Hello all, I am writing a config for a multi-socket system in gem5 to use in testing a research design implementation. I am modifying x86_board.py, abstract_system_board.py, and abstract_board.py. I want to modify the X86Board class to accept a list of processors instead of a single processor, and set up a multiprocessor system. In AbstractSystemBoard and AbstractBoard, the modifications seem to be as simple as adding a few loops to code relevant to the processor(s) However, in x86_board.py, in the X86Board class, there is the function _setup_io_devices(), which creates a set of objects that the code comments say relate to Intel MP. From what I can tell, IntelMP refers to the Intel MultiProcessor standard, and primarily relates to interrupt controllers. How would I need to modify this function, and other code related to Intel MP to properly support multiple processors? Thank you, -James Pangia

Hey James, \ Perhaps I am very wrong in my assumptions here, but is there any difference in your idea between a "multiprocessor" setup and a multicore setup? In the gem5 stdlib design each board has one processor, but each processor can have as many CPUs/Cores as you desire. I don't know the ins and outs of your research here, but do you really want to simulate separate processors or just have a system with many cores? The code you see in \`_setup_io_devices()\` sets up an \`X86IntelMPProcessor\` for each core in the processor and is our way of conforming to this standard (-ish... I think...). Behind the scenes all a gem5 standard library "processor" is, is a list of Cores in which the processor object manages. While we could have more than one processor per-board I don't know how it would actually change what's being simulated. I think you could have more than one "processor" per board but I think the way of handling them in a simulation would be to essentially to create a union of all the cores across all the processors and, effectively, treat them as one big processor anyway. Again, perhaps I've completely misunderstood this idea, but I'd suggest looking at gem5 standard library processors and how they are constructed and used inside a simulation and see if you can make extensions/modifications there first: <https://github.com/gem5/gem5/tree/stable/src/python/gem5/components/processors>. Kind regards, Bobby

Thanks for the reply, Bobby My research does require multiple separate processors/sockets, not just many cores. I explored using multiple Processor objects a little further, but the necessary modifications proved too complicated to spend more time exploring. Instead, I will be faking multiple sockets by tracking which core a request came from and modifying the MemCtrl class to add a different memory access latency depending on where the target physical address is—effectively, I’m faking NUMA. This choice also makes sense in light of your comment that the Core objects all wind up in one pool from the simulator’s perspective anyway, so thank you for that clarification. On Wed, Oct 11, 2023 at 5:09 PM bbruce--- via gem5-users < gem5-users@gem5.org> wrote: > Hey James, > > > Perhaps I am very wrong in my assumptions here, but is there any > difference in your idea between a "multiprocessor" setup and a multicore > setup? In the gem5 stdlib design each board has one processor, but each > processor can have as many CPUs/Cores as you desire. I don't know the ins > and outs of your research here, but do you really want to simulate separate > processors or just have a system with many cores? The code you see in > `_setup_io_devices()` sets up an `X86IntelMPProcessor` for each core in the > processor and is our way of conforming to this standard (-ish... I > think...). > > > Behind the scenes all a gem5 standard library "processor" is, is a list of > Cores in which the processor object manages. While we could have more than > one processor per-board I don't know how it would actually change what's > being simulated. > > > I think you could have more than one "processor" per board but I think the > way of handling them in a simulation would be to essentially to create a > union of all the cores across all the processors and, effectively, treat > them as one big processor anyway. > > > Again, perhaps I've completely misunderstood this idea, but I'd suggest > looking at gem5 standard library processors and how they are constructed > and used inside a simulation and see if you can make > extensions/modifications there first: > https://github.com/gem5/gem5/tree/stable/src/python/gem5/components/processors > . > > > Kind regards, > > Bobby > _______________________________________________ > gem5-users mailing list -- gem5-users@gem5.org > To unsubscribe send an email to gem5-users-leave@gem5.org >