trigger cpufreq update w/o real rt/deadline tasks running | From | "Rafael J. Wysocki" <> | Date | Thu, 21 Apr 2016 13:11:50 +0200 |
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On 4/21/2016 3:09 AM, Wanpeng Li wrote: > 2016-04-21 6:28 GMT+08:00 Rafael J. Wysocki <rafael.j.wysocki@intel.com>: >> On 4/21/2016 12:24 AM, Wanpeng Li wrote: >>> 2016-04-20 22:01 GMT+08:00 Peter Zijlstra <peterz@infradead.org>: >>>> On Wed, Apr 20, 2016 at 02:32:35AM +0200, Rafael J. Wysocki wrote: >>>>> On Monday, April 18, 2016 01:51:24 PM Wanpeng Li wrote: >>>>>> Sometimes update_curr() is called w/o tasks actually running, it is >>>>>> captured by: >>>>>> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; >>>>>> We should not trigger cpufreq update in this case for rt/deadline >>>>>> classes, and this patch fix it. >>>>>> >>>>>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> >>>>> The signed-off-by tag should agree with the From: header. One way to >>>>> achieve >>>>> that is to add an extra From: line at the start of the changelog. >>>>> >>>>> That said, this looks like a good catch that should go into 4.6 to me. >>>>> >>>>> Peter, what do you think? >>>> I'm confused by the Changelog. *what* ? >>> Sometimes .update_curr hook is called w/o tasks actually running, it is >>> captured by: >>> >>> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; >>> >>> We should not trigger cpufreq update in this case for rt/deadline >>> classes, and this patch fix it. >> >> That's what you wrote in the changelog, no need to repeat that. >> >> I guess Peter is asking for more details, though. I actually would like to >> get some more details here too. Like an example of when the situation in >> question actually happens. > I add a print to print when delta_exec is zero for rt class, something > like below: > > watchdog/5-48 [005] d... 568.449095: update_curr_rt: rt > delta_exec is zero > watchdog/5-48 [005] d... 568.449104: <stack trace> > => pick_next_task_rt > => __schedule > => schedule > => smpboot_thread_fn > => kthread > => ret_from_fork > watchdog/5-48 [005] d... 568.449105: update_curr_rt: rt > delta_exec is zero > watchdog/5-48 [005] d... 568.449111: <stack trace> > => put_prev_task_rt > => pick_next_task_idle > => __schedule > => schedule > => smpboot_thread_fn > => kthread > => ret_from_fork > watchdog/6-56 [006] d... 568.510094: update_curr_rt: rt > delta_exec is zero > watchdog/6-56 [006] d... 568.510103: <stack trace> > => pick_next_task_rt > => __schedule > => schedule > => smpboot_thread_fn > => kthread > => ret_from_fork > watchdog/6-56 [006] d... 568.510105: update_curr_rt: rt > delta_exec is zero > watchdog/6-56 [006] d... 568.510111: <stack trace> > => put_prev_task_rt > => pick_next_task_idle > => __schedule > => schedule > => smpboot_thread_fn > => kthread > => ret_from_fork > [...]
And the statement in your changelog follows from this I suppose. How does it follow, exactly?
Thanks, Rafael
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