From: Stanislav Meduna <stano@meduna.org>
To: "linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>
Subject: i.MX28 milliseconds latencies, interrupts disabled in arch_cpu_idle?
Date: Thu, 17 Apr 2014 22:38:48 +0200 [thread overview]
Message-ID: <53503BD8.8000506@meduna.org> (raw)
Hi,
on a i.MX28:
Linux nxt 3.12.15-rt25+ #83 PREEMPT RT Thu Apr 17 20:54:00 CEST 2014 armv5tejl GNU/Linux
# tracer: irqsoff
#
# irqsoff latency trace v1.1.5 on 3.12.15-rt25+
# --------------------------------------------------------------------
# latency: 2224 us, #6/6, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0)
# -----------------
# | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
# -----------------
# => started at: rcu_idle_enter
# => ended at: arch_cpu_idle
#
#
# _--------=> CPU#
# / _-------=> irqs-off
# | / _------=> need-resched
# || / _-----=> need-resched_lazy
# ||| / _----=> hardirq/softirq
# |||| / _---=> preempt-depth
# ||||| / _--=> preempt-lazy-depth
# |||||| / _-=> migrate-disable
# ||||||| / delay
# cmd pid |||||||| time | caller
# \ / |||||||| \ | /
<idle>-0 0d...1.. 2us+: rcu_idle_enter
<idle>-0 0d...2.. 11us+: T.796 <-rcu_idle_enter
<idle>-0 0d...2.. 17us!: arch_cpu_idle <-cpu_startup_entry
<idle>-0 0d...1.. 2219us+: arch_cpu_idle
<idle>-0 0d...1.. 2234us+: trace_hardirqs_on <-arch_cpu_idle
<idle>-0 0d...1.. 2303us : <stack trace>
=> arch_cpu_idle
=> cpu_startup_entry
=> start_kernel
Why are interrupts disabled here (and are they really disabled)?
$ egrep "IDLE|SMP|HZ" .config
CONFIG_BROKEN_ON_SMP=y
CONFIG_HZ_PERIODIC=y
# CONFIG_NO_HZ_IDLE is not set
# CONFIG_NO_HZ is not set
CONFIG_GENERIC_SMP_IDLE_THREAD=y
CONFIG_GENERIC_IDLE_POLL_SETUP=y
CONFIG_HZ_FIXED=0
# CONFIG_HZ_100 is not set
# CONFIG_HZ_200 is not set
CONFIG_HZ_250=y
# CONFIG_HZ_300 is not set
# CONFIG_HZ_500 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=250
# CONFIG_CPU_IDLE is not set
# CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED is not set
Configuring
CONFIG_CPU_IDLE=y
CONFIG_CPU_IDLE_GOV_LADDER=y
does not help
Maybe it is just some tracing infrastructure interference - the effect
of enabling the tracing is huge on this platform for some reason.
Just enabling the irqsoff tracing makes the machine unsuitable
for any serious load.
Thanks
--
Stano
next reply other threads:[~2014-04-17 20:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-17 20:38 Stanislav Meduna [this message]
2014-04-18 16:09 ` i.MX28 milliseconds latencies, interrupts disabled in arch_cpu_idle? Tim Sander
2014-04-18 18:12 ` Stanislav Meduna
2014-04-18 22:21 ` Stanislav Meduna
2014-04-19 21:24 ` Tim Sander
2014-04-21 9:00 ` Stanislav Meduna
2014-04-19 10:36 ` Gilles Chanteperdrix
2014-04-21 9:11 ` Stanislav Meduna
2014-04-21 10:09 ` Gilles Chanteperdrix
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=53503BD8.8000506@meduna.org \
--to=stano@meduna.org \
--cc=linux-rt-users@vger.kernel.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.