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Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue

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On Wed, Jan 13, 2016 at 05:01:31PM +0100, Frederic Weisbecker wrote:
> The full nohz CPU load is currently accounted on tick restart only.
> But there are a few issues with this model:
> 
> _ On tick restart, if cpu_load[0] doesn't contain the load of the actual
>   tickless load that just ran, we are going to account a wrong value.
>   And it is very likely to be so given that cpu_load[0] doesn't have
>   an opportunity to be updated between tick stop and tick restart.
> 
> _ If the runqueue had updates that didn't trigger a tick restart, we
>   are going to miss those CPU load changes.
> 
> A solution to fix this is to update the CPU load everytime we enqueue
> or dequeue a task in the fair runqueue and more than a jiffy occured
> since the last update.

Would not a much better solution be to do this remotely instead of from
one of the hottest functions in the scheduler?

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Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Peter Zijlstra <peterz@infradead.org> - 2016-01-19 14:20 +0100
  Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-19 18:10 +0100
    Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Peter Zijlstra <peterz@infradead.org> - 2016-01-20 10:20 +0100
      Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 16:00 +0100
        Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 16:20 +0100
          Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Christoph Lameter <cl@linux.com> - 2016-01-20 16:20 +0100
            Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 18:00 +0100
          Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 17:50 +0100
        Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Peter Zijlstra <peterz@infradead.org> - 2016-01-20 18:00 +0100
          Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 18:30 +0100
            Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Peter Zijlstra <peterz@infradead.org> - 2016-01-20 19:30 +0100
              Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-21 14:30 +0100

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