ubuntu10.04 Lcnc 2.7 rtai error
24 Oct 2015 00:50 #64192
by PCW
Replied by PCW on topic ubuntu10.04 Lcnc 2.7 rtai error
I believe that you are seeing a caching issue
My experience with Preempt-RT and our Ethernet cards show the same thing,
the faster you set the servo thread, the faster you _can_ set the servo thread
because the LRU cache algorithm keeps the main RT parts cached if they are
accessed frequently enough
I have also noticed that CPUs with larger caches have better RTAI and Preempt-RT performance
Here's a fast CPU with a 3M cache:
Preempt-RT
freeby.mesanet.com/h97-g3258-preemt-rt.png
RTAI
freeby.mesanet.com/g3258-rtai.png
My experience with Preempt-RT and our Ethernet cards show the same thing,
the faster you set the servo thread, the faster you _can_ set the servo thread
because the LRU cache algorithm keeps the main RT parts cached if they are
accessed frequently enough
I have also noticed that CPUs with larger caches have better RTAI and Preempt-RT performance
Here's a fast CPU with a 3M cache:
Preempt-RT
freeby.mesanet.com/h97-g3258-preemt-rt.png
RTAI
freeby.mesanet.com/g3258-rtai.png
The following user(s) said Thank You: bkt
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24 Oct 2015 01:10 #64193
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
@ ArkEyes .. for experience I try to run latency with arguments ....
@PCW ... than if try the same config with asrock Q1900B-itx (intel 4 core 2M chache) I've the better result ...
My problem at the end si that .... as suggest PCW I try halscope ... noew with 2 channel fo encoder ... but not see nothings eccepts the 2 signal .... 8000 samples at 1Khz .... Wicth is the command to run halscope at 10Khz for example??... I can change by hand the value of jogwheel encoder!
Anyhow ... the realtime issue is show in axis (in touchy too??) and if the error is not a real problem how do you disable the error message so that it is never seen ?
Regards
Giorgio
@PCW ... than if try the same config with asrock Q1900B-itx (intel 4 core 2M chache) I've the better result ...
My problem at the end si that .... as suggest PCW I try halscope ... noew with 2 channel fo encoder ... but not see nothings eccepts the 2 signal .... 8000 samples at 1Khz .... Wicth is the command to run halscope at 10Khz for example??... I can change by hand the value of jogwheel encoder!
Anyhow ... the realtime issue is show in axis (in touchy too??) and if the error is not a real problem how do you disable the error message so that it is never seen ?
Regards
Giorgio
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24 Oct 2015 01:30 #64194
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
latency-test 1ms from my 17:45 (forum hour) to now (surfing, 3 youtube windows): servo thread 1ms Max Jitter 38404 .... and no go up if run some other program ....
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24 Oct 2015 15:24 - 24 Oct 2015 15:24 #64210
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
After 16 hour of youtube html5 and flash player videos, running bash script for open and close a program .... latency-test 1ms = 44932 ....
Tonight I've a doubt .... than today i've create a config with stepconf and parallel port ..... I make a bash for launch and close it (100 time) ... never see the realtime error ..... than try to launch mymachineconf (with mesa 5i25 + 7i77) at 2° time have the error 5/6 sec after the launch .....
that means something ?
Regards
giorgio
Tonight I've a doubt .... than today i've create a config with stepconf and parallel port ..... I make a bash for launch and close it (100 time) ... never see the realtime error ..... than try to launch mymachineconf (with mesa 5i25 + 7i77) at 2° time have the error 5/6 sec after the launch .....
that means something ?
Regards
giorgio
Last edit: 24 Oct 2015 15:24 by bkt.
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24 Oct 2015 22:24 #64217
by PCW
Replied by PCW on topic ubuntu10.04 Lcnc 2.7 rtai error
It means that the 1 MS thread has experienced >200 usec delays occasionally
It may be that you dont have real time errors in the parallel port case because the base
thread keeps the cache filled with RT code.
On poor RT hardware (and I consider all Atoms up to Baytrail quite poor)
You might try ArcEyes trick of running a dummy base thread
I might note that I do not see any RT errors on my D510 running a 1 KHz thread
(and its run Mesa hardware continuously for years at a time)
It might be related to the Power VR graphics in the CedarView (D2xxx) series Atoms
It may be that you dont have real time errors in the parallel port case because the base
thread keeps the cache filled with RT code.
On poor RT hardware (and I consider all Atoms up to Baytrail quite poor)
You might try ArcEyes trick of running a dummy base thread
I might note that I do not see any RT errors on my D510 running a 1 KHz thread
(and its run Mesa hardware continuously for years at a time)
It might be related to the Power VR graphics in the CedarView (D2xxx) series Atoms
The following user(s) said Thank You: bkt
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25 Oct 2015 01:51 - 25 Oct 2015 01:55 #64235
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
@PCW --- your suggestion at last is buy a motherboard with cpu with more cache and greater frequecy .... Is right? You can suggest an quite good cpu and motherboard? (consider my choice for now is ubuntu 10.04 .... with debian before we have to play a little longer and completely skip wheezy )
if that's what you suggest seems the lesser evil. I'll wait for your confirmation.
Regards
giorgio
if that's what you suggest seems the lesser evil. I'll wait for your confirmation.
Regards
giorgio
Last edit: 25 Oct 2015 01:55 by bkt.
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27 Oct 2015 23:38 #64361
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
@ arkEye or @PCW is possible that the problem (rtai error on start up only with mesa5i25) is become from buffered RAM. My ram isn't buffered but in asrock j1900-itx not work (crucial ddr3 ram as ad2550b motherboard) ... I've read some post where someone suggest not use crucial ddr3 because it has some kind of buffer anyhow ....
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27 Oct 2015 23:44 #64362
by PCW
Replied by PCW on topic ubuntu10.04 Lcnc 2.7 rtai error
Not likely this is RAM related at all
Do you have issues with the J1900 or just the D2550?
Do you have issues with the J1900 or just the D2550?
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30 Oct 2015 21:53 #64523
by bkt
Replied by bkt on topic ubuntu10.04 Lcnc 2.7 rtai error
The J1900 have a wrong ram because not start at all.
Instead I try with H97M gigabyte and I3 3Ghz 4° gen.
All ok .... whit any type of trik on rtai and cpu, withous disable sometings from bios, whit 6 glgears whindows and 2 firefox youtube open after 2 hour obtain
servo thread 1ms 10580
base thread 25usec 11900
I think if I block 1 CPU for linuxcnc an disable any things from bios all system work perfectly .
No see at all rtai error message. ..... Ubuntu 10.04 linuxcnc 2.7
regards
giorgio
Instead I try with H97M gigabyte and I3 3Ghz 4° gen.
All ok .... whit any type of trik on rtai and cpu, withous disable sometings from bios, whit 6 glgears whindows and 2 firefox youtube open after 2 hour obtain
servo thread 1ms 10580
base thread 25usec 11900
I think if I block 1 CPU for linuxcnc an disable any things from bios all system work perfectly .
No see at all rtai error message. ..... Ubuntu 10.04 linuxcnc 2.7
regards
giorgio
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31 Oct 2015 00:04 #64527
by PCW
Replied by PCW on topic ubuntu10.04 Lcnc 2.7 rtai error
IMHO
I would toss out Ubuntu 10.04 as its no longer maintained and use Wheezy
I would not bother with isolcpus at all as it will just slow the system down to gain a few usec better latency
With hardware stepgens and servo systems, any latency in the 0 to 50 usec range is absolutely fine,
there is really no point in getting better (and up to 500 usec can be OK with the right hardware setup)
I would toss out Ubuntu 10.04 as its no longer maintained and use Wheezy
I would not bother with isolcpus at all as it will just slow the system down to gain a few usec better latency
With hardware stepgens and servo systems, any latency in the 0 to 50 usec range is absolutely fine,
there is really no point in getting better (and up to 500 usec can be OK with the right hardware setup)
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