small hack to optimize our common case for snapshotting and set config option to...

hack assumes that same pages will be dirty across different executions so just copies them and doesn't reprotect them

diff --git a/config.h b/config.h
index 55093637a175186bddebb46b9a37b2f3a5117666..109e8d86097ab55c545705f0059c544bb01b9738 100644 (file)
--- a/config.h
+++ b/config.h
@@ -27,9 +27,11 @@
 
 /** Snapshotting configurables */
 
-/** If USE_MPROTECT_SNAPSHOT=1, then snapshot by using mmap() and mprotect()
+/** 
+ * If USE_MPROTECT_SNAPSHOT=2, then snapshot by tuned mmap() algorithm
+ * If USE_MPROTECT_SNAPSHOT=1, then snapshot by using mmap() and mprotect()
  * If USE_MPROTECT_SNAPSHOT=0, then snapshot by using fork() */
-#define USE_MPROTECT_SNAPSHOT 0
+#define USE_MPROTECT_SNAPSHOT 2
 
 /** Size of signal stack */
 #define SIGSTACKSIZE 32768

diff --git a/snapshot.cc b/snapshot.cc
index a1dcad581985ef7f1f9ae663a446a4fb4e5a333d..dadb75956c1f4254c3ecc84d519cd7431a8910af 100644 (file)
--- a/snapshot.cc
+++ b/snapshot.cc
@@ -283,6 +283,15 @@ snapshot_id takeSnapshot( ){
  *  @param theID is the snapshot identifier to rollback to.
  */
 void rollBack( snapshot_id theID ){
+#if USE_MPOTECT_SNAPSHOT==2
+       if (snapshotrecord->lastSnapShot==(theID+1)) {
+               for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
+                       memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
+               }
+               return;
+       }
+#endif
+
 #if USE_MPROTECT_SNAPSHOT
        HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
        for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {