changeset 3c38d3e74980 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=3c38d3e74980
description:
ruby: fix round robin arbiter in garnet2.0
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.
diffstat:
src/mem/ruby/network/garnet2.0/SwitchAllocator.cc | 22 +++++++++++-----------
1 files changed, 11 insertions(+), 11 deletions(-)
diffs (53 lines):
diff -r 79c3f6a60392 -r 3c38d3e74980
src/mem/ruby/network/garnet2.0/SwitchAllocator.cc
--- a/src/mem/ruby/network/garnet2.0/SwitchAllocator.cc Sat Feb 11 11:11:48
2017 -0500
+++ b/src/mem/ruby/network/garnet2.0/SwitchAllocator.cc Sun Feb 12 15:00:03
2017 -0500
@@ -116,13 +116,6 @@
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 @@
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 @@
// 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 @@
// 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
}
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