Changes in kernel/generic/src/adt/bitmap.c [7de18418:f72906c] in mainline

File:

• kernel/generic/src/adt/bitmap.c (modified) (11 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.
- *
  */
 
@@ -56 +48 @@
 #define ALL_ZEROES  0x00
 
+/** Unchecked version of bitmap_get()
+ *
+ * This version of bitmap_get() does not do any boundary checks.
+ *
+ * @param bitmap  Bitmap to access.
+ * @param element Element to access.
+ *
+ * @return Bit value of the element in the bitmap.
+ *
+ */
+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);
+}
+
 /** Get bitmap size
  *
@@ -61 +71 @@
  *
  * @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 block_size)
+size_t bitmap_size(size_t elements)
 {
         size_t size = elements / BITMAP_ELEMENT;
@@ -74 +82 @@
                 size++;
         
-        if (block_size > 0) {
-                size += elements / block_size;
-                
-                if ((elements % block_size) != 0)
-                        size++;
-        }
-        
         return size;
 }
@@ -90 +91 @@
  * @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
@@ -97 +96 @@
  *
  */
-void bitmap_initialize(bitmap_t *bitmap, size_t elements, size_t block_size,
-    void *data)
+void bitmap_initialize(bitmap_t *bitmap, size_t elements, void *data)
 {
         bitmap->elements = elements;
         bitmap->bits = (uint8_t *) data;
-        
-        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;
-        }
+        bitmap->next_fit = 0;
 }
 
@@ -166 +114 @@
         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);
         
@@ -202 +130 @@
         
         if (start + count < aligned_start) {
-                /* Set bits in the middle of byte */
-                bits[start / BITMAP_ELEMENT] &=
-                    ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
+                /* 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. */
-                bits[start / BITMAP_ELEMENT] &=
-                    (1 << (BITMAP_ELEMENT - lub)) - 1;
+                /* Make sure to set any leading unaligned bits. */
+                bitmap->bits[start_byte] |=
+                    ~((1 << (BITMAP_ELEMENT - lub)) - 1);
         }
         
@@ -217 +145 @@
         
         for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
-                /* The middle bits can be cleared byte by byte. */
-                bits[aligned_start / BITMAP_ELEMENT + i] = ALL_ZEROES;
+                /* The middle bits can be set byte by byte. */
+                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] =
+                    ALL_ONES;
         }
         
         if (tab) {
-                /* Make sure to clear any trailing aligned bits. */
-                bits[aligned_start / BITMAP_ELEMENT + i] &= ~((1 << tab) - 1);
+                /* Make sure to set any trailing aligned bits. */
+                bitmap->bits[aligned_start / BITMAP_ELEMENT + i] |=
+                    (1 << tab) - 1;
         }
 }
@@ -238 +168 @@
         ASSERT(start + count <= bitmap->elements);
         
-        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);
-        }
+        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;
 }
 
@@ -280 +238 @@
 }
 
+static int constraint_satisfy(size_t index, size_t base, size_t constraint)
+{
+        return (((base + index) & constraint) == 0);
+}
+
+/** Find a continuous zero bit range
+ *
+ * Find a continuous zero bit range in the bitmap. The address
+ * computed as the sum of the index of the first zero bit and
+ * the base argument needs to be compliant with the constraint
+ * (those bits that are set in the constraint cannot be set in
+ * the address).
+ *
+ * If the index argument is non-NULL, the continuous zero range
+ * is set and the index of the first bit is stored to index.
+ * Otherwise the bitmap stays untouched.
+ *
+ * @param bitmap     Bitmap structure.
+ * @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
+ *                   bit. Can be NULL (in which case the bitmap
+ *                   is not modified).
+ *
+ * @return Non-zero if a continuous range of zero bits satisfying
+ *         the constraint has been found.
+ * @return Zero otherwise.
+ *
+ */
+int bitmap_allocate_range(bitmap_t *bitmap, size_t count, size_t base,
+    size_t prefered, 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;
+                
+                /* Skip if the current byte has all bits set */
+                if (bitmap->bits[byte] == ALL_ONES)
+                        continue;
+                
+                size_t byte_bit = byte * BITMAP_ELEMENT;
+                
+                for (size_t bit = 0; bit < BITMAP_ELEMENT; bit++) {
+                        size_t i = byte_bit + bit;
+                        
+                        if (i >= bitmap->elements)
+                                break;
+                        
+                        if (!constraint_satisfy(i, base, constraint))
+                                continue;
+                        
+                        if (!bitmap_get_fast(bitmap, i)) {
+                                size_t continuous = 1;
+                                
+                                for (size_t j = 1; j < count; j++) {
+                                        if ((i + j < bitmap->elements) &&
+                                            (!bitmap_get_fast(bitmap, i + j)))
+                                                continuous++;
+                                        else
+                                                break;
+                                }
+                                
+                                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;
+                        }
+                }
+        }
+        
+        return false;
+}
+
 /** @}
  */