[mc] Bring back soft-dirty tracking from the dead 💀

[simgrid.git] / src / mc / mc_page_snapshot.cpp

diff --git a/src/mc/mc_page_snapshot.cpp b/src/mc/mc_page_snapshot.cpp
index 2efe58b..b180c40 100644 (file)
--- a/src/mc/mc_page_snapshot.cpp
+++ b/src/mc/mc_page_snapshot.cpp
@@ -15,6 +15,9 @@
 
 #include <xbt/mmalloc.h>
 
+#define SOFT_DIRTY_BIT_NUMBER 55
+#define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
+
 using simgrid::mc::remote;
 
 namespace simgrid {
@@ -27,7 +30,8 @@ namespace mc {
  *  @return                Snapshot page numbers of this new snapshot
  */
 PerPageCopy::PerPageCopy(PageStore& store, AddressSpace& as,
-    remote_ptr<void> addr, std::size_t page_count)
+    remote_ptr<void> addr, std::size_t page_count,
+    const size_t* ref_page_numbers, const std::uint64_t* pagemap)
 {
   store_ = &store;
   this->pagenos_.resize(page_count);
@@ -35,6 +39,13 @@ PerPageCopy::PerPageCopy(PageStore& store, AddressSpace& as,
 
   for (size_t i = 0; i != page_count; ++i) {
 
+    // We don't have to compare soft-clean pages:
+    if (ref_page_numbers && pagemap && !(pagemap[i] & SOFT_DIRTY)) {
+      pagenos_[i] = ref_page_numbers[i];
+      store_->ref_page(ref_page_numbers[i]);
+      continue;
+    }
+
       remote_ptr<void> page = remote(addr.address() + (i << xbt_pagebits));
       xbt_assert(mc_page_offset((void*)page.address())==0,
         "Not at the beginning of a page");