[Emc-developers] Difference RTAI 5.0 <--> PREEMPT-rt ?
Do anybode know the difference between RTAI and PREEMPT-rt? Regards Nicklas Karlsson -- ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
Re: [Emc-developers] Difference RTAI 5.0 <--> PREEMPT-rt ?
Yes, in some words: RTAI is much faster, but relies on the kernel you have, so it is much more complicated to be included in software parts. It is mostly needed only for very high speed applications PREEMPT-RT is a a little bit slower than RTAI, but can be implemented in software much easier, just imagine it is a modul. That is very simple explained, there are more differences. For a normal CNC opperation both should work fine. But if you use i.e. software stepgenerator over a LPT, than take the RTAI. Norbert Am 03.01.2016 um 19:06 schrieb Karlsson & Wang: > Do anybode know the difference between RTAI and PREEMPT-rt? > > Regards Nicklas Karlsson > > -- > ___ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > -- ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
Re: [Emc-developers] Difference RTAI 5.0 <--> PREEMPT-rt ?
Hello, To cut to the core, RTAI is basically an interrupt dispatcher that traps interrupts and re-routes them up either through the RTAI (realtime) modules, or for non realtime tasks back to the Linux kernel. RTAI also provides an API for realtime functions, and floating point operations. The general intent is to run realtime processes in the kernel. PREEMPT-RT is a configuration option for the kernel to add preemption to many more places in the kernel, in particular, it makes the spinlocks preemptable, and it adds a priority tree (priority inheritance). It also includes changes to the high resolution timer code. It does not introduce any API, however all timers in user code are replaced with high resolution timers. There are some issues with PREEMPT-RT and the VGA text console that have not yet been corrected. (Anything that writes to the VGA text console such as printk() introduce large unpredictable latencies.) This patch is intended to run realtime processes in user space, but it also allows realtime kernel modules to be used. -Neil- On Sun, Jan 3, 2016 at 10:06 AM, Karlsson & Wang < nicklas.karls...@karlssonwang.se> wrote: > Do anybode know the difference between RTAI and PREEMPT-rt? > > Regards Nicklas Karlsson > > > -- > ___ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > -- ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
Re: [Emc-developers] Difference RTAI 5.0 <--> PREEMPT-rt ?
On Sun, 3 Jan 2016, Niemand Sonst wrote: > Date: Sun, 3 Jan 2016 19:59:41 +0100 > From: Niemand Sonst <nie...@web.de> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > To: EMC developers <emc-developers@lists.sourceforge.net> > Subject: Re: [Emc-developers] Difference RTAI 5.0 <--> PREEMPT-rt ? > > Yes, > > in some words: > > RTAI is much faster, but relies on the kernel you have, so it is much > more complicated to be included in software parts. > It is mostly needed only for very high speed applications > > PREEMPT-RT is a a little bit slower than RTAI, but can be implemented in > software much easier, just imagine it is a modul. > > That is very simple explained, there are more differences. For a normal > CNC opperation both should work fine. But if you use i.e. software > stepgenerator over a LPT, than take the RTAI. > > Norbert Depending on the hardware the differences between RTAI and Preempt-RT may be minimal: http://freeby.mesanet.com/g3258-rtai.png http://freeby.mesanet.com/h97-g3258-preemt-rt.png Both about 1/2 a day of YouTube videos (I favor the crackling fireplace ones) and 10 glxgears each I'll try some Skylake hardware when I can figure out how to build the latest (4.4-rc6-rt1) Preempt-RT kernel Note that both the latency test and latency histogram mainly display _dispatch_ latency. Actual latency to _do_ anything (allocate memory, do I/O, access the PCI bus, etc) will be significantly worse Peter Wallace Mesa Electronics -- ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
