Here's the patch to free_memory_available() in mm/page_alloc.c.
The comment above the source code should give you enough
info to get started on my algoritm...
Please verify it, I've only compiled it :-(, but it
should be correct nevertheless... (just remember to
read it first).
The patch is against 2.1.89-pre2, but judging from the
posts to linux-kernel, it should apply to newer versions
without a hitch.
Rik.
+-----------------------------+------------------------------+
| For Linux mm-patches, go to | "I'm busy managing memory.." |
| my homepage (via LinuxHQ). | H.H.vanRiel@fys.ruu.nl |
| ...submissions welcome... | http://www.fys.ruu.nl/~riel/ |
+-----------------------------+------------------------------+
-----------------------> cut here <------------------------------
--- page_alloc.pre89-2 Mon Mar 2 23:32:16 1998
+++ page_alloc.c Tue Mar 3 00:03:48 1998
@@ -108,22 +108,51 @@
* but this had better return false if any reasonable "get_free_page()"
* allocation could currently fail..
*
- * Right now we just require that the highest memory order should
- * have at least two entries. Whether this makes sense or not
- * under real load is to be tested, but it also gives us some
- * guarantee about memory fragmentation (essentially, it means
- * that there should be at least two large areas available).
+ * Currently we approve of the following situations:
+ * - the highest memory order has two entries
+ * - the highest memory order has one free entry and:
+ * - the next-highest memory order has two free entries
+ * - the highest memory order has one free entry and:
+ * - the next-highest memory order has one free entry
+ * - the next-next-highest memory order has two free entries
+ *
+ * [previously, there had to be two entries of the highest memory
+ * order, but this lead to problems on large-memory machines.]
*/
int free_memory_available(void)
{
- int retval;
+ int retval = 0;
unsigned long flags;
- struct free_area_struct * last = free_area + NR_MEM_LISTS - 1;
+ struct free_area_struct * biggest = free_area + NR_MEM_LISTS - 1;
+ struct free_area_struct * bigger = free_area + NR_MEM_LISTS - 2;
+ struct free_area_struct * big = free_area + NR_MEM_LISTS - 3;
spin_lock_irqsave(&page_alloc_lock, flags);
- retval = (last->next != memory_head(last)) && (last->next->next != memory_head(last));
+ if (biggest->next != memory_head(biggest)) {
+ retval = 4;
+ if (biggest->next->next != memory_head(biggest))
+ retval += 4;
+ } else {
+ /* we want at least one free area of the 'biggest' size */
+ goto out;
+ }
+ if (bigger->next != memory_head(bigger)) {
+ retval += 2;
+ if (bigger->next->next != memory_head(bigger))
+ retval += 2;
+ } else {
+ /* if we have only one free area of the 'biggest' size, we also
+ * want one of the 'bigger' size */
+ goto out;
+ }
+ if (big->next != memory_head(big)) {
+ retval += 1;
+ if (big->next->next != memory_head(big))
+ retval += 1;
+ }
+out:
spin_unlock_irqrestore(&page_alloc_lock, flags);
- return retval;
+ return retval > 7;
}
static inline void free_pages_ok(unsigned long map_nr, unsigned long order)
-
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