From: Stefan Jenisch <stefan.jenisch@gmail.com>
To: linux-rt-users@vger.kernel.org
Subject: Difficulties with cyclictest on AMD CPU
Date: Sun, 27 Apr 2014 13:01:08 +0200 [thread overview]
Message-ID: <535CE374.7050907@gmail.com> (raw)
Hello folks!
I am having some difficulties with cyclictest on an “AMD GX-210HA SOC
with Radeon(tm) HD Graphics” CPU. Latency values are better with some
CPU load (execution of an endless loop) than without.
When running the command “cyclictest -c 0 -t15 -p 95 -i 500 -n -l
100000” I get the output:
policy: fifo: loadavg: 0.25 0.09 0.06 1/201 2349
T: 0 ( 2335) P:95 I:500 C: 100000 Min: 11 Act: 19 Avg: 21 Max: 231
T: 1 ( 2336) P:95 I:1000 C: 50000 Min: 10 Act: 13 Avg: 23 Max: 222
T: 2 ( 2337) P:95 I:1500 C: 33333 Min: 11 Act: 19 Avg: 24 Max: 198
T: 3 ( 2338) P:95 I:2000 C: 25000 Min: 10 Act: 16 Avg: 25 Max: 185
T: 4 ( 2339) P:95 I:2500 C: 20000 Min: 12 Act: 22 Avg: 25 Max: 196
T: 5 ( 2340) P:95 I:3000 C: 16666 Min: 11 Act: 20 Avg: 23 Max: 233
T: 6 ( 2341) P:95 I:3500 C: 14285 Min: 12 Act: 19 Avg: 25 Max: 209
T: 7 ( 2342) P:95 I:4000 C: 12500 Min: 10 Act: 13 Avg: 25 Max: 123
T: 8 ( 2343) P:95 I:4500 C: 11111 Min: 11 Act: 65 Avg: 29 Max: 203
T: 9 ( 2344) P:95 I:5000 C: 10000 Min: 11 Act: 26 Avg: 22 Max: 175
T:10 ( 2345) P:95 I:5500 C: 9091 Min: 13 Act: 30 Avg: 31 Max: 165
T:11 ( 2346) P:95 I:6000 C: 8333 Min: 12 Act: 19 Avg: 23 Max: 161
T:12 ( 2347) P:95 I:6500 C: 7692 Min: 12 Act: 19 Avg: 24 Max: 194
T:13 ( 2348) P:95 I:7000 C: 7142 Min: 12 Act: 64 Avg: 23 Max: 185
T:14 ( 2349) P:95 I:7500 C: 6666 Min: 12 Act: 20 Avg: 23 Max: 192
Now the thing is when getting the CPUs a little bit busy with something
else(e.g. simultaneous running “while true; do echo loop; done” on in
another shell) the same cyclictest results in:
root@host:[~]# cyclictest -c 0 -t15 -p 95 -i 500 -n -l 100000
policy: fifo: loadavg: 1.78 0.54 0.22 3/203 2431
T: 0 ( 2417) P:95 I:500 C: 100000 Min: 10 Act: 19 Avg: 16 Max: 44
T: 1 ( 2418) P:95 I:1000 C: 49998 Min: 10 Act: 16 Avg: 15 Max: 45
T: 2 ( 2419) P:95 I:1500 C: 33335 Min: 9 Act: 16 Avg: 15 Max: 33
T: 3 ( 2420) P:95 I:2000 C: 25000 Min: 10 Act: 14 Avg: 16 Max: 40
T: 4 ( 2421) P:95 I:2500 C: 20000 Min: 10 Act: 15 Avg: 16 Max: 33
T: 5 ( 2422) P:95 I:3000 C: 16667 Min: 10 Act: 15 Avg: 16 Max: 60
T: 6 ( 2423) P:95 I:3500 C: 14286 Min: 10 Act: 14 Avg: 16 Max: 35
T: 7 ( 2424) P:95 I:4000 C: 12500 Min: 12 Act: 24 Avg: 16 Max: 33
T: 8 ( 2425) P:95 I:4500 C: 11111 Min: 11 Act: 15 Avg: 16 Max: 34
T: 9 ( 2426) P:95 I:5000 C: 10000 Min: 10 Act: 15 Avg: 17 Max: 46
T:10 ( 2427) P:95 I:5500 C: 9091 Min: 10 Act: 15 Avg: 15 Max: 38
T:11 ( 2428) P:95 I:6000 C: 8333 Min: 10 Act: 13 Avg: 15 Max: 35
T:12 ( 2429) P:95 I:6500 C: 7692 Min: 11 Act: 13 Avg: 16 Max: 42
T:13 ( 2430) P:95 I:7000 C: 7143 Min: 11 Act: 12 Avg: 16 Max: 32
T:14 ( 2431) P:95 I:7500 C: 6666 Min: 11 Act: 15 Avg: 17 Max: 37
As can be seen the max-latency improved!
It’s like ordering in an empty restaurant. Takes hours to get the dinner
if you are the only customer. As soon as some more people are around
everything is getting faster...
So my guess is that the cpu goes into some sort of powersave mode from
time to time. The wakeup from these powersave state results in
latencies. Currently I am looking for a proper solution to this problem
and what I have tried so far:
- BIOS upgrade
- Upgraded to linux-3.10.12-rt25
- Disabling all sort of powersave modes in the kernel config
- Activated cpufreq-performance (which seems to be ignored anyway)
- Searched the BIOS for any powersave modes to deactivate (none found)
I got rather clueless on what else to try! Does anyone has a helping
hint on how to solve this one???
With many thanks in advance,
Stefan J.
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next reply other threads:[~2014-04-27 11:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-27 11:01 Stefan Jenisch [this message]
2014-04-28 14:24 ` Difficulties with cyclictest on AMD CPU Clark Williams
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=535CE374.7050907@gmail.com \
--to=stefan.jenisch@gmail.com \
--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 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).