ruby: patch checkpoint restore with garnet

Due to recent changes to clocking system in Ruby and the way Ruby restores
state from a checkpoint, garnet was failing to run from a checkpointed state.
The problem is that Ruby resets the time to zero while warming up the caches.
If any component records a local copy of the time (read calls curCycle())
before the simulation has started, then that component will not operate until
that time is reached. In the context of this particular patch, the Garnet
Network class calls curCycle() at multiple places. Any non-operational
component can block in requests in the memory system, which the system
interprets as a deadlock. This patch makes changes so that Garnet can
successfully run from checkpointed state.

It adds a globally visible time at which the actual execution started. This
time is initialized in RubySystem::startup() function. This variable is only
meant for components with in Ruby. This replaces the private variable that
was maintained within Garnet since it is not possible to figure out the
correct time when the value of this variable can be set.

The patch also does away with all cases where curCycle() is called with in
some Ruby component before the system has actually started executing. This
is required due to the quirky manner in which ruby restores from a checkpoint.

7 files changed, 10 insertions, 13 deletions

diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
index c4965af17..4b1e0d0d7 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
@@ -270,7 +270,7 @@ GarnetNetwork_d::printLinkStats(ostream& out) const
     for (int i = 0; i < m_link_ptr_vector.size(); i++) {
         average_link_utilization +=
             (double(m_link_ptr_vector[i]->getLinkUtilization())) /
-            (double(curCycle() - m_ruby_start));
+            (double(curCycle() - g_ruby_start));
 
         vector<int> vc_load = m_link_ptr_vector[i]->getVcLoad();
         for (int j = 0; j < vc_load.size(); j++) {
@@ -289,7 +289,7 @@ GarnetNetwork_d::printLinkStats(ostream& out) const
             continue;
 
         average_vc_load[i] = (double(average_vc_load[i])) /
-            (double(curCycle() - m_ruby_start));
+            (double(curCycle() - g_ruby_start));
         out << "Average VC Load [" << i << "] = " << average_vc_load[i]
             << " flits/cycle " << endl;
     }
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/InputUnit_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/InputUnit_d.cc
index 7db9db56b..82d89912e 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/InputUnit_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/InputUnit_d.cc
@@ -53,7 +53,7 @@ InputUnit_d::InputUnit_d(int id, Router_d *router) : Consumer(router)
     // Instantiating the virtual channels
     m_vcs.resize(m_num_vcs);
     for (int i=0; i < m_num_vcs; i++) {
-        m_vcs[i] = new VirtualChannel_d(i, m_router->curCycle());
+        m_vcs[i] = new VirtualChannel_d(i);
     }
 }
 
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc
index e49216476..adf1c1a4d 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc
@@ -71,7 +71,6 @@ NetworkInterface_d::NetworkInterface_d(int id, int virtual_networks,
 
     for (int i = 0; i < m_num_vcs; i++) {
         m_out_vc_state.push_back(new OutVcState_d(i, m_net_ptr));
-        m_out_vc_state[i]->setState(IDLE_, m_net_ptr->curCycle());
     }
 }
 
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.cc
index d006591c0..a11bf0c2d 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.cc
@@ -33,16 +33,15 @@
 #include "mem/ruby/system/System.hh"
 
 OutVcState_d::OutVcState_d(int id, GarnetNetwork_d *network_ptr)
+    : m_time(0)
 {
-    m_network_ptr = network_ptr;
     m_id = id;
     m_vc_state = IDLE_;
-    m_time = m_network_ptr->curCycle();
 
-    if (m_network_ptr->get_vnet_type(id) == DATA_VNET_)
-        m_credit_count = m_network_ptr->getBuffersPerDataVC();
+    if (network_ptr->get_vnet_type(id) == DATA_VNET_)
+        m_credit_count = network_ptr->getBuffersPerDataVC();
     else
-        m_credit_count = m_network_ptr->getBuffersPerCtrlVC();
+        m_credit_count = network_ptr->getBuffersPerCtrlVC();
 
     assert(m_credit_count >= 1);
 }
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.hh b/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.hh
index 07b197cf5..08ceecec0 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.hh
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/OutVcState_d.hh
@@ -61,7 +61,6 @@ class OutVcState_d
     inline void decrement_credit()  { m_credit_count--; }
 
   private:
-    GarnetNetwork_d *m_network_ptr;
     int m_id ;
     Cycles m_time;
     VC_state_type m_vc_state;
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.cc
index bfeecbc25..510a79e8d 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.cc
@@ -30,13 +30,13 @@
 
 #include "mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.hh"
 
-VirtualChannel_d::VirtualChannel_d(int id, Cycles curTime)
+VirtualChannel_d::VirtualChannel_d(int id)
     : m_enqueue_time(INFINITE_)
 {
     m_id = id;
     m_input_buffer = new flitBuffer_d();
     m_vc_state.first = IDLE_;
-    m_vc_state.second = curTime;
+    m_vc_state.second = Cycles(0);
 }
 
 VirtualChannel_d::~VirtualChannel_d()
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.hh b/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.hh
index 9e8b95d9d..d19630305 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.hh
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/VirtualChannel_d.hh
@@ -39,7 +39,7 @@
 class VirtualChannel_d
 {
   public:
-    VirtualChannel_d(int id, Cycles curTime);
+    VirtualChannel_d(int id);
     ~VirtualChannel_d();
 
     bool need_stage(VC_state_type state, flit_stage stage, Cycles curTime);