Use mmap() IO for reading uncompressed .blends

Instead of submitting tons of tiny IO syscalls, we can speed things up
significantly by `mmap`ing the .blend file into virtual memory and directly
accessing it.

In my local testing, this speeds up loading the Dweebs file with all its
linked files from 19sec to 10sec (on Linux).

As far as I can see, this should be supported on Linux, OSX and BSD.
For Windows, a second code path uses `CreateFileMapping` and
`MapViewOfFile` to achieve the same result.

Reviewed By: mont29, brecht

Differential Revision: https://developer.blender.org/D8246

1 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/blenloader/intern/readfile.h b/source/blender/blenloader/intern/readfile.h
index c724cc32051..86f05eda7b7 100644
--- a/source/blender/blenloader/intern/readfile.h
+++ b/source/blender/blenloader/intern/readfile.h
@@ -41,6 +41,7 @@ struct Object;
 struct OldNewMap;
 struct ReportList;
 struct UserDef;
+struct BLI_mmap_file;
 
 typedef struct IDNameLib_Map IDNameLib_Map;
 
@@ -83,8 +84,9 @@ typedef struct FileData {
   /** Regular file reading. */
   int filedes;
 
-  /** Variables needed for reading from memory / stream. */
+  /** Variables needed for reading from memory / stream / memory-mapped files. */
   const char *buffer;
+  struct BLI_mmap_file *mmap_file;
   /** Variables needed for reading from memfile (undo). */
   struct MemFile *memfile;
   /** Whether we are undoing (< 0) or redoing (> 0), used to choose which 'unchanged' flag to use