From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Sander Subject: Re: 3.12.6-rt9 on AM335x (armv7) Date: Tue, 07 Jan 2014 09:38:49 +0100 Message-ID: <15611103.51LOkxSQt9@dabox> References: <52C44448.3030405@ma-fu.de> <52CB0881.9000502@ma-fu.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users To: Matthias Fuchs Return-path: Received: from lvps176-28-13-145.dedicated.hosteurope.de ([176.28.13.145]:59274 "EHLO lvps176-28-13-145.dedicated.hosteurope.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755167AbaAGIp1 convert rfc822-to-8bit (ORCPT ); Tue, 7 Jan 2014 03:45:27 -0500 In-Reply-To: <52CB0881.9000502@ma-fu.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hi > after some chatting with Nicholas and being sure that I didn't do any= thing > totally stupid I would like to provide my current kernel config and a= trace > generated by "cyclictest ... -b500". >=20 > kernel config -> https://www.dropbox.com/s/zsud0b77xoosjm1/config > trace -> > https://www.dropbox.com/s/5uf58oqo0qwcn4x/trace-cyclictest-2508us.txt >=20 > I still get max latencies of about 4000us on this TI AM335x system ru= nning > 3.12.6-rt9 with timers-do-not-raise-softirq-unconditionally.patch rev= erse > applied. >=20 > sched_rt_runtime_us and sched_rt_period_us are identical. The system = is idle > during the test. Rootfilesystem comes via NFS. >=20 > root@generic-armv7a:~# cat /proc/sys/kernel/sched_rt_runtime_us > 1000000 > root@generic-armv7a:~# cat /proc/sys/kernel/sched_rt_period_us > 1000000 >=20 > root@generic-armv7a:~# uname -a > Linux generic-armv7a 3.12.6-rt9-dirty #3 SMP PREEMPT RT Sat Jan 4 23:= 01:19 > CET 2014 armv7l GNU/Linux >=20 > root@generic-armv7a:~# ~/cyclictest -p99 -m -n -i200 -h400 -q -l10000= 0 -b > 500 # /dev/cpu_dma_latency set to 0us > INFO: debugfs mountpoint: /sys/kernel/debug/tracing/ > could not set ftrace_enabled to 0 > could not set tracing_max_latency to 0 > # Histogram > ... > # Total: 000018604 > # Min Latencies: 00024 > # Avg Latencies: 00158 > # Max Latencies: 02508 Wohaa, thats bad for a latency patched kernel. Have you disabled=20 powermanagement? I have an older rt patched kernel and it was not too g= ood. If i remember correctly it was between 100-200=B5s latency. But thats far better than this. You could also load the system with hackbench, if= its=20 the idle pm than latency would get better. Best regards Tim -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html