From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Byungchul Park <byungchul.park@lge.com>,
Chris Metcalf <cmetcalf@ezchip.com>,
Thomas Gleixner <tglx@linutronix.de>,
Luiz Capitulino <lcapitulino@redhat.com>,
Christoph Lameter <cl@linux.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Mike Galbraith <efault@gmx.de>, Rik van Riel <riel@redhat.com>
Subject: Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue
Date: Tue, 19 Jan 2016 14:17:08 +0100 [thread overview]
Message-ID: <20160119131708.GF6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1452700891-21807-5-git-send-email-fweisbec@gmail.com>
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?
next prev parent reply other threads:[~2016-01-19 13:17 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-13 16:01 [RFC PATCH 0/4] sched: Improve cpu load accounting with nohz Frederic Weisbecker
2016-01-13 16:01 ` [PATCH 1/4] sched: Don't account tickless CPU load on tick Frederic Weisbecker
2016-01-19 13:08 ` Peter Zijlstra
2016-01-19 16:22 ` Frederic Weisbecker
2016-01-19 18:56 ` Peter Zijlstra
2016-01-19 22:33 ` Frederic Weisbecker
2016-01-20 5:43 ` Byungchul Park
2016-01-20 10:26 ` Byungchul Park
2016-01-28 16:01 ` Frederic Weisbecker
2016-01-29 9:50 ` Peter Zijlstra
2016-02-01 10:05 ` Byungchul Park
2016-02-01 10:09 ` [PATCH] sched: calculate sched_clock_cpu without tick handling during nohz Byungchul Park
2016-02-01 10:34 ` [PATCH 1/4] sched: Don't account tickless CPU load on tick Peter Zijlstra
2016-02-01 23:51 ` Byungchul Park
2016-02-02 0:50 ` Byungchul Park
2016-02-01 6:33 ` Byungchul Park
2016-01-20 8:42 ` Thomas Gleixner
2016-01-20 17:36 ` Frederic Weisbecker
2016-01-22 8:40 ` Byungchul Park
2016-01-13 16:01 ` [PATCH 2/4] sched: Consolidate nohz CPU load update code Frederic Weisbecker
2016-01-14 2:30 ` Byungchul Park
2016-01-19 13:13 ` Peter Zijlstra
2016-01-20 0:51 ` Byungchul Park
2016-01-14 5:18 ` Byungchul Park
2016-01-19 13:13 ` Peter Zijlstra
2016-01-19 16:49 ` Frederic Weisbecker
2016-01-20 1:41 ` Byungchul Park
2016-02-29 11:14 ` [tip:sched/core] sched/fair: " tip-bot for Frederic Weisbecker
2016-01-13 16:01 ` [RFC PATCH 3/4] sched: Move cpu load stats functions above fair queue callbacks Frederic Weisbecker
2016-01-13 16:01 ` [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue Frederic Weisbecker
2016-01-19 13:17 ` Peter Zijlstra [this message]
2016-01-19 17:03 ` Frederic Weisbecker
2016-01-20 9:09 ` Peter Zijlstra
2016-01-20 14:54 ` Frederic Weisbecker
2016-01-20 15:11 ` Thomas Gleixner
2016-01-20 15:19 ` Christoph Lameter
2016-01-20 16:52 ` Frederic Weisbecker
2016-01-20 16:45 ` Frederic Weisbecker
2016-01-20 16:56 ` Peter Zijlstra
2016-01-20 17:21 ` Frederic Weisbecker
2016-01-20 18:25 ` Peter Zijlstra
2016-01-21 13:25 ` Frederic Weisbecker
2016-01-20 9:03 ` Thomas Gleixner
2016-01-20 14:31 ` Frederic Weisbecker
2016-01-20 14:43 ` Thomas Gleixner
2016-01-20 16:40 ` Frederic Weisbecker
2016-01-20 16:42 ` Christoph Lameter
2016-01-20 16:47 ` Frederic Weisbecker
2016-01-14 21:19 ` [RFC PATCH 0/4] sched: Improve cpu load accounting with nohz Dietmar Eggemann
2016-01-14 21:27 ` Peter Zijlstra
2016-01-14 22:23 ` Dietmar Eggemann
2016-01-15 7:07 ` Byungchul Park
2016-01-15 16:56 ` Dietmar Eggemann
2016-01-18 0:23 ` Byungchul Park
2016-01-19 13:04 ` Peter Zijlstra
2016-01-20 0:48 ` Byungchul Park
2016-01-20 13:04 ` Dietmar Eggemann
2016-02-29 11:14 ` [tip:sched/core] sched/fair: Avoid using decay_load_missed() with a negative value tip-bot for Byungchul Park
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