From: John Kacur <jkacur@redhat.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Punit Agrawal <punitagrawal@gmail.com>,
Clark Williams <williams@redhat.com>,
Pierre FICHEUX <pierre.ficheux@smile.fr>,
linux-rt-users@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Strange problem with PREEMPT_RT
Date: Thu, 30 Sep 2021 10:59:48 -0400 (EDT) [thread overview]
Message-ID: <dabf30d5-283d-72f6-6fd9-33bc1be0c87c@redhat.com> (raw)
In-Reply-To: <87v92i9o5t.fsf@jogness.linutronix.de>
On Thu, 30 Sep 2021, John Ogness wrote:
> On 2021-09-30, Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> >> With hackbench, the system is sufficiently busy to avoid the going
> >> into idle.
> >
> > Not just that. cyclictest's usage of /dev/cpu_dma_latency has the side
> > effect that it may disable some of the PM stuff in the system.
> > So your system appears good but then when cyclictest is gone, the
> > numbers go up.
> >
> > Maybe we should drop that so we observe a system without altering its
> > behaviour?
>
> +1
>
> Developers wanting to explicitly cause this behavior can use --latency=
> to enable it. Having it on as a default is misleading.
>
> John Ogness
>
If you pass "--laptop" to cyclictest then it won't use the trick of
writing to /dev/cpu_dma_latency in order to save battery power.
It doesn't matter whether you are really running on a laptop or not.
John Kacur
next prev parent reply other threads:[~2021-09-30 14:59 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 16:40 Strange problem with PREEMPT_RT Pierre FICHEUX
2021-09-30 0:13 ` Punit Agrawal
2021-09-30 8:21 ` Pierre FICHEUX
2021-09-30 13:17 ` Luis Goncalves
2021-09-30 13:18 ` Sebastian Andrzej Siewior
2021-09-30 13:23 ` Sebastian Andrzej Siewior
2021-09-30 13:26 ` Pierre FICHEUX
2021-09-30 13:51 ` Sebastian Andrzej Siewior
2021-09-30 14:31 ` Pierre FICHEUX
2021-09-30 23:40 ` Punit Agrawal
2021-10-03 11:11 ` Jack Winch
2021-10-04 12:54 ` John Kacur
2021-10-18 9:12 ` Sebastian Andrzej Siewior
2021-09-30 13:41 ` John Ogness
2021-09-30 14:25 ` John Kacur
2021-09-30 15:02 ` John Ogness
2021-09-30 15:49 ` Sebastian Andrzej Siewior
2021-09-30 16:16 ` John Kacur
2021-09-30 23:22 ` Punit Agrawal
2021-09-30 14:59 ` John Kacur [this message]
2021-09-30 23:01 ` Punit Agrawal
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