Results of latency test, list of computers tested for use with LinuxCNC

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06 Oct 2020 10:40 #185048 by tommylight

seuchato wrote: Quite astonishing that the results with hd give better results than with ssd!
I guess, tommylight would agree: really usable.

On both counts, i agree.

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07 Oct 2020 16:15 #185271 by txtrone
I ran this script on a new PC I am building. I am not sure I have all the BIOS settings correct, but this is what I got with Buster.
LinuxCNC pc tests, version 20200930, started 06.10.2020 22:08:57
********************************************************************************
General info:
Supermicro,  Super Server
Bios version 1.2a, dated 02/20/2020
Chipset: Intel Corporation Q370 
Harddisk is non-rotational, ie. SSD
The amount of swap currently used is 0
================================================================================
CPU related data:
model name	: Intel(R) Pentium(R) Gold G5420 CPU @ 3.80GHz
cpu cores	: 2
stepping	: 10
cache size	: 4096 KB
================================================================================
RAM related data:
Maximum Capacity: 64 GB
Maximum Voltage: 1.2 V
Maximum Voltage: Unknown
Size: 16384 MB
Non-Volatile Size: None
Volatile Size: 16 GB
Cache Size: None
Logical Size: None
Size: 16384 MB
Non-Volatile Size: None
Volatile Size: None
Cache Size: None
Logical Size: None
================================================================================
GPU related data:
product: Intel Corporation
configuration: driver=i915 latency=0
================================================================================
Parallel port related data:
number of parallel ports is 0
================================================================================
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-latency

Desktop environment : xfce4
Windowmanager       : Xfwm4
Displaymanager      : lightdm
================================================================================
Kernel related data:
Kernel 4.19.0-10-rt-amd64
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
Cpu idle driver: intel_idle
================================================================================
Kernel modules data:
Check if pcspkr is loaded: No, which is good!
Check if snd modules are loaded: No, which is good!
================================================================================
Keyboard & Mouse related data:
Number of mice: 1
Mouse 0 : PixArt USB Optical Mouse
Mice  attached to USB:
Keyboards attached to USB:
SiGma Micro Keyboard TRACER Gamma Ivory
================================================================================
LinuxCNC related data:
LinuxCNC version is: 2.8.0
================================================================================
Preparing for latency test:
Started glxgears No. 1, 2, 3, 4, 5
..........
Started firefox with 'https://vimeo.com/150574260', WID 50331651
================================================================================
Command for latency test is:
su newpc -c  "latency-histogram --nobase  --sbinsize 1000 --nox 2>&1 | tee -a 1602040135.lat &"

Latency testing loop started Tue 06 Oct 2020 10:09:09 PM CDT, 
should end after Wed 07 Oct 2020 12:09:09 AM CDT

================================================================================
Swap useage: prerun: 0, running: 0

================================================================================
CPU core temperatures:
Core 0: Tmin: 33.0°C, Tmax: 45.0°C, (high = +78.0°C, crit = +100.0°C)
Core 1: Tmin: 34.0°C, Tmax: 45.0°C, (high = +78.0°C, crit = +100.0°C)
================================================================================
last latency data is as follows:.
 7201 secs  servo min: -80.200 uS max:  82.600 uS sdev:   5.300 uS
 7202 secs  servo min: -80.200 uS max:  82.600 uS sdev:   5.300 uS
The following user(s) said Thank You: seuchato

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07 Oct 2020 19:43 #185297 by txtrone
Same 'new build' as above. All BIOS settings the same. This time loaded Mint 19.3
LinuxCNC pc tests, version 20200930, started 07.10.2020 12:18:04
********************************************************************************
General info:
Supermicro,  Super Server
Bios version 1.2a, dated 02/20/2020
Chipset: Harddisk is non-rotational, ie. SSD
The amount of swap currently used is 0
================================================================================
CPU related data:
model name	: Intel(R) Pentium(R) Gold G5420 CPU @ 3.80GHz
cpu cores	: 2
stepping	: 10
cache size	: 4096 KB
================================================================================
RAM related data:
Maximum Capacity: 64 GB
Maximum Voltage: 1.2 V
Maximum Voltage: Unknown
Size: 16384 MB
Size: 16384 MB
================================================================================
GPU related data:
product: Intel Corporation
configuration: driver=i915 latency=0
================================================================================
Parallel port related data:
number of parallel ports is 0
================================================================================
Os and desktop related data:
PRETTY_NAME="Linux Mint 19.3"

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-latency

Desktop environment : lightdm
Windowmanager       : Xfwm4
Displaymanager      : lightdm
================================================================================
Kernel related data:
Kernel 4.19.106-rt46-lcnc
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
Cpu idle driver: intel_idle
================================================================================
Kernel modules data:
Check if pcspkr is loaded: No, which is good!
Check if snd modules are loaded: No, which is good!
================================================================================
Keyboard & Mouse related data:
Number of mice: 1
Mouse 0 : PixArt USB Optical Mouse
Mice  attached to USB:
Keyboards attached to USB:
SiGma Micro Keyboard TRACER Gamma Ivory
================================================================================
LinuxCNC related data:
LinuxCNC version is: 2.8.0.53.gacb5793e4
================================================================================
Preparing for latency test:
Started glxgears No. 1, 2, 3, 4, 5
..........
Started firefox with 'https://vimeo.com/150574260', WID 69206019
================================================================================
Command for latency test is:
su newpc -c  "latency-histogram --nobase  --sbinsize 1000 --nox 2>&1 | tee -a 1602091083.lat &"

Latency testing loop started Wed Oct  7 12:18:18 CDT 2020, 
should end after Wed Oct  7 14:18:18 CDT 2020

================================================================================
Swap useage: prerun: 0, running: 0

================================================================================
CPU core temperatures:
Core 0: Tmin: 39.0°C, Tmax: 48.0°C, (high = +78.0°C, crit = +100.0°C)
Core 1: Tmin: 39.0°C, Tmax: 47.0°C, (high = +78.0°C, crit = +100.0°C)
================================================================================
last latency data is as follows:.
 7201 secs  servo min: -57.600 uS max:  60.700 uS sdev:   2.000 uS
 7202 secs  servo min: -57.600 uS max:  60.700 uS sdev:   2.000 uS
The following user(s) said Thank You: seuchato, tommylight

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07 Oct 2020 23:07 #185312 by txtrone
Same setup, I added an M.2 SSD drive and the latency took a hit.
LinuxCNC pc tests, version 20200930, started 07.10.2020 16:03:39
********************************************************************************
General info:
Supermicro,  Super Server
Bios version 1.2a, dated 02/20/2020
Chipset: Harddisk is non-rotational, ie. SSD
The amount of swap currently used is 0
================================================================================
CPU related data:
model name	: Intel(R) Pentium(R) Gold G5420 CPU @ 3.80GHz
cpu cores	: 2
stepping	: 10
cache size	: 4096 KB
================================================================================
RAM related data:
Maximum Capacity: 64 GB
Maximum Voltage: 1.2 V
Maximum Voltage: Unknown
Size: 16384 MB
Size: 16384 MB
================================================================================
GPU related data:
product: Intel Corporation
configuration: driver=i915 latency=0
================================================================================
Parallel port related data:
number of parallel ports is 0
================================================================================
Os and desktop related data:
PRETTY_NAME="Linux Mint 19.3"

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-latency

Desktop environment : lightdm
Windowmanager       : Xfwm4
Displaymanager      : lightdm
================================================================================
Kernel related data:
Kernel 4.19.106-rt46-lcnc
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
Cpu idle driver: intel_idle
================================================================================
Kernel modules data:
Check if pcspkr is loaded: No, which is good!
Check if snd modules are loaded: No, which is good!
================================================================================
Keyboard & Mouse related data:
Number of mice: 1
Mouse 0 : PixArt USB Optical Mouse
Mice  attached to USB:
Keyboards attached to USB:
SiGma Micro Keyboard TRACER Gamma Ivory
================================================================================
LinuxCNC related data:
LinuxCNC version is: 2.8.0.53.gacb5793e4
================================================================================
Preparing for latency test:
Started glxgears No. 1, 2, 3, 4, 5
..........
Started firefox with 'https://vimeo.com/150574260', WID 73400353
================================================================================
Command for latency test is:
su newpc -c  "latency-histogram --nobase  --sbinsize 1000 --nox 2>&1 | tee -a 1602104617.lat &"

Latency testing loop started Wed Oct  7 16:03:52 CDT 2020, 
should end after Wed Oct  7 18:03:52 CDT 2020

================================================================================
Swap useage: prerun: 0, running: 0

================================================================================
CPU core temperatures:
Core 0: Tmin: 36.0°C, Tmax: 49.0°C, (high = +78.0°C, crit = +100.0°C)
Core 1: Tmin: 36.0°C, Tmax: 49.0°C, (high = +78.0°C, crit = +100.0°C)
================================================================================
last latency data is as follows:.
 7202 secs  servo min: -76.100 uS max:  79.200 uS sdev:   5.300 uS
 7203 secs  servo min: -76.100 uS max:  79.200 uS sdev:   5.300 uS
The following user(s) said Thank You: seuchato

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08 Oct 2020 03:59 #185325 by BeagleBrainz
It would be interesting to see the fstab for the HDD vs the SSD. One would think the SSD would have a lower impact on latency.
Any details of the model of each ?

What is the amount of cache for each device ?

Bearing in mind if I have this right:
What are the diffs if you start the actual latency test and then start open GLX gears & firefox. As I see it open GLX & Firefox after would show any issues with file access.
Then we could see the affect of having noatime,nodiratime in fstab and not having those options.

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08 Oct 2020 08:21 #185339 by tommylight
Lately i have gotten some new 240GB SSD, cheap ones, and noticed some very strange issues with them:
During speed test the read and write times will be OK for about 5 to 7 sec then they will plummet to bellow sea level for a sec then go up a bit but not where they were at the beginning of the test.
The access times will vary a lot.
During normal use they work fine, except at random they will lock the PC stiff for a short time and move on like nothing happened. This happens several times during daily use.
All this makes me think they have very slow flash nand chips and use another level of caching inside.

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08 Oct 2020 08:48 #185340 by BeagleBrainz
I've had no trouble with Kingston and lately I've been using Crucial MX series. In the Odroid I have a Crucial P1 series NVME and no issues.

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08 Oct 2020 09:04 #185342 by Mike_Eitel
This behaviour of ssd is well known and handled in several test reports. All is depending from the size and the implementation of chaching. Cheepo means often worser solution.

In test you often generate as much acces as possible, so chachelines fill up sooner or later. But i don't believe a 'normal in use lcnc' generates so much disk access.

But i'm also astonished that latency should be higher with ssd. Are different disk drivers used in linux for hdd and ssd. Does any expert knows something?
Mike
The following user(s) said Thank You: seuchato

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09 Oct 2020 05:11 #185425 by seuchato
Would an output like this be helpul?
lsblk -d -o PATH,NAME,VENDOR,MODEL,PKNAME
PATH     NAME VENDOR   MODEL            PKNAME
/dev/sda sda  ATA      WDC WD101KRYZ-01 
/dev/sdb sdb  ATA      WDC WD101KRYZ-01 
/dev/sdc sdc  ATA      SanDisk SDSSDA24 
/dev/sdd sdd  ATA      SanDisk SDSSDA24 
/dev/sdj sdj  LITEONIT  LCS-256M6S      
/dev/sdk sdk                            
/dev/sr0 sr0  Optiarc  DVD RW AD-7201S
greez
chris

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09 Oct 2020 05:15 #185426 by seuchato

BeagleBrainz wrote: It would be interesting to see the fstab for the HDD vs the SSD. One would think the SSD would have a lower impact on latency.
Any details of the model of each ?

What is the amount of cache for each device ?

Bearing in mind if I have this right:
What are the diffs if you start the actual latency test and then start open GLX gears & firefox. As I see it open GLX & Firefox after would show any issues with file access.
Then we could see the affect of having noatime,nodiratime in fstab and not having those options.


I could add an option to show fstab and lsblock info to the script. There could also be an option to run the script for an amount of time w/o any glxgears or firefox. Would that be helpfull?

greez
chris

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