* [Flent-users] irtt sleep test
@ 2017-12-07 1:24 Dave Taht
2017-12-07 8:36 ` Pete Heist
0 siblings, 1 reply; 2+ messages in thread
From: Dave Taht @ 2017-12-07 1:24 UTC (permalink / raw)
To: flent-users, Pete Heist
good test. I wish I'd thought of it. Life below a ms is a PITA.
For comparison, an aarch64 and an x86_64:
root@nanopineo2:~# irtt sleep
Testing sleep accuracy...
Sleep Duration Mean Error % Error
1ns 13.353µs 1335336.9
10ns 14.34µs 143409.5
100ns 13.343µs 13343.9
1µs 12.791µs 1279.2
10µs 148.661µs 1486.6
100µs 150.907µs 150.9
1ms 168.001µs 16.8
10ms 131.235µs 1.3
100ms 145.611µs 0.1
200ms 162.917µs 0.1
500ms 169.885µs 0.0
d@nemesis:~$ irtt sleep
Testing sleep accuracy...
Sleep Duration Mean Error % Error
1ns 668ns 66831.9
10ns 672ns 6723.7
100ns 557ns 557.6
1µs 57.749µs 5774.9
10µs 63.063µs 630.6
100µs 67.737µs 67.7
1ms 153.978µs 15.4
10ms 169.709µs 1.7
100ms 186.685µs 0.2
200ms 176.859µs 0.1
500ms 177.271µs 0.0
--
Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619
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* Re: [Flent-users] irtt sleep test
2017-12-07 1:24 [Flent-users] irtt sleep test Dave Taht
@ 2017-12-07 8:36 ` Pete Heist
0 siblings, 0 replies; 2+ messages in thread
From: Pete Heist @ 2017-12-07 8:36 UTC (permalink / raw)
To: Dave Taht; +Cc: flent-users
Thanks for the numbers. I wondered if irtt would run on that Archer.
1ms seems to be a kind of timing purgatory, where above that things look good, below that are the demon-things and right at 1ms it’s a mixture. There’s usually some discontinuity in percent error around 1us or 100ns like in your numbers. Below some point I guess you’re just testing cpu / system call overhead. I was going to remove those lower numbers then figured it’s fun to look at anyway.
Macs don’t seem to do as well as Linux at 1ms and above, which is what spawned the timer compensation stuff. The ‘hybrid’ timer can be useful still down to 100us or so, and the ‘busy’ timer is currently needed for anything below that. Looks like timerfds could be good down to 5us or so, without a modified kernel:
https://stackoverflow.com/questions/19927225/scheduling-events-at-microsecond-granularity-in-posix
OS/X 10.11.6, Core i7-2860QM (quad core late 2011):
tron:~/src/github.com/peteheist/irtt:% ./irtt sleep
Testing sleep accuracy...
Sleep Duration Mean Error % Error
1ns 381ns 38194.1
10ns 370ns 3703.5
100ns 286ns 286.6
1µs 9.041µs 904.2
10µs 30.538µs 305.4
100µs 60.746µs 60.7
1ms 263.256µs 26.3
10ms 2.000929ms 20.0
100ms 3.309786ms 3.3
200ms 4.183972ms 2.1
500ms 2.53946ms 0.5
> On Dec 7, 2017, at 2:24 AM, Dave Taht <dave.taht@gmail.com> wrote:
>
> good test. I wish I'd thought of it. Life below a ms is a PITA.
>
> For comparison, an aarch64 and an x86_64:
>
> root@nanopineo2:~# irtt sleep
>
> Testing sleep accuracy...
>
> Sleep Duration Mean Error % Error
>
> 1ns 13.353µs 1335336.9
>
> 10ns 14.34µs 143409.5
>
> 100ns 13.343µs 13343.9
>
> 1µs 12.791µs 1279.2
>
> 10µs 148.661µs 1486.6
>
> 100µs 150.907µs 150.9
>
> 1ms 168.001µs 16.8
>
> 10ms 131.235µs 1.3
>
> 100ms 145.611µs 0.1
>
> 200ms 162.917µs 0.1
>
> 500ms 169.885µs 0.0
>
>
> d@nemesis:~$ irtt sleep
>
> Testing sleep accuracy...
>
>
> Sleep Duration Mean Error % Error
>
> 1ns 668ns 66831.9
>
> 10ns 672ns 6723.7
>
> 100ns 557ns 557.6
>
> 1µs 57.749µs 5774.9
>
> 10µs 63.063µs 630.6
>
> 100µs 67.737µs 67.7
>
> 1ms 153.978µs 15.4
>
> 10ms 169.709µs 1.7
>
> 100ms 186.685µs 0.2
>
> 200ms 176.859µs 0.1
>
> 500ms 177.271µs 0.0
>
>
> --
>
> Dave Täht
> CEO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-669-226-2619
_______________________________________________
Flent-users mailing list
Flent-users@flent.org
http://flent.org/mailman/listinfo/flent-users_flent.org
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