Messages in this thread | | | Date | Thu, 21 Apr 2016 09:09:43 +0800 | Subject | Re: [PATCH] sched/cpufreq: don't trigger cpufreq update w/o real rt/deadline tasks running | From | Wanpeng Li <> |
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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 [...]
Regards, Wanpeng Li
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