cpu: Add request elasticity to the traffic generator

This patch adds an optional request elasticity to the traffic
generator, effectievly compensating for it in the case of the linear
and random generators, and adding it in the case of the trace
generator. The accounting is left with the top-level traffic
generator, and the individual generators do the necessary math as part
of determining the next packet tick.

Note that in the linear and random generators we have to compensate
for the blocked time to not be elastic, i.e. without this patch the
aforementioned generators will slow down in the case of back-pressure.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/cpu/testers/traffic_gen/TrafficGen.py b/src/cpu/testers/traffic_gen/TrafficGen.py
index 916279f91..f29cedb3a 100644
--- a/src/cpu/testers/traffic_gen/TrafficGen.py
+++ b/src/cpu/testers/traffic_gen/TrafficGen.py
@@ -71,3 +71,9 @@ class TrafficGen(MemObject):
 
     # System used to determine the mode of the memory system
     system = Param.System(Parent.any, "System this generator is part of")
+
+    # Should requests respond to back-pressure or not, if true, the
+    # rate of the traffic generator will be slowed down if requests
+    # are not immediately accepted
+    elastic_req = Param.Bool(False,
+                             "Slow down requests in case of backpressure")