* [Xenomai] Why get low latency while running stress command?
@ 2018-06-13 8:51 Kiwamu Okabe
2018-06-13 10:47 ` Lange Norbert
0 siblings, 1 reply; 3+ messages in thread
From: Kiwamu Okabe @ 2018-06-13 8:51 UTC (permalink / raw)
To: xenomai
Dear all,
I build Xenomai kernel on Debian GNU/Linux Stretch (amd64) with attached config.
It runs on Intel(R) Celeron(R) CPU J3355 @ 2.00GHz.
But the latency is not good:
```
$ sudo /usr/lib/xenomai/testsuite/latency
== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD| 0.912| 6.856| 414.649| 104| 0| 0.912| 414.649
RTD| 6.065| 10.102| 120.338| 109| 0| 0.912| 414.649
RTD| 5.473| 10.465| 124.834| 116| 0| 0.912| 414.649
RTD| 6.224| 10.215| 137.833| 125| 0| 0.912| 414.649
RTD| 6.058| 10.392| 126.856| 131| 0| 0.912| 414.649
RTD| 1.126| 8.278| 239.556| 145| 0| 0.912| 414.649
RTD| 4.789| 9.966| 122.924| 149| 0| 0.912| 414.649
RTD| 5.228| 10.289| 126.303| 157| 0| 0.912| 414.649
RTD| 5.470| 10.273| 126.994| 165| 0| 0.912| 414.649
RTD| 5.624| 10.391| 127.353| 171| 0| 0.912| 414.649
RTD| 1.128| 10.766| 429.696| 245| 0| 0.912| 429.696
RTD| 5.568| 10.557| 123.488| 249| 0| 0.912| 429.696
RTD| 2.113| 8.890| 253.340| 282| 0| 0.912| 429.696
RTD| 6.056| 10.301| 126.958| 285| 0| 0.912| 429.696
RTD| 6.230| 10.411| 127.802| 293| 0| 0.912| 429.696
RTD| 5.787| 10.447| 124.719| 299| 0| 0.912| 429.696
RTD| 6.143| 10.307| 126.947| 301| 0| 0.912| 429.696
RTD| 6.250| 10.391| 124.367| 303| 0| 0.912| 429.696
RTD| 5.861| 10.367| 126.357| 309| 0| 0.912| 429.696
```
Strangely the result gets better while running stress command:
```
$ stress -v -c 8 -i 10 -d 8 &
$ sudo /usr/lib/xenomai/testsuite/latency
== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD| 2.744| 4.108| 8.634| 0| 0| 2.744| 8.634
RTD| 2.872| 4.225| 8.670| 0| 0| 2.744| 8.670
RTD| 3.147| 4.250| 8.538| 0| 0| 2.744| 8.670
RTD| 2.767| 4.271| 10.512| 0| 0| 2.744| 10.512
RTD| 2.867| 4.239| 8.502| 0| 0| 2.744| 10.512
RTD| 2.826| 4.262| 9.819| 0| 0| 2.744| 10.512
RTD| 2.930| 4.222| 9.128| 0| 0| 2.744| 10.512
RTD| 2.840| 4.159| 8.984| 0| 0| 2.744| 10.512
RTD| 2.841| 4.112| 8.608| 0| 0| 2.744| 10.512
RTD| 2.828| 4.112| 8.557| 0| 0| 2.744| 10.512
RTD| 2.875| 4.124| 8.662| 0| 0| 2.744| 10.512
RTD| 2.795| 4.109| 9.112| 0| 0| 2.744| 10.512
RTD| 2.939| 4.103| 8.677| 0| 0| 2.744| 10.512
RTD| 2.867| 4.123| 8.686| 0| 0| 2.744| 10.512
RTD| 2.808| 4.106| 8.728| 0| 0| 2.744| 10.512
RTD| 2.940| 4.113| 8.488| 0| 0| 2.744| 10.512
RTD| 2.873| 4.132| 8.703| 0| 0| 2.744| 10.512
RTD| 2.994| 4.107| 8.479| 0| 0| 2.744| 10.512
RTD| 2.983| 4.147| 8.642| 0| 0| 2.744| 10.512
```
What's wrong? Should I set some kernel settings?
Best regards,
--
Kiwamu Okabe at METASEPI DESIGN
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai] Why get low latency while running stress command?
2018-06-13 8:51 [Xenomai] Why get low latency while running stress command? Kiwamu Okabe
@ 2018-06-13 10:47 ` Lange Norbert
2018-06-14 5:42 ` Kiwamu Okabe
0 siblings, 1 reply; 3+ messages in thread
From: Lange Norbert @ 2018-06-13 10:47 UTC (permalink / raw)
To: Kiwamu Okabe, xenomai
Hi,
I guess what happens is, that the CPU will be put to sleep and/or lower frequency and voltage between calls,
These transitions are rather slow and will then have to happen on wake-up
Disable any kind of powersaving features in Linux and possibly BIOS (C-States).
Kind regards,
Norbert
-----Original Message-----
From: Xenomai <xenomai-bounces@xenomai.org> On Behalf Of Kiwamu Okabe
Sent: Mittwoch, 13. Juni 2018 10:51
To: xenomai@xenomai.org
Subject: [Xenomai] Why get low latency while running stress command?
E-MAIL FROM A NON-ANDRITZ SOURCE: AS A SECURITY MEASURE, PLEASE EXERCISE CAUTION WITH E-MAIL CONTENT AND ANY LINKS OR ATTACHMENTS.
Dear all,
I build Xenomai kernel on Debian GNU/Linux Stretch (amd64) with attached config.
It runs on Intel(R) Celeron(R) CPU J3355 @ 2.00GHz.
But the latency is not good:
```
$ sudo /usr/lib/xenomai/testsuite/latency
== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD| 0.912| 6.856| 414.649| 104| 0| 0.912| 414.649
RTD| 6.065| 10.102| 120.338| 109| 0| 0.912| 414.649
RTD| 5.473| 10.465| 124.834| 116| 0| 0.912| 414.649
RTD| 6.224| 10.215| 137.833| 125| 0| 0.912| 414.649
RTD| 6.058| 10.392| 126.856| 131| 0| 0.912| 414.649
RTD| 1.126| 8.278| 239.556| 145| 0| 0.912| 414.649
RTD| 4.789| 9.966| 122.924| 149| 0| 0.912| 414.649
RTD| 5.228| 10.289| 126.303| 157| 0| 0.912| 414.649
RTD| 5.470| 10.273| 126.994| 165| 0| 0.912| 414.649
RTD| 5.624| 10.391| 127.353| 171| 0| 0.912| 414.649
RTD| 1.128| 10.766| 429.696| 245| 0| 0.912| 429.696
RTD| 5.568| 10.557| 123.488| 249| 0| 0.912| 429.696
RTD| 2.113| 8.890| 253.340| 282| 0| 0.912| 429.696
RTD| 6.056| 10.301| 126.958| 285| 0| 0.912| 429.696
RTD| 6.230| 10.411| 127.802| 293| 0| 0.912| 429.696
RTD| 5.787| 10.447| 124.719| 299| 0| 0.912| 429.696
RTD| 6.143| 10.307| 126.947| 301| 0| 0.912| 429.696
RTD| 6.250| 10.391| 124.367| 303| 0| 0.912| 429.696
RTD| 5.861| 10.367| 126.357| 309| 0| 0.912| 429.696
```
Strangely the result gets better while running stress command:
```
$ stress -v -c 8 -i 10 -d 8 &
$ sudo /usr/lib/xenomai/testsuite/latency
== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD| 2.744| 4.108| 8.634| 0| 0| 2.744| 8.634
RTD| 2.872| 4.225| 8.670| 0| 0| 2.744| 8.670
RTD| 3.147| 4.250| 8.538| 0| 0| 2.744| 8.670
RTD| 2.767| 4.271| 10.512| 0| 0| 2.744| 10.512
RTD| 2.867| 4.239| 8.502| 0| 0| 2.744| 10.512
RTD| 2.826| 4.262| 9.819| 0| 0| 2.744| 10.512
RTD| 2.930| 4.222| 9.128| 0| 0| 2.744| 10.512
RTD| 2.840| 4.159| 8.984| 0| 0| 2.744| 10.512
RTD| 2.841| 4.112| 8.608| 0| 0| 2.744| 10.512
RTD| 2.828| 4.112| 8.557| 0| 0| 2.744| 10.512
RTD| 2.875| 4.124| 8.662| 0| 0| 2.744| 10.512
RTD| 2.795| 4.109| 9.112| 0| 0| 2.744| 10.512
RTD| 2.939| 4.103| 8.677| 0| 0| 2.744| 10.512
RTD| 2.867| 4.123| 8.686| 0| 0| 2.744| 10.512
RTD| 2.808| 4.106| 8.728| 0| 0| 2.744| 10.512
RTD| 2.940| 4.113| 8.488| 0| 0| 2.744| 10.512
RTD| 2.873| 4.132| 8.703| 0| 0| 2.744| 10.512
RTD| 2.994| 4.107| 8.479| 0| 0| 2.744| 10.512
RTD| 2.983| 4.147| 8.642| 0| 0| 2.744| 10.512
```
What's wrong? Should I set some kernel settings?
Best regards,
--
Kiwamu Okabe at METASEPI DESIGN
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai] Why get low latency while running stress command?
2018-06-13 10:47 ` Lange Norbert
@ 2018-06-14 5:42 ` Kiwamu Okabe
0 siblings, 0 replies; 3+ messages in thread
From: Kiwamu Okabe @ 2018-06-14 5:42 UTC (permalink / raw)
To: xenomai
Dear Lange,
On Wed, Jun 13, 2018 at 7:47 PM, Lange Norbert
<norbert.lange@andritz.com> wrote:
> I guess what happens is, that the CPU will be put to sleep and/or lower frequency and voltage between calls,
> These transitions are rather slow and will then have to happen on wake-up
> Disable any kind of powersaving features in Linux and possibly BIOS (C-States).
Thanks for your reply.
After read following:
* https://www.thomas-krenn.com/en/wiki/Processor_P-states_and_C-states
* https://gist.github.com/wmealing/2dd2b543c4d3cff6cab7
* https://wiki.archlinux.org/index.php/CPU_frequency_scaling#Scaling_governors
* https://wiki.debian.org/HowTo/CpuFrequencyScaling
I set up some parameters:
```
$ sudo vi /etc/default/grub
--snip--
GRUB_CMDLINE_LINUX_DEFAULT="quiet processor.max_cstate=1
intel_idle.max_cstate=0"
--snip--
$ sudo update-grub
$ sudo apt install cpufrequtils
$ sudo vi /etc/default/cpufrequtils
GOVERNOR="performance"
$ sudo reboot
```
Then I have better latency:
```
$ sudo /usr/lib/xenomai/testsuite/latency
== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD| 0.417| 2.658| 4.211| 0| 0| 0.417| 4.211
RTD| 0.843| 2.718| 4.780| 0| 0| 0.417| 4.780
RTD| 0.726| 2.689| 4.456| 0| 0| 0.417| 4.780
RTD| 0.923| 2.731| 5.068| 0| 0| 0.417| 5.068
RTD| 0.908| 2.676| 4.906| 0| 0| 0.417| 5.068
RTD| 0.402| 2.686| 4.784| 0| 0| 0.402| 5.068
RTD| 0.907| 2.617| 4.501| 0| 0| 0.402| 5.068
RTD| 0.928| 2.615| 5.730| 0| 0| 0.402| 5.730
RTD| 0.538| 2.630| 4.245| 0| 0| 0.402| 5.730
RTD| 0.399| 2.638| 4.607| 0| 0| 0.399| 5.730
RTD| 0.414| 2.613| 4.114| 0| 0| 0.399| 5.730
RTD| 0.502| 2.620| 4.486| 0| 0| 0.399| 5.730
RTD| 0.694| 2.625| 4.292| 0| 0| 0.399| 5.730
RTD| 0.618| 2.641| 4.847| 0| 0| 0.399| 5.730
```
Thanks a lot!
--
Kiwamu Okabe at METASEPI DESIGN
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2018-06-13 8:51 [Xenomai] Why get low latency while running stress command? Kiwamu Okabe
2018-06-13 10:47 ` Lange Norbert
2018-06-14 5:42 ` Kiwamu Okabe
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