Changes in kernel/generic/src/adt/bitmap.c [f72906c:64f3d3b] in mainline

File:

• kernel/generic/src/adt/bitmap.c (modified) (13 diffs)

kernel/generic/src/adt/bitmap.c

@@ -37 +37 @@
  * setting and clearing ranges of bits and for finding ranges
  * of unset bits.
+ *
+ * The bitmap ADT can optionally implement a two-level hierarchy
+ * for faster range searches. The second level bitmap (of blocks)
+ * is not precise, but conservative. This means that if the block
+ * bit is set, it guarantees that all bits in the block are set.
+ * But if the block bit is unset, nothing can be said about the
+ * bits in the block.
+ *
  */
 
@@ -48 +56 @@
 #define ALL_ZEROES  0x00
 
+/** Compute the size of a bitmap
+ *
+ * Compute the size of a bitmap that can store given number
+ * of elements.
+ *
+ * @param elements Number of elements to store.
+ *
+ * @return Size of the bitmap (in units of BITMAP_ELEMENT bits).
+ *
+ */
+static size_t bitmap_bytes(size_t elements)
+{
+        size_t bytes = elements / BITMAP_ELEMENT;
+        
+        if ((elements % BITMAP_ELEMENT) != 0)
+                bytes++;
+        
+        return bytes;
+}
+
+/** Compute the number of 2nd level blocks
+ *
+ * Compute the number of 2nd level blocks for a given number
+ * of elements.
+ *
+ * @param elements   Number of elements.
+ * @param block_size Number of elements in one block.
+ *
+ * @return Number of 2nd level blocks.
+ * @return Zero if block_size is zero.
+ *
+ */
+static size_t bitmap_blocks(size_t elements, size_t block_size)
+{
+        if (block_size == 0)
+                return 0;
+        
+        size_t blocks = elements / block_size;
+        
+        if ((elements % block_size) != 0)
+                blocks++;
+        
+        return blocks;
+}
+
 /** Unchecked version of bitmap_get()
  *
@@ -60 +113 @@
 static unsigned int bitmap_get_fast(bitmap_t *bitmap, size_t element)
 {
-        size_t byte = element / BITMAP_ELEMENT;
-        uint8_t mask = 1 << (element & BITMAP_REMAINER);
-        
-        return !!((bitmap->bits)[byte] & mask);
+        return !!((bitmap->bits)[element / BITMAP_ELEMENT] &
+            (1 << (element & BITMAP_REMAINER)));
 }
 
@@ -71 +122 @@
  *
  * @param elements   Number bits stored in bitmap.
+ * @param block_size Block size of the 2nd level bitmap.
+ *                   If set to zero, no 2nd level is used.
  *
  * @return Size (in bytes) required for the bitmap.
  *
  */
-size_t bitmap_size(size_t elements)
-{
-        size_t size = elements / BITMAP_ELEMENT;
-        
-        if ((elements % BITMAP_ELEMENT) != 0)
-                size++;
-        
-        return size;
+size_t bitmap_size(size_t elements, size_t block_size)
+{
+        size_t blocks = bitmap_blocks(elements, block_size);
+        
+        return (bitmap_bytes(elements) + bitmap_bytes(blocks));
 }
 
@@ -91 +141 @@
  * @param bitmap     Bitmap structure.
  * @param elements   Number of bits stored in bitmap.
+ * @param block_size Block size of the 2nd level bitmap.
+ *                   If set to zero, no 2nd level is used.
  * @param data       Address of the memory used to hold the map.
  *                   The optional 2nd level bitmap follows the 1st
@@ -96 +148 @@
  *
  */
-void bitmap_initialize(bitmap_t *bitmap, size_t elements, void *data)
+void bitmap_initialize(bitmap_t *bitmap, size_t elements, size_t block_size,
+    void *data)
 {
         bitmap->elements = elements;
         bitmap->bits = (uint8_t *) data;
-        bitmap->next_fit = 0;
+        
+        if (block_size > 0) {
+                bitmap->block_size = block_size;
+                bitmap->blocks = bitmap->bits +
+                    bitmap_size(elements, 0);
+        } else {
+                bitmap->block_size = 0;
+                bitmap->blocks = NULL;
+        }
+}
+
+static void bitmap_set_range_internal(uint8_t *bits, size_t start, size_t count)
+{
+        if (count == 0)
+                return;
+        
+        size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
+        
+        /* Leading unaligned bits */
+        size_t lub = min(aligned_start - start, count);
+        
+        /* Aligned middle bits */
+        size_t amb = (count > lub) ? (count - lub) : 0;
+        
+        /* Trailing aligned bits */
+        size_t tab = amb % BITMAP_ELEMENT;
+        
+        if (start + count < aligned_start) {
+                /* Set bits in the middle of byte. */
+                bits[start / BITMAP_ELEMENT] |=
+                    ((1 << lub) - 1) << (start & BITMAP_REMAINER);
+                return;
+        }
+        
+        if (lub) {
+                /* Make sure to set any leading unaligned bits. */
+                bits[start / BITMAP_ELEMENT] |=
+                    ~((1 << (BITMAP_ELEMENT - lub)) - 1);
+        }
+        
+        size_t i;
+        
+        for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
+                /* The middle bits can be set byte by byte. */
+                bits[aligned_start / BITMAP_ELEMENT + i] = ALL_ONES;
+        }
+        
+        if (tab) {
+                /* Make sure to set any trailing aligned bits. */
+                bits[aligned_start / BITMAP_ELEMENT + i] |= (1 << tab) - 1;
+        }
 }
 
@@ -114 +217 @@
         ASSERT(start + count <= bitmap->elements);
         
+        bitmap_set_range_internal(bitmap->bits, start, count);
+        
+        if (bitmap->block_size > 0) {
+                size_t aligned_start = ALIGN_UP(start, bitmap->block_size);
+                
+                /* Leading unaligned bits */
+                size_t lub = min(aligned_start - start, count);
+                
+                /* Aligned middle bits */
+                size_t amb = (count > lub) ? (count - lub) : 0;
+                
+                size_t aligned_size = amb / bitmap->block_size;
+                
+                bitmap_set_range_internal(bitmap->blocks, aligned_start,
+                    aligned_size);
+        }
+}
+
+static void bitmap_clear_range_internal(uint8_t *bits, size_t start,
+    size_t count)
+{
         if (count == 0)
                 return;
         
-        size_t start_byte = start / BITMAP_ELEMENT;
         size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
         
@@ -130 +253 @@
         
         if (start + count < aligned_start) {
-                /* Set bits in the middle of byte. */
-                bitmap->bits[start_byte] |=
-                    ((1 << lub) - 1) << (start & BITMAP_REMAINER);
+                /* Set bits in the middle of byte */
+                bits[start / BITMAP_ELEMENT] &=
+                    ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
                 return;
         }
         
         if (lub) {
-                /* Make sure to set any leading unaligned bits. */
-                bitmap->bits[start_byte] |=
-                    ~((1 << (BITMAP_ELEMENT - lub)) - 1);
+                /* Make sure to clear any leading unaligned bits. */
+                bits[start / BITMAP_ELEMENT] &=
+                    (1 << (BITMAP_ELEMENT - lub)) - 1;
         }
         
@@ -145 +268 @@
         
         for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
-                /* The middle bits can be set byte by byte. */
-                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] =
-                    ALL_ONES;
+                /* The middle bits can be cleared byte by byte. */
+                bits[aligned_start / BITMAP_ELEMENT + i] = ALL_ZEROES;
         }
         
         if (tab) {
-                /* Make sure to set any trailing aligned bits. */
-                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] |=
-                    (1 << tab) - 1;
+                /* Make sure to clear any trailing aligned bits. */
+                bits[aligned_start / BITMAP_ELEMENT + i] &= ~((1 << tab) - 1);
         }
 }
@@ -168 +289 @@
         ASSERT(start + count <= bitmap->elements);
         
-        if (count == 0)
-                return;
-        
-        size_t start_byte = start / BITMAP_ELEMENT;
-        size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
-        
-        /* Leading unaligned bits */
-        size_t lub = min(aligned_start - start, count);
-        
-        /* Aligned middle bits */
-        size_t amb = (count > lub) ? (count - lub) : 0;
-        
-        /* Trailing aligned bits */
-        size_t tab = amb % BITMAP_ELEMENT;
-        
-        if (start + count < aligned_start) {
-                /* Set bits in the middle of byte */
-                bitmap->bits[start_byte] &=
-                    ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
-                return;
-        }
-        
-        if (lub) {
-                /* Make sure to clear any leading unaligned bits. */
-                bitmap->bits[start_byte] &=
-                    (1 << (BITMAP_ELEMENT - lub)) - 1;
-        }
-        
-        size_t i;
-        
-        for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
-                /* The middle bits can be cleared byte by byte. */
-                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] =
-                    ALL_ZEROES;
-        }
-        
-        if (tab) {
-                /* Make sure to clear any trailing aligned bits. */
-                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] &=
-                    ~((1 << tab) - 1);
-        }
-        
-        bitmap->next_fit = start_byte;
+        bitmap_clear_range_internal(bitmap->bits, start, count);
+        
+        if (bitmap->block_size > 0) {
+                size_t aligned_start = start / bitmap->block_size;
+                
+                size_t aligned_end = (start + count) / bitmap->block_size;
+                
+                if (((start + count) % bitmap->block_size) != 0)
+                        aligned_end++;
+                
+                size_t aligned_size = aligned_end - aligned_start;
+                
+                bitmap_clear_range_internal(bitmap->blocks, aligned_start,
+                    aligned_size);
+        }
 }
 
@@ -258 +351 @@
  * @param count      Number of continuous zero bits to find.
  * @param base       Address of the first bit in the bitmap.
- * @param prefered   Prefered address to start searching from.
  * @param constraint Constraint for the address of the first zero bit.
  * @param index      Place to store the index of the first zero
@@ -270 +362 @@
  */
 int bitmap_allocate_range(bitmap_t *bitmap, size_t count, size_t base,
-    size_t prefered, size_t constraint, size_t *index)
+    size_t constraint, size_t *index)
 {
         if (count == 0)
                 return false;
         
-        size_t size = bitmap_size(bitmap->elements);
-        size_t next_fit = bitmap->next_fit;
-        
-        /*
-         * Adjust the next-fit value according to the address
-         * the caller prefers to start the search at.
-         */
-        if ((prefered > base) && (prefered < base + bitmap->elements)) {
-                size_t prefered_fit = (prefered - base) / BITMAP_ELEMENT;
-                
-                if (prefered_fit > next_fit)
-                        next_fit = prefered_fit;
-        }
-        
-        for (size_t pos = 0; pos < size; pos++) {
-                size_t byte = (next_fit + pos) % size;
-                
+        size_t bytes = bitmap_bytes(bitmap->elements);
+        
+        for (size_t byte = 0; byte < bytes; byte++) {
                 /* Skip if the current byte has all bits set */
                 if (bitmap->bits[byte] == ALL_ONES)
@@ -308 +386 @@
                         
                         if (!bitmap_get_fast(bitmap, i)) {
-                                size_t continuous = 1;
+                                bool continuous = true;
                                 
                                 for (size_t j = 1; j < count; j++) {
-                                        if ((i + j < bitmap->elements) &&
-                                            (!bitmap_get_fast(bitmap, i + j)))
-                                                continuous++;
-                                        else
+                                        if ((i + j >= bitmap->elements) ||
+                                            (bitmap_get_fast(bitmap, i + j))) {
+                                                continuous = false;
                                                 break;
+                                        }
                                 }
                                 
-                                if (continuous == count) {
+                                if (continuous) {
                                         if (index != NULL) {
                                                 bitmap_set_range(bitmap, i, count);
-                                                bitmap->next_fit = i / BITMAP_ELEMENT;
                                                 *index = i;
                                         }
                                         
                                         return true;
-                                } else
-                                        i += continuous;
+                                }
                         }
                 }