gem5/src/mem/ruby/network/garnet2.0/SwitchAllocator.cc
Tushar Krishna dbe8892b76 ruby: garnet2.0
Revamped version of garnet with more optimized single-cycle routers,
more configurability, and cleaner code.
2016-10-06 14:35:22 -04:00

389 lines
13 KiB
C++

/*
* Copyright (c) 2008 Princeton University
* Copyright (c) 2016 Georgia Institute of Technology
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Niket Agarwal
* Tushar Krishna
*/
#include "mem/ruby/network/garnet2.0/SwitchAllocator.hh"
#include "debug/RubyNetwork.hh"
#include "mem/ruby/network/garnet2.0/GarnetNetwork.hh"
#include "mem/ruby/network/garnet2.0/InputUnit.hh"
#include "mem/ruby/network/garnet2.0/OutputUnit.hh"
#include "mem/ruby/network/garnet2.0/Router.hh"
SwitchAllocator::SwitchAllocator(Router *router)
: Consumer(router)
{
m_router = router;
m_num_vcs = m_router->get_num_vcs();
m_vc_per_vnet = m_router->get_vc_per_vnet();
m_input_arbiter_activity = 0;
m_output_arbiter_activity = 0;
}
void
SwitchAllocator::init()
{
m_input_unit = m_router->get_inputUnit_ref();
m_output_unit = m_router->get_outputUnit_ref();
m_num_inports = m_router->get_num_inports();
m_num_outports = m_router->get_num_outports();
m_round_robin_inport.resize(m_num_outports);
m_round_robin_invc.resize(m_num_inports);
m_port_requests.resize(m_num_outports);
m_vc_winners.resize(m_num_outports);
for (int i = 0; i < m_num_inports; i++) {
m_round_robin_invc[i] = 0;
}
for (int i = 0; i < m_num_outports; i++) {
m_port_requests[i].resize(m_num_inports);
m_vc_winners[i].resize(m_num_inports);
m_round_robin_inport[i] = 0;
for (int j = 0; j < m_num_inports; j++) {
m_port_requests[i][j] = false; // [outport][inport]
}
}
}
/*
* The wakeup function of the SwitchAllocator performs a 2-stage
* seperable switch allocation. At the end of the 2nd stage, a free
* output VC is assigned to the winning flits of each output port.
* There is no separate VCAllocator stage like the one in garnet1.0.
* At the end of this function, the router is rescheduled to wakeup
* next cycle for peforming SA for any flits ready next cycle.
*/
void
SwitchAllocator::wakeup()
{
arbitrate_inports(); // First stage of allocation
arbitrate_outports(); // Second stage of allocation
clear_request_vector();
check_for_wakeup();
}
/*
* SA-I (or SA-i) loops through all input VCs at every input port,
* and selects one in a round robin manner.
* - For HEAD/HEAD_TAIL flits only selects an input VC whose output port
* has at least one free output VC.
* - For BODY/TAIL flits, only selects an input VC that has credits
* in its output VC.
* Places a request for the output port from this input VC.
*/
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];
// Select next round robin vc candidate within valid vnet
int next_round_robin_invc = invc;
next_round_robin_invc++;
if (next_round_robin_invc >= m_num_vcs)
next_round_robin_invc = 0;
m_round_robin_invc[inport] = next_round_robin_invc;
for (int invc_iter = 0; invc_iter < m_num_vcs; invc_iter++) {
if (m_input_unit[inport]->need_stage(invc, SA_,
m_router->curCycle())) {
// This flit is in SA stage
int outport = m_input_unit[inport]->get_outport(invc);
int outvc = m_input_unit[inport]->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[outport][inport] = true;
m_vc_winners[outport][inport]= invc;
break; // got one vc winner for this port
}
}
invc++;
if (invc >= m_num_vcs)
invc = 0;
}
}
}
/*
* SA-II (or SA-o) loops through all output ports,
* and selects one input VC (that placed a request during SA-I)
* as the winner for this output port in a round robin manner.
* - For HEAD/HEAD_TAIL flits, performs simplified outvc allocation.
* (i.e., select a free VC from the output port).
* - For BODY/TAIL flits, decrement a credit in the output vc.
* The winning flit is read out from the input VC and sent to the
* CrossbarSwitch.
* An increment_credit signal is sent from the InputUnit
* to the upstream router. For HEAD_TAIL/TAIL flits, is_free_signal in the
* credit is set to true.
*/
void
SwitchAllocator::arbitrate_outports()
{
// Now there are a set of input vc requests for output vcs.
// Again do round robin arbitration on these requests
// Independent arbiter at each output port
for (int outport = 0; outport < m_num_outports; outport++) {
int inport = m_round_robin_inport[outport];
m_round_robin_inport[outport]++;
if (m_round_robin_inport[outport] >= m_num_inports)
m_round_robin_inport[outport] = 0;
for (int inport_iter = 0; inport_iter < m_num_inports;
inport_iter++) {
// inport has a request this cycle for outport
if (m_port_requests[outport][inport]) {
// grant this outport to this inport
int invc = m_vc_winners[outport][inport];
int outvc = m_input_unit[inport]->get_outvc(invc);
if (outvc == -1) {
// VC Allocation - select any free VC from outport
outvc = vc_allocate(outport, inport, invc);
}
// remove flit from Input VC
flit *t_flit = m_input_unit[inport]->getTopFlit(invc);
DPRINTF(RubyNetwork, "SwitchAllocator at Router %d "
"granted outvc %d at outport %d "
"to invc %d at inport %d to flit %s at "
"time: %lld\n",
m_router->get_id(), outvc,
m_router->getPortDirectionName(
m_output_unit[outport]->get_direction()),
invc,
m_router->getPortDirectionName(
m_input_unit[inport]->get_direction()),
*t_flit,
m_router->curCycle());
// Update outport field in the flit since this is
// used by CrossbarSwitch code to send it out of
// correct outport.
// Note: post route compute in InputUnit,
// outport is updated in VC, but not in flit
t_flit->set_outport(outport);
// set outvc (i.e., invc for next hop) in flit
// (This was updated in VC by vc_allocate, but not in flit)
t_flit->set_vc(outvc);
// decrement credit in outvc
m_output_unit[outport]->decrement_credit(outvc);
// flit ready for Switch Traversal
t_flit->advance_stage(ST_, m_router->curCycle());
m_router->grant_switch(inport, t_flit);
m_output_arbiter_activity++;
if ((t_flit->get_type() == TAIL_) ||
t_flit->get_type() == HEAD_TAIL_) {
// This Input VC should now be empty
assert(!(m_input_unit[inport]->isReady(invc,
m_router->curCycle())));
// Free this VC
m_input_unit[inport]->set_vc_idle(invc,
m_router->curCycle());
// Send a credit back
// along with the information that this VC is now idle
m_input_unit[inport]->increment_credit(invc, true,
m_router->curCycle());
} else {
// Send a credit back
// but do not indicate that the VC is idle
m_input_unit[inport]->increment_credit(invc, false,
m_router->curCycle());
}
// remove this request
m_port_requests[outport][inport] = false;
break; // got a input winner for this outport
}
inport++;
if (inport >= m_num_inports)
inport = 0;
}
}
}
/*
* A flit can be sent only if
* (1) there is at least one free output VC at the
* output port (for HEAD/HEAD_TAIL),
* or
* (2) if there is at least one credit (i.e., buffer slot)
* within the VC for BODY/TAIL flits of multi-flit packets.
* and
* (3) pt-to-pt ordering is not violated in ordered vnets, i.e.,
* there should be no other flit in this input port
* within an ordered vnet
* that arrived before this flit and is requesting the same output port.
*/
bool
SwitchAllocator::send_allowed(int inport, int invc, int outport, int outvc)
{
// Check if outvc needed
// Check if credit needed (for multi-flit packet)
// Check if ordering violated (in ordered vnet)
int vnet = get_vnet(invc);
bool has_outvc = (outvc != -1);
bool has_credit = false;
if (!has_outvc) {
// needs outvc
// this is only true for HEAD and HEAD_TAIL flits.
if (m_output_unit[outport]->has_free_vc(vnet)) {
has_outvc = true;
// each VC has at least one buffer,
// so no need for additional credit check
has_credit = true;
}
} else {
has_credit = m_output_unit[outport]->has_credit(outvc);
}
// cannot send if no outvc or no credit.
if (!has_outvc || !has_credit)
return false;
// protocol ordering check
if ((m_router->get_net_ptr())->isVNetOrdered(vnet)) {
// enqueue time of this flit
Cycles t_enqueue_time = m_input_unit[inport]->get_enqueue_time(invc);
// check if any other flit is ready for SA and for same output port
// and was enqueued before this flit
int vc_base = vnet*m_vc_per_vnet;
for (int vc_offset = 0; vc_offset < m_vc_per_vnet; vc_offset++) {
int temp_vc = vc_base + vc_offset;
if (m_input_unit[inport]->need_stage(temp_vc, SA_,
m_router->curCycle()) &&
(m_input_unit[inport]->get_outport(temp_vc) == outport) &&
(m_input_unit[inport]->get_enqueue_time(temp_vc) <
t_enqueue_time)) {
return false;
}
}
}
return true;
}
// Assign a free VC to the winner of the output port.
int
SwitchAllocator::vc_allocate(int outport, int inport, int invc)
{
// Select a free VC from the output port
int outvc = m_output_unit[outport]->select_free_vc(get_vnet(invc));
// has to get a valid VC since it checked before performing SA
assert(outvc != -1);
m_input_unit[inport]->grant_outvc(invc, outvc);
return outvc;
}
// Wakeup the router next cycle to perform SA again
// if there are flits ready.
void
SwitchAllocator::check_for_wakeup()
{
Cycles nextCycle = m_router->curCycle() + Cycles(1);
for (int i = 0; i < m_num_inports; i++) {
for (int j = 0; j < m_num_vcs; j++) {
if (m_input_unit[i]->need_stage(j, SA_, nextCycle)) {
m_router->schedule_wakeup(Cycles(1));
return;
}
}
}
}
int
SwitchAllocator::get_vnet(int invc)
{
int vnet = invc/m_vc_per_vnet;
assert(vnet < m_router->get_num_vnets());
return vnet;
}
// Clear the request vector within the allocator at end of SA-II.
// Was populated by SA-I.
void
SwitchAllocator::clear_request_vector()
{
for (int i = 0; i < m_num_outports; i++) {
for (int j = 0; j < m_num_inports; j++) {
m_port_requests[i][j] = false;
}
}
}