diff -r 85ac67b53235 -r c64bbbe67e13 src/mem/XBar.py
--- a/src/mem/XBar.py	Fri Aug 21 16:47:48 2015 +0100
+++ b/src/mem/XBar.py	Fri Aug 21 16:47:57 2015 +0100
@@ -112,6 +112,9 @@
 
     system = Param.System(Parent.any, "System that the crossbar belongs to.")
 
+    # Sanity check on max capacity to track, adjust if needed.
+    max_capacity = Param.MemorySize('16MB', "Maximum capacity of snoop filter")
+
 # We use a coherent crossbar to connect multiple masters to the L2
 # caches. Normally this crossbar would be part of the cache itself.
 class L2XBar(CoherentXBar):
@@ -125,6 +128,11 @@
     response_latency = 1
     snoop_response_latency = 1
 
+    # Use a snoop-filter by default, and set the latency to zero as
+    # the lookup is assumed to overlap with the frontend latency of
+    # the crossbar
+    snoop_filter = SnoopFilter(lookup_latency = 0)
+
 # One of the key coherent crossbar instances is the system
 # interconnect, tying together the CPU clusters, GPUs, and any I/O
 # coherent masters, and DRAM controllers.
diff -r 85ac67b53235 -r c64bbbe67e13 src/mem/snoop_filter.hh
--- a/src/mem/snoop_filter.hh	Fri Aug 21 16:47:48 2015 +0100
+++ b/src/mem/snoop_filter.hh	Fri Aug 21 16:47:57 2015 +0100
@@ -90,7 +90,8 @@
 
     SnoopFilter (const SnoopFilterParams *p) :
         SimObject(p), reqLookupResult(cachedLocations.end()), retryItem{0, 0},
-        linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency)
+        linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency),
+        maxEntryCount(p->max_capacity / p->system->cacheLineSize())
     {
     }
 
@@ -254,6 +255,8 @@
     const unsigned linesize;
     /** Latency for doing a lookup in the filter */
     const Cycles lookupLatency;
+    /** Max capacity in terms of cache blocks tracked, for sanity checking */
+    const unsigned maxEntryCount;
 
     /** Statistics */
     Stats::Scalar totRequests;
diff -r 85ac67b53235 -r c64bbbe67e13 src/mem/snoop_filter.cc
--- a/src/mem/snoop_filter.cc	Fri Aug 21 16:47:48 2015 +0100
+++ b/src/mem/snoop_filter.cc	Fri Aug 21 16:47:57 2015 +0100
@@ -184,6 +184,10 @@
     auto sf_it = cachedLocations.find(line_addr);
     bool is_hit = (sf_it != cachedLocations.end());
 
+    panic_if(!is_hit && (cachedLocations.size() >= maxEntryCount),
+             "snoop filter exceeded capacity of %d cache blocks\n",
+             maxEntryCount);
+
     // If the snoop filter has no entry and its an uncacheable
     // request, do not create a new snoop filter entry, simply return
     // a NULL portlist.