Re: [Emc-users] multiple instances of emc?

[Rafael S. <ra...@li...>]

On 03/31/2011 11:05 AM, Viesturs Lācis wrote:
> 2011/3/31 Rafael Skodlar<ra...@li...>:
>>
>> However, we still haven't addressed the original question about running
>> multiple instances of EMC2 on the same hardware. Two options are
>> possible here IMO:
>> - expand EMC2 in such a way to present itself as running another
>> instance of itself on different CPU core(s) virtually like a thread,
>> - or run independent instances of EMC in VMs in different CPU core(s)
>> and selected set of peripherals.
>>
>
> Something similar has been discussed previously. I found one good
> quote from Andy:
>
> 2010/12/13 andy pugh<bod...@gm...>:.
>>
>> The other alternative would be to write a new interpreter.
>>
>
> I think that this suggestion would work here too, because it was
> mentioned that running EMC on a virtual machine will have enormous
> jitter. With all due respect to members of EMC community, I doubt that
> we can fix that, so I think that Your second suggestion on
> virtualization is denied.

Denial can only relate to current state of the (EMC) art. I simply 
listed an option that has been implemented in commercial embedded 
systems software.

VM running on a dedicated CPU core independently under RT micro kernel:
http://www.enea.com/Templates/Product____27035.aspx

http://industrial-embedded.com/virtualization-platforms-real-time-embedded-systems

Under Application examples: "the manufacturer can run the legacy 
real-time software on one core in a multicore processor and implement 
the new user interface functionality on the remaining cores. The VMM in 
this case partitions the processor‚ I/O, memory, and other resources to 
ensure that only the machine control software has direct access to the 
motion control hardware and that it operates on a dedicated CPU core. 
This creates a separation between the real-time OS and the user 
interface software, avoiding interference between the two OSs and 
thereby protecting the timing loops the legacy real-time software 
manages from being violated by operations the new human interface 
software performs."

Today's motherboards come with multi core CPUs and it's a shame we 
cannot use one or more cores for EMC under tight RT constraints and GUI 
part of application in another one.

> I think that instead of trying to reinvent the wheel and run several
> instances of EMC on a single PC and getting into trouble of
> synchronizing them, I think that investigating the option of expanding
> current capabilities of interpreter and adding few more axes might be
> easier.

Agree. This is the interim solution.

> As Andy mentioned, joints_axes_3 branch already should allow for a
> total number of joints to exceed 9.
>
> Viesturs

--
Rafael