linux-rt-users.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Clark Williams <williams@redhat.com>
Cc: Stefan Roese <stefan.roese@gmail.com>, linux-rt-users@vger.kernel.org
Subject: Re: cyclictest better values with system load than without (OMAP3530 target)
Date: Fri, 29 Nov 2013 13:56:23 +0100	[thread overview]
Message-ID: <20131129125623.GB31099@linutronix.de> (raw)
In-Reply-To: <20131126101232.21636c8f@sluggy>

* Clark Williams | 2013-11-26 10:12:32 [-0600]:

>In my experience (on x86_64 mainly), that behavior (worse times when
>not under load) is due to the overhead of coming out of power-save/idle
>states. When you've got a big load on the system and all the cores are
>active, then the power-save logic and/or the idle logic doesn't kick in
>and devices aren't being powered down.
This is the case here, too. The overhead comming out of a deep power
state plus the invalidated caches.

>Do you know if your OMAP has power-save logic available? Alternatively
>do you know how expensive the idle mechanism is? Have you tried booting
>with idle=poll then measuring without a load?

idle=pull is x86 only. Disable the complete PM stuff should solve the
issue. You could go via arch_cpu_idle() to check what is used.
The idle routine should come either via cpuidle_idle_call() or arm_pm_idle().

>Clark

Sebastian

  reply	other threads:[~2013-11-29 12:56 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-26  9:21 cyclictest better values with system load than without (OMAP3530 target) Stefan Roese
2013-11-26 14:21 ` Dmitry Lysenko
2013-11-26 19:14   ` Stefan Roese
2013-11-26 20:14     ` Tim Sander
2013-11-26 16:12 ` Clark Williams
2013-11-29 12:56   ` Sebastian Andrzej Siewior [this message]
2013-11-29 15:10     ` Carsten Emde
2013-11-29 16:36       ` Gilles Chanteperdrix
2013-11-29 16:58         ` Gilles Chanteperdrix
2013-11-29 17:36           ` Carsten Emde
2013-11-29 19:34             ` Gilles Chanteperdrix
2013-11-29 21:10               ` Carsten Emde

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20131129125623.GB31099@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=linux-rt-users@vger.kernel.org \
    --cc=stefan.roese@gmail.com \
    --cc=williams@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).