[PATCH 8/8] Direct Migration V2: SWAP_REFERENCE for try_to_unmap()

Christoph Lameter
2005-11-08T21:04:58Z

Distinguish in try_to_umap_one between the case when the page is truly
unswappable from the case when the page was recently referenced.

The page migration code uses try_to_unmap_one and can avoid calling
try_to_unmap again if there was a persistent failure.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.14-mm1/include/linux/rmap.h
===================================================================
--- linux-2.6.14-mm1.orig/include/linux/rmap.h 2005-11-07 18:18:14.000000000 -0800
+++ linux-2.6.14-mm1/include/linux/rmap.h 2005-11-07 18:48:11.000000000 -0800
@@ -120,6 +120,7 @@ unsigned long page_address_in_vma(struct
*/
#define SWAP_SUCCESS 0
#define SWAP_AGAIN 1
-#define SWAP_FAIL 2
+#define SWAP_REFERENCE 2
+#define SWAP_FAIL 3

#endif /* _LINUX_RMAP_H */
Index: linux-2.6.14-mm1/mm/rmap.c
===================================================================
--- linux-2.6.14-mm1.orig/mm/rmap.c 2005-11-07 18:18:14.000000000 -0800
+++ linux-2.6.14-mm1/mm/rmap.c 2005-11-07 18:48:11.000000000 -0800
@@ -546,16 +546,20 @@ static int try_to_unmap_one(struct page

/*
* If the page is mlock()d, we cannot swap it out.
- * If it's recently referenced (perhaps page_referenced
- * skipped over this mm) then we should reactivate it.
- *
* Pages belonging to VM_RESERVED regions should not happen here.
*/
- if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
- ptep_clear_flush_young(vma, address, pte)) {
+ if (vma->vm_flags & (VM_LOCKED|VM_RESERVED)) {
ret = SWAP_FAIL;
goto out_unmap;
}
+ /*
+ * If the page is recently referenced (perhaps page_referenced
+ * skipped over this mm) then we may want to reactivate it.
+ */
+ if (ptep_clear_flush_young(vma, address, pte)) {
+ ret = SWAP_REFERENCE;
+ goto out_unmap;
+ }

/* Nuke the page table entry. */
flush_cache_page(vma, address, page_to_pfn(page));
@@ -706,7 +710,9 @@ static int try_to_unmap_anon(struct page

list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
ret = try_to_unmap_one(page, vma);
- if (ret == SWAP_FAIL || !page_mapped(page))
+ if (ret == SWAP_FAIL ||
+ ret == SWAP_REFERENCE ||
+ !page_mapped(page))
break;
}
spin_unlock(&anon_vma->lock);
@@ -737,7 +743,9 @@ static int try_to_unmap_file(struct page
spin_lock(&mapping->i_mmap_lock);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
ret = try_to_unmap_one(page, vma);
- if (ret == SWAP_FAIL || !page_mapped(page))
+ if (ret == SWAP_FAIL ||
+ ret == SWAP_REFERENCE ||
+ !page_mapped(page))
goto out;
}

@@ -822,7 +830,9 @@ out:
*
* SWAP_SUCCESS - we succeeded in removing all mappings
* SWAP_AGAIN - we missed a mapping, try again later
+ * SWAP_REFERENCE - the page was recently referenced
* SWAP_FAIL - the page is unswappable
+ *
*/
int try_to_unmap(struct page *page)
{
Index: linux-2.6.14-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.14-mm1.orig/mm/vmscan.c 2005-11-07 18:38:59.000000000 -0800
+++ linux-2.6.14-mm1/mm/vmscan.c 2005-11-07 18:51:25.000000000 -0800
@@ -471,6 +471,7 @@ static int shrink_list(struct list_head
*/
if (page_mapped(page) && mapping) {
switch (try_to_unmap(page)) {
+ case SWAP_REFERENCE:
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
@@ -689,8 +690,9 @@ int migrate_page_remove_references(struc
for(i = 0; i < 10 && page_mapped(page); i++) {
int rc = try_to_unmap(page);

- if (rc == SWAP_SUCCESS)
+ if (rc == SWAP_SUCCESS || rc == SWAP_FAIL)
break;
+
/*
* If there are other runnable processes then running
* them may make it possible to unmap the page