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ruby: fix round robin arbiter in garnet2.0

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The rr arbiter pointer in garnet was getting updated on every request,
even if there is no grant. This was leading to a huge variance in wait
time at a router at high injection rates.
This patch corrects it to update upon a grant.
This commit is contained in:
Tushar Krishna 2017-02-12 15:00:03 -05:00
parent f3643c8a60
commit 1be05afa06
1 changed files with 11 additions and 11 deletions
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22
src/mem/ruby/network/garnet2.0/SwitchAllocator.cc
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@ -116,13 +116,6 @@ SwitchAllocator::arbitrate_inports()
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_,
@ -142,6 +135,12 @@ SwitchAllocator::arbitrate_inports()
m_input_arbiter_activity++;
m_port_requests[outport][inport] = true;
m_vc_winners[outport][inport]= invc;
// Update Round Robin pointer
m_round_robin_invc[inport]++;
if (m_round_robin_invc[inport] >= m_num_vcs)
m_round_robin_invc[inport] = 0;
break; // got one vc winner for this port
}
}
@ -175,10 +174,6 @@ SwitchAllocator::arbitrate_outports()
// 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++) {
@ -256,6 +251,11 @@ SwitchAllocator::arbitrate_outports()
// remove this request
m_port_requests[outport][inport] = false;
// Update Round Robin pointer
m_round_robin_inport[outport]++;
if (m_round_robin_inport[outport] >= m_num_inports)
m_round_robin_inport[outport] = 0;
break; // got a input winner for this outport
}