From: "Doug Smythies" <dsmythies@telus.net>
To: 'Thomas Ilsche' <thomas.ilsche@tu-dresden.de>
Cc: "'Rafael J. Wysocki'" <rjw@rjwysocki.net>,
'Thomas Gleixner' <tglx@linutronix.de>,
'Paul McKenney' <paulmck@linux.vnet.ibm.com>,
'Rik van Riel' <riel@surriel.com>,
'Peter Zijlstra' <peterz@infradead.org>,
'Aubrey Li' <aubrey.li@linux.intel.com>,
'Mike Galbraith' <mgalbraith@suse.de>,
'Frederic Weisbecker' <fweisbec@gmail.com>,
'LKML' <linux-kernel@vger.kernel.org>,
Doug Smythies <dsmythies@telus.net>,
'Linux PM' <linux-pm@vger.kernel.org>
Subject: RE: [RFT][PATCH v5 7/7] cpuidle: menu: Avoid selecting shallow states with stopped tick
Date: Mon, 19 Mar 2018 11:21:58 -0700 [thread overview]
Message-ID: <003301d3bfaf$2d5e4090$881ac1b0$@net> (raw)
In-Reply-To: xuDHe5JrTQdbpxuDMeg0da
On 2018.03.19 05:47 Thomas Ilsche wrote:
> On 2018-03-15 23:19, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> If the scheduler tick has been stopped already and the governor
>> selects a shallow idle state, the CPU can spend a long time in that
>> state if the selection is based on an inaccurate prediction of idle
>> time. That effect turns out to be noticeable, so it needs to be
>> mitigated.
>
> What are some common causes for that situation?
> How could I trigger this for testing?
It appeared quite readily with my simple 100% load
on one CPU test. Back then (V3) there only 6 patches in the set,
and before the re-spin there ended up being a patch 7 of 6, which
made a significant difference in both package power and the
histograms of times in each idle state.
Reference:
https://marc.info/?l=linux-pm&m=152075419526696&w=2
... Doug
next prev parent reply other threads:[~2018-03-19 18:21 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-15 21:59 [RFT][PATCH v5 0/7] sched/cpuidle: Idle loop rework Rafael J. Wysocki
2018-03-15 22:03 ` [RFT][PATCH v5 1/7] time: tick-sched: Reorganize idle tick management code Rafael J. Wysocki
2018-03-15 22:05 ` [RFT][PATCH v5 2/7] sched: idle: Do not stop the tick upfront in the idle loop Rafael J. Wysocki
2018-03-15 22:07 ` [RFT][PATCH v5 3/7] sched: idle: Do not stop the tick before cpuidle_idle_call() Rafael J. Wysocki
2018-03-15 22:11 ` [RFT][PATCH v5 4/7] cpuidle: Return nohz hint from cpuidle_select() Rafael J. Wysocki
2018-03-19 9:11 ` Peter Zijlstra
2018-03-19 9:39 ` Rafael J. Wysocki
2018-03-15 22:13 ` [RFT][PATCH v5 5/7] sched: idle: Select idle state before stopping the tick Rafael J. Wysocki
2018-03-15 22:16 ` [RFT][PATCH v5 6/7] cpuidle: menu: Refine idle state selection for running tick Rafael J. Wysocki
2018-03-19 9:45 ` Peter Zijlstra
2018-03-19 9:49 ` Rafael J. Wysocki
2018-03-15 22:19 ` [RFT][PATCH v5 7/7] cpuidle: menu: Avoid selecting shallow states with stopped tick Rafael J. Wysocki
2018-03-19 12:47 ` Thomas Ilsche
2018-03-19 18:21 ` Doug Smythies [this message]
2018-03-20 17:15 ` Doug Smythies
2018-03-20 17:28 ` Rafael J. Wysocki
2018-03-17 12:42 ` [RFT][PATCH v5 0/7] sched/cpuidle: Idle loop rework Thomas Ilsche
2018-03-17 16:11 ` Doug Smythies
2018-03-18 11:00 ` Rafael J. Wysocki
2018-03-18 16:15 ` Rafael J. Wysocki
2018-03-19 10:49 ` Peter Zijlstra
2018-03-19 11:36 ` Rafael J. Wysocki
2018-03-19 11:58 ` Rafael J. Wysocki
2018-03-19 12:31 ` Peter Zijlstra
2018-03-20 10:01 ` Thomas Ilsche
2018-03-20 10:49 ` Rafael J. Wysocki
2018-03-20 17:15 ` Doug Smythies
2018-03-20 21:03 ` Doug Smythies
2018-03-21 6:33 ` Rafael J. Wysocki
2018-03-21 13:51 ` Doug Smythies
2018-03-21 13:58 ` Rafael J. Wysocki
2018-03-18 15:30 ` Doug Smythies
2018-03-18 16:06 ` Rafael J. Wysocki
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