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Results of latency test, list of computers tested for use with LinuxCNC
Also, I applied the irq remapping to cpu0 per this post: forum.linuxcnc.org/18-computer/25927-red...lticore-pc-s-success
That change cut the latencies in half.
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- BeagleBrainz
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degreaser wrote: Optiplex 980MT. At this point I'm chasing nanoseconds. This used a non-standard kernel, specifically the rt kernel from xanmod.org/ . The standard kernels are giving good but not quite as good results so far.
Also, I applied the irq remapping to cpu0 per this post: forum.linuxcnc.org/18-computer/25927-red...lticore-pc-s-success
That change cut the latencies in half.
Code:LinuxCNC pc tests, version 20200930, started 06.06.2021 16:56:40 ******************************************************************************** General info: Dell Inc., OptiPlex 980 Bios version A18, dated 02/27/2018 Chipset: Intel Corporation 5 Series/3400 Series Harddisk is non-rotational, ie. SSD The amount of swap currently used is 0 ================================================================================ CPU related data: model name : Intel(R) Core(TM) i5 CPU 650 @ 3.20GHz cpu cores : 2 stepping : 5 cache size : 4096 KB ================================================================================ RAM related data: Maximum Capacity: 16 GB Size: 4096 MB Size: 4096 MB Size: No Module Installed Size: No Module Installed ================================================================================ GPU related data: product: Core Processor Integrated Graphics Controller configuration: driver=i915 latency=0 ================================================================================ Parallel port related data: number of parallel ports is 1 parport0: PC-style at 0x378 (0x778), irq 7, using FIFO [PCSPP,TRISTATE,COMPAT,EPP,ECP] ================================================================================ Os and desktop related data: PRETTY_NAME="Debian GNU/Linux 10 (buster)" Should the info below not match with your machine, kindly post the output of pstree here, including a brief desciption of your desktop environment, window manager and display manager. Tia https://forum.linuxcnc.org/18-computer/39370-script-for-automated-testing-of-computer-l atency Desktop environment : Windowmanager : e16 Displaymanager : lightdm ================================================================================ Kernel related data: Kernel 5.10.41-rt42-xanmod1 GRUB_CMDLINE_LINUX_DEFAULT="quiet isolcpus=1 mitigations=off intel_idle.max_cstate=0 pr ocessor.max_cstate=0 idle=poll acpi_irq_nobalance noirqbalance" Cpu idle driver: none ================================================================================ Kernel modules data: Check if pcspkr is loaded: Yes, may cause bigger latency. can be eliminated using: sudo echo "install pcspkr /bin/true" >/etc/modprobe.d/pcspkr.conf Check if snd modules are loaded: Yes, may cause bigger latency. can probably be disabled in bios, alternatively, you can run "./block-snd-modules" which has just now been created for your convenience. ================================================================================ Keyboard & Mouse related data: Number of mice: 3 Mouse 0 : Logitech USB Optical Mouse Mouse 1 : CHESEN PS2 to USB Converter Mouse Mouse 2 : CHESEN PS2 to USB Converter Mouse Mice attached to USB: Logitech, Inc. M105 Optical Mouse Chesen Electronics Corp. PS/2 Keyboard+Mouse Adapter Keyboards attached to USB: Chesen Electronics Corp. PS/2 Keyboard+Mouse Adapter ================================================================================ LinuxCNC related data: LinuxCNC version is: 2.8.1 ================================================================================ Preparing for latency test: Started glxgears No. 1, 2, 3, 4, 5 .......... Started firefox with 'https://vimeo.com/150574260', WID 14680112 ================================================================================ Command for latency test is: su cadusr -c "latency-histogram --bbinsize 1000 --base 100000 --sbinsize 1000 --nox 2> &1 | tee -a 1623023787.lat &" Latency testing loop started Sun 06 Jun 2021 04:56:54 PM PDT, should end after Sun 06 Jun 2021 06:56:54 PM PDT ================================================================================ Swap useage: prerun: 0, running: 0 ================================================================================ CPU core temperatures: Core 0: Tmin: 37.0°C, Tmax: 41.0°C, (high = +89.0°C, crit = +105.0°C) Core 2: Tmin: 39.0°C, Tmax: 42.0°C, (high = +89.0°C, crit = +105.0°C) ================================================================================ last latency data is as follows:. 7202 secs base min: -9.400 uS max: 9.300 uS sdev: 0.300 uS 7202 secs servo min: -6.900 uS max: 6.900 uS sdev: 0.400 uS
Unless you are after something high speed, and there are better options, I’d stop. For software stepping you have really good numbers. Chasing down nanoseconds isn’t going to get you anything in practical terms.
What would be a great idea is to start your own thread regarding installing the kernel and the changes you made to get those figures. Make mention of your OS and things like that.
Like I said you have some really good numbers there.
In saying all that, I think if you use the noatime option in fstab, it’s the option that doesn’t record when a file was accessed, you might get a slight gain. You might have to check if that is the correct form.
Whilst I haven’t looked into it, reducing the amount of logging could do something. That’s if you feel keen and adventurous.
If you have PS/2 ports available for kb & mouse sometimes the use of them rather than USB can knock a bit off. Tho this might not be an option.
At the end of the day I’d trade stability for the sake of a few 1000ns.
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Also I got my PCIe 1x WiFi NIC (Atheros AR9580 chipset) & installed that.
Net is a slight increase in latency.
With the new NIC I can now disable two of the USB banks. I'll do that, test again, and report back.
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Thanks
-jd
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there is not much in bios, I disabled audio and that's it
result is:
is there anything I can try to make it work with 7i92+7i77 cards?
also, script hangs when trying to read cpu temperature
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- tommylight
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I'm getting unexpected realtime delay on task 0 with period 1000000 and some other errorsConnect the Mesa card and test, should work still.
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