On 1/5/15 10:55 AM, Tom Easterday wrote: > I have a DN2800MT Atom motherboard that I want to run Linuxcnc on. I am > using a Mesa 6I25 for step/dir so I am not much worried about latency. I > know this board isn't ideal, but in the past I recall measuring latency of > around 33k-40k or so which was fine. I did that with an older version of > Linuxcnc (I think 2.5.X) after setting the isolcpus=1 parameter. Yesterday I > put the latest Linuxcnc from the LiveCD on this system - version 2.6.5 on > Wheezy (and did software updates afterwards). I launched the latency app, > one instance of glxgears, and went home. This morning I see the following > > Servo thread Max Jitter: 770360 > Base thread Max Jitter: 771712
Ouch! > I recalled that I need to set isolcpus this morning so I went to read about > that here and the last thing on the page > (http://wiki.linuxcnc.org/cgi-bin/wiki.pl?The_Isolcpus_Boot_Parameter_And_GRUB2) > says this will no longer be required "in the near future"? Does the latest > need this parameter set, and is that my problem, or is this not required, and > if so, why would the latency be so different than it was in 2.5? I dont know about any effort to make isolcpus not required any more. There is no difference in latency between different versions of LinuxCNC, what matters is the RTAI kernel version. If you're running from the 2.6 Live/Install Image, you'll be running the new RTAI kernel, which has very different latency behaviors on some hardware. Use lstopo to see what vcpus share the L2 cache of the last vcpu, then use isolcpus to isolate them all. That may help. Maybe memleak (Alec, our RTAI expert) can help identify any other things to try? -- Sebastian Kuzminsky ------------------------------------------------------------------------------ Dive into the World of Parallel Programming! The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
