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

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue
Date	2016-01-20 10:10 +0100
Message-ID	<qSWW6-4hT-15@gated-at.bofh.it> (permalink)
References	<qQw9J-2at-33@gated-at.bofh.it> <qQw9J-2at-41@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, 13 Jan 2016, Frederic Weisbecker wrote:
> 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.

That's not a solution. That's just crap.

I tell you since years, that you need to fix that remote accounting stuff,
but no, you insist on adding more trainwrecks left and right.

> The problem with doing this remotely is that we can miss past cpu loads if
> there was several enqueue/dequeue operations happening while tickless.

That's complete bullshit.

1) How is remote accounting that happens every tick different from local
   accounting which happens every tick?

2) How do you have enqueue/dequeue operations when you are running in full
   nohz, i.e. one task is consuming 100% cpu time in user space?

I'm really tired of that tinkering. The proper solution is to make NOHZ_FULL
depend on BROKEN.

Thanks,

	tglx

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Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 10:10 +0100
  Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 15:40 +0100
    Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 15:50 +0100
      Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task  enqueue/dequeue Christoph Lameter <cl@linux.com> - 2016-01-20 17:50 +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 Frederic Weisbecker <fweisbec@gmail.com> - 2016-01-20 17:50 +0100

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