informative. thanks. --- On Thu, 3/8/12, Viesturs Lācis <viesturs.la...@gmail.com> wrote:
> From: Viesturs Lācis <viesturs.la...@gmail.com> > Subject: Re: [Emc-users] EMC2/Ubuntu updates - safe to install? > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Date: Thursday, March 8, 2012, 7:21 AM > 2012/3/8 charles green <xxzzb...@yahoo.com>: > > cnczone - ive seen that before somehow. > > Probably You saw it mentioned in other discussion, where I > posted it, > but did You read it? I had a link in there that explains > Your next > question. > > > the task manager of winxp has a process priority > setting, with one of the choices being 'realtime'. never > tried it for anything. but the realtime mode of operation > in linux is still a general hardware timeshare approach, > no? > > No. > > ..including stuff like keyboard and mouse. > > Definitely no. > I would like to ask someone more knowledgable to explain it > more > precisely, but the main principle is that with RTAI kernel > the tasks > are separated - realtime tasks and all the other tasks. > Keyboard and > mouse are not on realtime, screen output also is not. Also > LinuxCNC > itself is separated between realtime and non-realtime, like > it is > shown here: > http://linuxcnc.org/images/stories/EMC_Control_LG.gif > In theory, if machine runs short on computing power, the > mouse and > keyboard might stop responding, screen might freeze, but > machine will > keep on running the motion precisely. > > And the whole difference from Your examples is that LinuxCNC > follows, > if it is keeping up to be realtime or if it is falling > behind. I > seriously doubt that windoze is measuring and checking, if > it really > meets the requirement for realtime. > If LinuxCNC is falling behind, it displays error on the > screen about > "RTAPI error occured, run Latency test". > INI file specifies the length of base thread and servo > thread in > nanoseconds. And each thread is ran again and again in > repetition, so > what LinuxCNC does is it takes the actual time, taken to > execute the > thread last time, and compares it with the specified number > in INI > file. If the actual time exceeds the requested time, then it > triggers > the error - machine continues working, but user is alerted > that there > was an realtime interrupt. Usually the solution is > increasing the > thread period (especially true for base thread). There is a > Latency > test application, which runs those 2 threads and measures > the timings > and shows the maximum deviation in absolute numbers > (nanoseconds). > > And there is one very very nice feature of Linux realtime > kernel, > which I am sure is not available in windows: isolating CPUs > for > realtime > There is a boot-time parameter "isolcpus" that allows user > to isolate > certain cores of CPU exclusively to realtime tasks. > That is one more thing why I like D510-series ITX boards - > it has > dualcore Atom CPU and I usually isolate one core to > realtime. Reports > from other users show that it considerably improves the > board's > realtime performance (which is good also without this). > > > > 2012/3/8 charles green <xxzzb...@yahoo.com>: > > no, i was talking about commercial production machining > centers, mostly fanuc based, 15-30yr old vintages. > > I cannot think of a better candidate for a LinuxCNC > retrofit... > > Viesturs > > ------------------------------------------------------------------------------ > Virtualization & Cloud Management Using Capacity > Planning > Cloud computing makes use of virtualization - but cloud > computing > also focuses on allowing computing to be delivered as a > service. > http://www.accelacomm.com/jaw/sfnl/114/51521223/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
