sequential option for mmap SERVER-607

Conflicts:

	db/extsort.cpp

4 files changed, 21 insertions, 5 deletions

diff --git a/db/extsort.cpp b/db/extsort.cpp
index 949c2e66500..751c63e650f 100644
--- a/db/extsort.cpp
+++ b/db/extsort.cpp
@@ -204,7 +204,8 @@ namespace mongo {
     
     BSONObjExternalSorter::FileIterator::FileIterator( string file ){
         long length;
-        _buf = (char*)_file.map( file.c_str() , length );
+        _buf = (char*)_file.map( file.c_str() , length , MemoryMappedFile::SEQUENTIAL );
+        massert( "mmap failed" , _buf );
         assert( (unsigned long)length == file_size( file ) );
         _end = _buf + length;
     }
diff --git a/util/mmap.h b/util/mmap.h
index ed4ca99c326..140f33a5bd1 100644
--- a/util/mmap.h
+++ b/util/mmap.h
@@ -22,6 +22,10 @@ namespace mongo {
     class MemoryMappedFile {
     public:
 
+        enum Options {
+            SEQUENTIAL = 1
+        };
+
         MemoryMappedFile();
         ~MemoryMappedFile(); /* closes the file if open */
         void close();
@@ -32,7 +36,7 @@ namespace mongo {
         /* Creates with length if DNE, otherwise uses existing file length,
            passed length.
         */
-        void* map(const char *filename, long &length);
+        void* map(const char *filename, long &length, int options = 0 );
 
         void flush(bool sync);
 
diff --git a/util/mmap_posix.cpp b/util/mmap_posix.cpp
index 25deb871f92..5acedf1f752 100644
--- a/util/mmap_posix.cpp
+++ b/util/mmap_posix.cpp
@@ -49,7 +49,7 @@ namespace mongo {
 #define O_NOATIME 0
 #endif
 
-    void* MemoryMappedFile::map(const char *filename, long &length) {
+    void* MemoryMappedFile::map(const char *filename, long &length, int options) {
         // length may be updated by callee.
         theFileAllocator().allocateAsap( filename, length );
         len = length;
@@ -76,9 +76,16 @@ namespace mongo {
             }
             return 0;
         }
+        
+        if ( options & SEQUENTIAL ){
+            if ( madvise( view , length , MADV_SEQUENTIAL ) ){
+                out() << " madvise failed for " << filename << " " << errno << endl;
+            }
+        }
+        
         return view;
     }
-
+    
     void MemoryMappedFile::flush(bool sync) {
         if ( view == 0 || fd == 0 )
             return;
diff --git a/util/mmap_win.cpp b/util/mmap_win.cpp
index 32528342b42..7db43601b13 100644
--- a/util/mmap_win.cpp
+++ b/util/mmap_win.cpp
@@ -69,9 +69,13 @@ namespace mongo {
         updateLength( filename, length );
         std::wstring filenamew = toWideString(filename);
 
+        DWORD createOptions = FILE_ATTRIBUTE_NORMAL;
+        if ( options & SEQUENTIAL )
+            createOptions |= FILE_FLAG_SEQUENTIAL_SCAN;
+
         fd = CreateFile(
                  filenamew.c_str(), GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ,
-                 NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+                 NULL, OPEN_ALWAYS, createOptions , NULL);
         if ( fd == INVALID_HANDLE_VALUE ) {
             out() << "Create/OpenFile failed " << filename << ' ' << GetLastError() << endl;
             return 0;