them. Move windows around on the screen. Motherboards, video cards, USB ports, and stepping. Additional command line tools are availalbe for examining latency Hi Regards multicore latency reduction - just done some quick tests and I am not able to reproduce the results. If the numbers are 100 uS or more (100,000 nanoseconds), then the PC is not a good candidate for software stepping. Testing for two days with CPU burn test, multiple glxgears, streaming youtube during whole test. Installed from Live CD (Debian, Onboard display 1920x1200 32GB ram KDE dphys-swapfile - Kernel commandline "quiet text isolcpus=2,3" - Buster PREEMPT_RT, 1 GB RAM, Debian Wheezy on HDD,Dissabled Onboard Sound&COM Ports, Disabled energy saving modes, 2 GB Ram, Debian Wheezy live USB, this box didn't run well on 8.04 or 10.04, either, 749MB RAM, 6GB HD, port 0x3BC, must boot with lapic option (details. Follow the BasicSteps to edit pages. A so-called low latency network connection is one that generally experiences small delay times, while a high latency connection generally suffers from long delays. You can now decide if you want to use the whole disk or install alongside Windows XP. You definitely want to see why the read latency is so high, and why reads are occurring in the first place. No Legacy set. VESA driver. timing reference for the step pulses. Multiple YouTube, Ubuntu10.04LTS 2.6.32-122-rtai kernel 2GB RAM, 30GB SATA/SSD, hyperthreading disabled, PS/2 keyboard and mouse, no isolcpus parameter, test ran 15m with 2Xglxgears, web surfing, taking directory listing of external USB HD, playing movie from external HD in VLC, Ubuntu10.04LTS 2.6.32-122-rtai kernel 2GB RAM, 30GB SATA/SSD, hyperthreading disabled, PS/2 keyboard and mouse, isolcpus=1 parameter, same test as above, Ubuntu10.04LTS 2.6.32-122-rtai kernel 2GB RAM, 30GB SATA/SSD, hyperthreading disabled, no keyboard and mouse, isolcpus=1 parameter, running headless with Gnome and X shut down, same test as above while logged in via ssh -Y from remote computer, Bios A.M. 1014.006, 1GB SDRam, Intel 82865 controller, Radeon X300 with 128MB, 4 GB Corsair PC2-800 CL4 RAM, 80GB Samsung IDE HDD, applied tweaks for multicore IRQ remapping (, Nvidia 6600GT with binary driver, on SMP kernel, Note there is a ~40k latency spike when *starting* openGL windows, all results are with GLX gears running, as well as xchat and firefox while installing a bunch of software, 10.04LTS installed from LiveCD, onboard ATI Radeon 4250 video, 4GB RAM, C1E off in bios, 3-hour latency-test run with usual torture tests, 10.04LTS installed from LiveCD, onboard ATI Radeon 4250 video, 4GB RAM, C1E off in bios, isolcpus=3, 3-hour latency-test run with usual torture tests, 10.04LTS, Defaults in BIOS glxgears, Surf web, youtube videos, 10.04LTS, ATI/AMD Radeon XFX HD 5450 512MB C1E off in bios, instances of "gzip -c /dev/urandom > /dev/null" to load up CPUs to 100%, 10.04LTS, onboard Graphics 512MB, C1E off in bios, instances of "gzip -c /dev/urandom > /dev/null" to load up CPUs to 100%, Ubuntu 10.01 Live CD, PNY PCI-E GeForce 7300 256mb, Ubuntu 10.04 LTS, 2G DDR2 1066 Ram (2) 1g sticks, Mesa 5i20, onboard Intel GMA X4500 Video, Intel G41 Chipset, Disabled ACPI, everything just worked, 512mB RAM, AGP video card running "vesa" driver (STG4000 [3D Prophet Kyro Series] (rev 01)). What can be done about improving latency? Lots of small packets might also cause high interrupts (even though those might be simulated as well?). To run the test, open a terminal window eric81 says: September 11, 2014 at 3:49 pm. The lower the latency, the BASE_THREAD that makes the periodic heartbeat that serves as a 4GB RAM, Ubuntu 10.04 LTS, EIST off, C1E off, Spread Spectrum off, Disable Audio and network support, On-board video, Running GLXGEARS and reading PDFs. Measured 33 Watts total power draw by Mini-ITX computer running. Also set fan to Enhanced - on all the time so no temp sensing- otherwise will have 64 sec spikes like smi, but smi module will not work with this chipset), Debian Wheezy, 2 GB RAM, Mainboard D2151 μATX, onboard GPU, Mesa 5i25 (Sound, LAN, PWM, DVD, Floppy, Card reader, Frontpanel & unused Ports disabled), Gentoo 3.4.55 RTAI, 8GB RAM with PAE, All power management disabled in BIOS, Disabled Spread Spectrum, Turbo Core, APM, C6, Cool'n'quiet, SVM, Cpu Throttle, Suspend to RAM, Athlon Dual Core 4850e and onboard graphic, 6GB Ram + Booted from 8.04 LiveCD + 10*Glxgears + 1hour, Onboard graphics, 8GB Ram, 10.04, 2.6.32 RTAI, All power management disabled in BIOS, Kernel options "isolcpus=1 acpi_irq_nobalance noirqbalance", Upstart script "irq-affinity.conf" to /etc/init, 3.2 GB RAM, Integrated AMD HD 6310 graphics with 384 MB, AMD Catalyst Version 10.12., Ubuntu 10.04, 2.6.32-122-rtai kernel, isolcpus=1, 1 hour test, 4 GB Kingston KHX1600C9D3K2/4GX RAM, 64GB OCZ Agility SSD, applied tweaks for multicore IRQ remapping, tested for 24 hours with 2 glxgears and flash/text firefox browser running, 2 GB RAM, BIOS:CPU MULTI=DISABLED CPU SMARTFAN=DISABLED Azealea and other unused devices=DISABLED, noirqbalance grub mod, 2 glxgears for 2 hours, 4 GB RAM, BIOS:CPU advance CPU settings all disabled, SMI enabled, no isolcpu used, tested with burnP5 and a big glxgears for 20 minutes, 4 GB RAM, BIOS:CPU advance CPU settings all disabled, SMI enabled, no isolcpu used, tested with burnP6 and 4 GLX gears, and focing the cpu in other ways with flash, and moving big files, 2 GB DDR2 800 Mhz. I also leave speedstep on on most PC and laptops so not to have the processors running at full blast generating heat unnecessary, if the latency does not sky rocket. respond to an external request. ATI 3D Rage IIC AGP Card. The most common signs of high latency include: Your data takes a long time to send, as in an email with a large attachment You should see the test produce some pretty unusably high numbers. Test run for 7h with glxgears (and screensaver). If you are going to use software stepping, then read this: Lousy with 6.06. Even a little packet loss on a high latency link tends to hurt bandwidth quite a bit. Play some music. Test load and machine configuration as per: Dual Ethernet card, dual parport card, Radeon HD3450, 2 ram sticks. Just about every PC has a parallel port that is faster you can run the heartbeat, and the faster and smoother the Results may vary by 1000 ns from one invocation to another (e.g., by a few microseconds). glxgears running @ 390 fps. Based on the speed of light alone (299,792,458 meters/second), there is a latency of 3.33 microseconds (0.000001 of a second) for every kilometer of path covered. a number of other things can hurt the latency. If the Max Jitter is more like 30-50 microseconds, you can still get good results, but your maximum step rate might be a little disappointing, especially if you use microstepping or have very fine pitch leadscrews. than the latest and fastest P4 Hyperthreading beast. The standard test in LinuxCNC is checking the BASE period latency (even though we are not using a base period). The lower the latency, the faster you can run the heartbeat, and the faster and smoother the step pulses will be. The CPU isn’t the only factor in determining latency. Open Firefox and check you have connection to the internet then choose Install from the desktop. fixable, see http://wiki.linuxcnc.org/cgi-bin/wiki.pl?FixingSMIIssues. There are two normal factors that significantly influence the latency of a consumer device (like a cable modem, dsl modem or dial-up modem). TroubleShooting - what to check if something fails Hardware Problems - known hardware with problems and possible fixes Latency-test - real-time performance database FixingSMIIssues - fixing SMI issues that cause high latency StepMotorWireIdentification - Stepper Wire Identification This test is the first test that should be performed on a PC Latency around 20 μs is near the upper limit for successful software step generation at any reasonable pace; the LinuxCNC description has more details. » Reduce high latency - Fix lag by online games and online application. 3COM Fast Etherlink XL PCI. thread. SSD, 2 GB 667 MHz RAM. Latency is also referred to as a ping rate and typically measured in milliseconds (ms). Also tested with no CPUs isolated, but running four "cpu hogs". (In Ubuntu, from Applications → Accessories → Terminal) Installing Debian Stretch on the machine the M2 and nic were both detected and all was well. Latency was higher than 10.04 but nonetheless it ran the 201 Gecko much better than 10.04, 1 GB Ram, 8.04 Live CD (wouldn't run 10.04), 1 GB Ram, Debian Wheezy live USB, note ran decent on 8.04 but crap on Wheezy. etc.UPDATE:- USB issue fixed with Debian Wheezy based distro with 3.4.55-4-rtai kernel - still be aware that BIOS upgrade may be required before it can be used with linux, AMD Athlon II X2 245, 2Gb Ram Radeon HD 3000 onboard video @1280x1024, 10.04LTS LiveCD, nVidia GT215(GeForce GT 240), HT enabled in BIOS, 8 CPUs shown to OS. For details, see, http://sourceforge.net/mailarchive/forum.php?thread_name=5b3301cccd23%241a33e5e0%244e9bb1a0%24%40d-silva.org&forum_name=emc-users, http://www.linuxcnc.org/index.php/german/forum/18-computer/25927-reducing-latency-on-multicore-pcs-success?start=10#36865, http://support.lenovo.com/en_US/detail.page?LegacyDocID=MIGR-58185, https://www.cnet.com/products/lenovo-thinkcentre-m58-7359-core-2-duo-e7400-2-8-ghz, http://www.intel.com/products/desktop/motherboards/D945gclf2/D945gclf2-overview.htm, http://www.jetway.com.tw/jetway/system/productshow2, https://forum.linuxcnc.org/18-computer/25927-reducing-latency-on-multicore-pc-s-success?limitstart=0, https://copr.fedorainfracloud.org/coprs/dwrobel/kernel-rt/, 4GB Ram, onboard display, 500gb SSD, LiveCD. kernel options: isolcpus=1 lapic quiet rootdelay=5 intel_idle.max_cstate=0 processor.max_cstate=0 idle=poll. If you let the Computer run for about 30 min. Running 8.04 with stock 2.6.24-16-rtai kernel, long latency test (IMPORTANT - Must turn off all power management APM - suspend etc so all shown Disabled. when you do some particular action. Onboard Graphics without problem Debian Wheezy Went from jitter of over 1,000,000 to 25000 with the BIOS rollback. each and every time can give better results For LinuxCNC the request is If See disk I/O latency using the default values and the current directory $ ioping . Everything disabled in bios. See these pages: Alhough being simulated -- this is a bit strange. For instance, one Intel 4GB Ram, isolcpus=1, C1E/C3/C6 suspend states disabled in BIOS, ATI Radeon 2400HD w/ "radeon" driver. 4GB Ram, Radeon HD 7350, Seagate Barracuda 1TB 7200rpm, Ubuntu 12.04.4 LTS, GRUB 1.99-21ubuntu3.14, "isolcpus=1,2,3", with "cpu hog" running, 3 GLXGEARS, surfing web, listening to music, system monitor running, and making this entry. nanoseconds), then the PC is not a good candidate for software Latency is how long it takes the PC to stop what it is doing and It can be useful to think of preemption as a way to reduce scheduler latency. seconds it had a very bad 300 us latency. also have some disadvantages: The best way to find out how well your PC will lrun LinuxCNC Booting the current LinuxCNC iso image and running the latency-test gave about 3200 idle and 5100 under load. > > I to have seen the problem regarding USB and latency on my mill and > plasma table. In the example above, latency-test only ran for a few seconds. 3COM Fast Etherlink XL PCI. Firstly create a network bridge that can be placed inbetween the test network and its router (assuming eth0 and eth1 are the bridged interfaces).. To increase network latency use the following command: For details, see WhatLatencyTestDoes. With LinuxCNC, the computer’s CPU handles the step pulses (in some cases – see below), so any delay (i.e. For LinuxCNC the request is BASE_THREAD that makes the periodic heartbeat that serves as a timing reference for the step pulses. Latency is how long it takes the PC to stop what it is doing and respond to an external request. If you press the test base period jitter button, this launches the latency test window (you can also load this directly from the applications/cnc panel). VT enabled. 4GB RAM, On board video, Ubuntu 10.04 LTS installed from LiveCD, 2 GB Ram, Ubuntu 8.04, same machine as above. Onboard Graphics without problem DeLock. 4Gb RAM. Numbers over 1 millisecond (1,000,000 nanoseconds) mean the PC is not a good candidate for LinuxCNC, regardless of whether you use software stepping or not. The best way to find out what you are dealing with is to run the RTAI latency test. capable of outputting step pulses that are generated by the software. get good results, but your maximum step rate might be a little Even when updated reports of complete incompatibility with rtai kernels, usb does not work etc. Motherboards, video cards, USB ports, and a number of other things can hurt the latency. Sinlge HDD and CD-ROM. This test is important to setting up the controller to run your machine. Once the messages arrive on Earth, however, the page loads quickly, like on other high-bandwidth internet connections (such as DSL and cable internet). LinuxCNCKnowledgeBase | RecentChanges | PageIndex | Preferences | LinuxCNC.org This page is read-only. 1. TweakingSoftwareStepGeneration, Latency-test comes with LinuxCNC, you can run it with 'latency-test' from the prompt. Low profile desktop with mini ATX board and Intel 82801EB/ER (ICH5/ICH5R) chipset & 82865G graphics. Note that the numbers reported in this test are extremely precise but not necessarily extremely reproducible. Reducing clock multiplicator from 9 to 8 improved latency. On some i have to turn it off. On-board i915 graphics. When you try 15.5 us, you find that the computer is sluggish, so you settle on 16 us. So, what do the results mean? Boot parameters "lapic quiet rootdelay=5 isolcpus=1 idle=poll acpi_irq_nobalance noirqbalance" and tweaked irq affinity as here (. disappointing, especially if you use microstepping or have very than about 15-20 microseconds (15000-20000 nanoseconds), the Source: How To Geek Updating the firmware often increases the bandwidth speed and reduces latency.Just like software updates, the firmware updates too can help revive an old router.

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