Changeset c5396c1 in mainline for kernel/generic/include/adt/bitmap.h

Timestamp:

2013-09-12T10:27:17Z (11 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

6e75f2d

Parents:

4a5f2b0

Message:

abandon the 2nd level bitmap
according to observations it is very rare to have allocation requests for more than 8 frames, therefore the conservative update of the 2nd level bitmap can hardly provide any benefits
the natural blocking of the bitmap (by bytes) should provide a reasonable performance

File:

• kernel/generic/include/adt/bitmap.h (modified) (3 diffs)

kernel/generic/include/adt/bitmap.h

@@ -44 +44 @@
         size_t elements;
         uint8_t *bits;
-        
-        size_t block_size;
-        uint8_t *blocks;
 } bitmap_t;
 
@@ -52 +49 @@
     unsigned int value)
 {
-        if (element < bitmap->elements) {
-                /*
-                 * The 2nd level bitmap is conservative.
-                 * Make sure we update it properly.
-                 */
-                
-                if (value) {
-                        bitmap->bits[element / BITMAP_ELEMENT] |=
-                            (1 << (element & BITMAP_REMAINER));
-                } else {
-                        bitmap->bits[element / BITMAP_ELEMENT] &=
-                            ~(1 << (element & BITMAP_REMAINER));
-                        
-                        if (bitmap->block_size > 0) {
-                                size_t block = element / bitmap->block_size;
-                                
-                                bitmap->blocks[block / BITMAP_ELEMENT] &=
-                                    ~(1 << (block & BITMAP_REMAINER));
-                        }
-                }
+        if (element >= bitmap->elements)
+                return;
+        
+        size_t byte = element / BITMAP_ELEMENT;
+        uint8_t mask = 1 << (element & BITMAP_REMAINER);
+        
+        if (value) {
+                bitmap->bits[byte] |= mask;
+        } else {
+                bitmap->bits[byte] &= ~mask;
         }
 }
@@ -80 +67 @@
                 return 0;
         
-        return !!((bitmap->bits)[element / BITMAP_ELEMENT] &
-            (1 << (element & BITMAP_REMAINER)));
+        size_t byte = element / BITMAP_ELEMENT;
+        uint8_t mask = 1 << (element & BITMAP_REMAINER);
+        
+        return !!((bitmap->bits)[byte] & mask);
 }
 
-extern size_t bitmap_size(size_t, size_t);
-extern void bitmap_initialize(bitmap_t *, size_t, size_t, void *);
+extern size_t bitmap_size(size_t);
+extern void bitmap_initialize(bitmap_t *, size_t, void *);
 
 extern void bitmap_set_range(bitmap_t *, size_t, size_t);