From 2ee04d65873bac7a91d9d309eff79d13b8cc8103 Mon Sep 17 00:00:00 2001
From: Derek Hower <drh5@cs.wisc.edu>
Date: Fri, 13 Nov 2009 09:43:39 -0600
Subject: ruby: reduce the memory usage of ruby by making memory vector page
 based

---
 src/mem/ruby/system/MemoryVector.hh | 72 +++++++++++++++++++++++++++++--------
 1 file changed, 58 insertions(+), 14 deletions(-)

diff --git a/src/mem/ruby/system/MemoryVector.hh b/src/mem/ruby/system/MemoryVector.hh
index c5f3cea7f..775244840 100644
--- a/src/mem/ruby/system/MemoryVector.hh
+++ b/src/mem/ruby/system/MemoryVector.hh
@@ -21,61 +21,105 @@ class MemoryVector {
   void write(const Address & paddr, uint8* data, int len);
   uint8* read(const Address & paddr, uint8* data, int len);
 
- private:
-  uint8* getBlockPtr(const Address & paddr);
+private:
+  uint8* getBlockPtr(const PhysAddress & addr);
 
   uint32 m_size;
-  uint8* m_vec;
+  uint8** m_pages;
+  uint32 m_num_pages;
+  const uint32 m_page_offset_mask;
 };
 
 inline
 MemoryVector::MemoryVector()
+  : m_page_offset_mask(4095)
 {
   m_size = 0;
-  m_vec = NULL;
+  m_num_pages = 0;
+  m_pages = NULL;
 }
 
 inline
 MemoryVector::MemoryVector(uint32 size)
+  : m_page_offset_mask(4095)
 {
-  m_size = size;
-  m_vec = new uint8[size];
+  setSize(size);
 }
 
 inline
 MemoryVector::~MemoryVector()
 {
-  delete [] m_vec;
+  for (int i=0; i<m_num_pages; i++) {
+    if (m_pages[i] != 0) {
+      delete [] m_pages[i];
+    }
+  }
+  delete [] m_pages;
 }
 
 inline
 void MemoryVector::setSize(uint32 size)
 {
+  if (m_pages != NULL){
+    for (int i=0; i<m_num_pages; i++) {
+      if (m_pages[i] != 0) {
+        delete [] m_pages[i];
+      }
+    }
+    delete [] m_pages;
+  }
   m_size = size;
-  if (m_vec != NULL)
-    delete [] m_vec;
-  m_vec = new uint8[size];
+  assert(size%4096 == 0);
+  m_num_pages = size >> 12;
+  m_pages = new uint8*[m_num_pages];
+  memset(m_pages, 0, m_num_pages * sizeof(uint8*));
 }
 
 inline
 void MemoryVector::write(const Address & paddr, uint8* data, int len)
 {
   assert(paddr.getAddress() + len <= m_size);
-  memcpy(m_vec + paddr.getAddress(), data, len);
+  uint32 page_num = paddr.getAddress() >> 12;
+  if (m_pages[page_num] == 0) {
+    bool all_zeros = true;
+    for (int i=0;i<len;i++) {
+      if (data[i] != 0) {
+        all_zeros = false;
+        break;
+      }
+    }
+    if (all_zeros) return;
+    m_pages[page_num] = new uint8[4096];
+    memset(m_pages[page_num], 0, 4096);
+    uint32 offset = paddr.getAddress() & m_page_offset_mask;
+    memcpy(&m_pages[page_num][offset], data, len);
+  } else {
+    memcpy(&m_pages[page_num][paddr.getAddress()&m_page_offset_mask], data, len);
+  }
 }
 
 inline
 uint8* MemoryVector::read(const Address & paddr, uint8* data, int len)
 {
   assert(paddr.getAddress() + len <= m_size);
-  memcpy(data, m_vec + paddr.getAddress(), len);
+  uint32 page_num = paddr.getAddress() >> 12;
+  if (m_pages[page_num] == 0) {
+    memset(data, 0, len);
+  } else {
+    memcpy(data, &m_pages[page_num][paddr.getAddress()&m_page_offset_mask], len);
+  }
   return data;
 }
 
 inline
-uint8* MemoryVector::getBlockPtr(const Address & paddr)
+uint8* MemoryVector::getBlockPtr(const PhysAddress & paddr)
 {
-  return m_vec + paddr.getAddress();
+  uint32 page_num = paddr.getAddress() >> 12;
+  if (m_pages[page_num] == 0) {
+    m_pages[page_num] = new uint8[4096];
+    memset(m_pages[page_num], 0, 4096);
+  }
+  return &m_pages[page_num][paddr.getAddress()&m_page_offset_mask];
 }
 
 #endif // MEMORYVECTOR_H
-- 
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