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Groups > linux.kernel > #1313369
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue |
| Date | 2016-01-20 18:00 +0100 |
| Message-ID | <qT4gW-PQ-9@gated-at.bofh.it> (permalink) |
| References | (1 earlier) <qQw9J-2at-41@gated-at.bofh.it> <qSEmt-8o1-1@gated-at.bofh.it> <qSHX4-2s1-19@gated-at.bofh.it> <qSX5M-4m2-25@gated-at.bofh.it> <qT2oO-7Xe-21@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, Jan 20, 2016 at 03:54:19PM +0100, Frederic Weisbecker wrote:
> > You can simply do:
> >
> > for_each_nohzfull_cpu(cpu) {
> > struct rq *rq = rq_of(cpu);
> >
> > raw_spin_lock(&rq->lock);
> > update_cpu_load_active(rq);
> > raw_spin_unlock(&rq->lock);
> > }
>
> But from where should we do that?
house keeper thingy
> Maybe we can do it before we call source/target_load(), on the
> selected targets needed by the caller? The problem is that if we do
> that right after a task got enqueued on the nohz runqueue, we may
> accidentally account it as the whole dynticks frame (I mean, if we get
> rid of that enqueue/dequeue accounting).
Yes so? What if the current tick happens right after a task get
enqueued? Then we account the whole tick as !idle, even tough we might
have been idle for 99% of the time.
Not a problem, this is sampling.
Doing it locally or remotely doesn't matter.
> > Also, since when can we have enqueues/dequeues while NOHZ_FULL ? I
> > thought that was the 1 task 100% cpu case, there are no
> > enqueues/dequeues there.
>
> That's the most optimized case but we can definetly have small moments
> with more than one task running. For example if we have a workqueue,
> or such short and quick tasks.
The moment you have nr_running>1 the tick comes back on.
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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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