mem: Avoid explicitly zeroing the memory backing store

This patch removes the explicit memset as it is redundant and causes
the simulator to touch the entire space, forcing the host system to
allocate the pages.

Anonymous pages are mapped on the first access, and the page-fault
handler is responsible for zeroing them. Thus, the pages are still
zeroed, but we avoid touching the entire allocated space which enables
us to use much larger memory sizes as long as not all the memory is
actually used.

1 files changed, 0 insertions, 17 deletions

diff --git a/src/mem/physical.cc b/src/mem/physical.cc
index 4b7001eb5..10176bba0 100644
--- a/src/mem/physical.cc
+++ b/src/mem/physical.cc
@@ -162,10 +162,6 @@ PhysicalMemory::createBackingStore(AddrRange range,
     // it appropriately
     backingStore.push_back(make_pair(range, pmem));
 
-    // count how many of the memories are to be zero initialized so we
-    // can see if some but not all have this parameter set
-    uint32_t init_to_zero = 0;
-
     // point the memories to their backing store, and if requested,
     // initialize the memory range to 0
     for (vector<AbstractMemory*>::const_iterator m = _memories.begin();
@@ -173,19 +169,6 @@ PhysicalMemory::createBackingStore(AddrRange range,
         DPRINTF(BusAddrRanges, "Mapping memory %s to backing store\n",
                 (*m)->name());
         (*m)->setBackingStore(pmem);
-
-        // if it should be zero, then go and make it so
-        if ((*m)->initToZero()) {
-            ++init_to_zero;
-        }
-    }
-
-    if (init_to_zero != 0) {
-        if (init_to_zero != _memories.size())
-            fatal("Some, but not all memories in range %s are set zero\n",
-                  range.to_string());
-
-        memset(pmem, 0, range.size());
     }
 }