Re: [Emc-users] Raspberry Pi PREEMPT-RT

[Peter C. W. <pc...@me...>]

On Fri, 22 Jun 2018, John Dammeyer wrote:

> Date: Fri, 22 Jun 2018 08:39:55 -0700
> From: John Dammeyer <jo...@au...>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <emc...@li...>
> To: "'Enhanced Machine Controller (EMC)'" <emc...@li...>
> Subject: Re: [Emc-users] Raspberry Pi PREEMPT-RT
> 
> I believe the BeagleBone Black MachineKit uses one of the RT kernel 
> modifications.  However, it's the two PRU processors inside the Beagle that 
> make it possible to run stepping motors and decode encoders.
>
>It actually boggles my mind that decades after say OS-968K, VRTX-86 RTOS or 
>for that matter the RTOS I wrote in University that something like Linux 
>doesnÿÿt have a RT Kernal and that if you didnÿÿt want RT capability that 
>then 
>you'd have flavours off the main line for that.
>
>Perhaps so much of the internal Linux code would be broken with badly written 
>code that has priority inversions etc. and would therefore be broken that it 
>continues down the path of non-real time.
>
>Simply mind boggling.
>
>John



Linux has had real time kernels for more than 10 years
Currently Preempt-RT patches track mainline Linux kernels and are no more than 
a version or so behind mainline

There are good reasons for using not real time kernels unless real time is 
required (many real time kernel patches trade off throughput for better 
latency)

Peter Wallace
Mesa Electronics