Changeset f72906c in mainline for kernel/generic/src/adt/bitmap.c

Timestamp:

2013-09-12T18:09:51Z (11 years ago)

Author:

Martin Decky <martin@…>

Branches:

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

Children:

69f5f19

Parents:

b11f6fb

Message:

prefer allocating physical frames from the so called low priority memory (< 16 MB on ia32 and amd64)
this saves the high priority memory for legacy DMA transfers, etc.

File:

• kernel/generic/src/adt/bitmap.c (modified) (3 diffs)

kernel/generic/src/adt/bitmap.c

@@ -258 +258 @@
  * @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
@@ -269 +270 @@
  */
 int bitmap_allocate_range(bitmap_t *bitmap, size_t count, size_t base,
-    size_t constraint, size_t *index)
+    size_t prefered, size_t constraint, size_t *index)
 {
         if (count == 0)
@@ -275 +276 @@
         
         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 = (bitmap->next_fit + pos) % size;
+                size_t byte = (next_fit + pos) % size;
                 
                 /* Skip if the current byte has all bits set */