Garnet code flow

[olumide-x]

Hello,

gem5 newbie here.

I'm reading the gem5 source and I find line 119 of SwitchAllocator.cc confusing. Why call m_router->getInputUnit(inport) in the inner loop even though inport does not appear to have changed?

void
SwitchAllocator::arbitrate_inports()
{
    // Select a VC from each input in a round robin manner
    // Independent arbiter at each input port
    for (int inport = 0; inport < m_num_inports; inport++) {
        int invc = m_round_robin_invc[inport];

        for (int invc_iter = 0; invc_iter < m_num_vcs; invc_iter++) {
            auto input_unit = m_router->getInputUnit(inport);  // <----- MY QUESTION IS ABOUT THIS LINE

            if (input_unit->need_stage(invc, SA_, curTick())) {
                // This flit is in SA stage

                int outport = input_unit->get_outport(invc);
                int outvc = input_unit->get_outvc(invc);

                // check if the flit in this InputVC is allowed to be sent
                // send_allowed conditions described in that function.
                bool make_request =
                    send_allowed(inport, invc, outport, outvc);

                if (make_request) {
                    m_input_arbiter_activity++;
                    m_port_requests[inport] = outport;
                    m_vc_winners[inport] = invc;

                    break; // got one vc winner for this port
                }
            }

            invc++;
            if (invc >= m_num_vcs)
                invc = 0;
        }
    }
}

Also, I find the first line of the code flow difficult to parse.

CODE FLOW
- NetworkInterface.cc::wakeup()
    * Every NI connected to one coherence protocol controller on one end, and one router on the other.

Does this mean that every NI is by definition "connected to one coherence protocol controller on one end, and one router on the other", or do the following steps apply only to NIs that are "connected to one coherence protocol controller on one end, and one router on the other"?

[olumide-x]

This question has been answered on the gem5-dev forum.