Changeset ecbdc724 in mainline for genarch/src/mm/page_pt.c

Timestamp:

2006-02-10T22:37:27Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

d7d6385

Parents:

0882a9a

Message:

Change pt_mapping_remove() to deallocate frames for empty PTL1, PTL2 and PTL3.

File:

• genarch/src/mm/page_pt.c (modified) (3 diffs)

genarch/src/mm/page_pt.c

@@ -104 +104 @@
  * this call visible.
  *
+ * Empty page tables except PTL0 are freed.
+ *
  * The address space must be locked and interrupts must be disabled.
  *
@@ -112 +114 @@
 {
         pte_t *ptl0, *ptl1, *ptl2, *ptl3;
+        bool empty = true;
+        int i;
+
+        /*
+         * First, remove the mapping, if it exists.
+         */
 
         ptl0 = (pte_t *) PA2KA((__address) as->page_table);
@@ -132 +140 @@
         /* Destroy the mapping. Setting to PAGE_NOT_PRESENT is not sufficient. */
         memsetb((__address) &ptl3[PTL3_INDEX(page)], sizeof(pte_t), 0);
+
+        /*
+         * Second, free all empty tables along the way from PTL3 down to PTL0.
+         */
+        
+        /* check PTL3 */
+        for (i = 0; i < PTL3_ENTRIES; i++) {
+                if (PTE_VALID(&ptl3[i])) {
+                        empty = false;
+                        break;
+                }
+        }
+        if (empty) {
+                /*
+                 * PTL3 is empty.
+                 * Release the frame and remove PTL3 pointer from preceding table.
+                 */
+                frame_free(ADDR2PFN(KA2PA((__address) ptl3)));
+                if (PTL2_ENTRIES)
+                        memsetb((__address) &ptl2[PTL2_INDEX(page)], sizeof(pte_t), 0);
+                else if (PTL1_ENTRIES)
+                        memsetb((__address) &ptl1[PTL1_INDEX(page)], sizeof(pte_t), 0);
+                else
+                        memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
+        } else {
+                /*
+                 * PTL3 is not empty.
+                 * Therefore, there must be a path from PTL0 to PTL3 and
+                 * thus nothing to free in higher levels.
+                 */
+                return;
+        }
+        
+        /* check PTL2, empty is still true */
+        if (PTL2_ENTRIES) {
+                for (i = 0; i < PTL2_ENTRIES; i++) {
+                        if (PTE_VALID(&ptl2[i])) {
+                                empty = false;
+                                break;
+                        }
+                }
+                if (empty) {
+                        /*
+                         * PTL2 is empty.
+                         * Release the frame and remove PTL2 pointer from preceding table.
+                         */
+                        frame_free(ADDR2PFN(KA2PA((__address) ptl2)));
+                        if (PTL1_ENTRIES)
+                                memsetb((__address) &ptl1[PTL1_INDEX(page)], sizeof(pte_t), 0);
+                        else
+                                memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
+                }
+                else {
+                        /*
+                         * PTL2 is not empty.
+                         * Therefore, there must be a path from PTL0 to PTL2 and
+                         * thus nothing to free in higher levels.
+                         */
+                        return;
+                }
+        }
+
+        /* check PTL1, empty is still true */
+        if (PTL1_ENTRIES) {
+                for (i = 0; i < PTL1_ENTRIES; i++) {
+                        if (PTE_VALID(&ptl1[i])) {
+                                empty = false;
+                                break;
+                        }
+                }
+                if (empty) {
+                        /*
+                         * PTL1 is empty.
+                         * Release the frame and remove PTL1 pointer from preceding table.
+                         */
+                        frame_free(ADDR2PFN(KA2PA((__address) ptl1)));
+                        memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
+                }
+        }
+
 }