Changeset 6e75f2d in mainline for kernel/generic/src/adt/bitmap.c

Timestamp:

2013-09-12T11:45:34Z (11 years ago)

Author:

Martin Decky <martin@…>

Branches:

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

Children:

3731d31

Parents:

c5396c1

Message:

optimize bitmap allocation using the next-fit algorithm

File:

• kernel/generic/src/adt/bitmap.c (modified) (10 diffs)

kernel/generic/src/adt/bitmap.c

@@ -100 +100 @@
         bitmap->elements = elements;
         bitmap->bits = (uint8_t *) data;
+        bitmap->next_fit = 0;
 }
 
@@ -116 +117 @@
                 return;
         
+        size_t start_byte = start / BITMAP_ELEMENT;
         size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
         
@@ -129 +131 @@
         if (start + count < aligned_start) {
                 /* Set bits in the middle of byte. */
-                bitmap->bits[start / BITMAP_ELEMENT] |=
+                bitmap->bits[start_byte] |=
                     ((1 << lub) - 1) << (start & BITMAP_REMAINER);
                 return;
@@ -136 +138 @@
         if (lub) {
                 /* Make sure to set any leading unaligned bits. */
-                bitmap->bits[start / BITMAP_ELEMENT] |=
+                bitmap->bits[start_byte] |=
                     ~((1 << (BITMAP_ELEMENT - lub)) - 1);
         }
@@ -169 +171 @@
                 return;
         
+        size_t start_byte = start / BITMAP_ELEMENT;
         size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
         
@@ -182 +185 @@
         if (start + count < aligned_start) {
                 /* Set bits in the middle of byte */
-                bitmap->bits[start / BITMAP_ELEMENT] &=
+                bitmap->bits[start_byte] &=
                     ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
                 return;
@@ -189 +192 @@
         if (lub) {
                 /* Make sure to clear any leading unaligned bits. */
-                bitmap->bits[start / BITMAP_ELEMENT] &=
+                bitmap->bits[start_byte] &=
                     (1 << (BITMAP_ELEMENT - lub)) - 1;
         }
@@ -206 +209 @@
                     ~((1 << tab) - 1);
         }
+        
+        bitmap->next_fit = start_byte;
 }
 
@@ -269 +274 @@
                 return false;
         
-        size_t bytes = bitmap_size(bitmap->elements);
-        
-        for (size_t byte = 0; byte < bytes; byte++) {
+        size_t size = bitmap_size(bitmap->elements);
+        
+        for (size_t pos = 0; pos < size; pos++) {
+                size_t byte = (bitmap->next_fit + pos) % size;
+                
                 /* Skip if the current byte has all bits set */
                 if (bitmap->bits[byte] == ALL_ONES)
@@ -288 +295 @@
                         
                         if (!bitmap_get_fast(bitmap, i)) {
-                                bool continuous = true;
+                                size_t continuous = 1;
                                 
                                 for (size_t j = 1; j < count; j++) {
-                                        if ((i + j >= bitmap->elements) ||
-                                            (bitmap_get_fast(bitmap, i + j))) {
-                                                continuous = false;
+                                        if ((i + j < bitmap->elements) &&
+                                            (!bitmap_get_fast(bitmap, i + j)))
+                                                continuous++;
+                                        else
                                                 break;
-                                        }
                                 }
                                 
-                                if (continuous) {
+                                if (continuous == count) {
                                         if (index != NULL) {
                                                 bitmap_set_range(bitmap, i, count);
+                                                bitmap->next_fit = i / BITMAP_ELEMENT;
                                                 *index = i;
                                         }
                                         
                                         return true;
-                                }
+                                } else
+                                        i += continuous;
                         }
                 }