On Tue, 10 Jan 2006, Andrew Morton wrote:
> So I'd suggest that this part needs a bit of a rethink. If we really need
> to run other processes then try a schedule_timeout_uninterruptible(1). If
> not, just remove the loop.
>
> Please stick a printk in there, work out how often and under which
> workloads that loop is actually doing something useful.
The loop is there to call try_to_unmap until it replaces all ptes
with swap ptes. The problem is that try_to_unmap may return SWAP_FAIL
if a pte was recently referenced and do nothing.
Lets go back to the way the old hotplug code did it. Modify
try_to_unmap() to take an additional parameter so that the reference
bit in the ptes does not cause a SWAP_FAIL. Another option would be to
modify try_to_unmap to return an additional status SWAP_REFERENCE and
call try_to_unmap until another status is returned.
Add a parameter to try_to_unmap and friends to not return
SWAP_FAIL if a newly referenced pte is encountered.
Then replace the loop in migrate_page_remove_references()
with an invokation of try_to_unmap with that parameter.
Signed-off-by: Christoph Lameter <[email protected]>
Index: linux-2.6.15/mm/vmscan.c
===================================================================
--- linux-2.6.15.orig/mm/vmscan.c 2006-01-11 19:22:01.000000000 -0800
+++ linux-2.6.15/mm/vmscan.c 2006-01-11 19:22:07.000000000 -0800
@@ -472,7 +472,7 @@ static int shrink_list(struct list_head
* processes. Try to unmap it here.
*/
if (page_mapped(page) && mapping) {
- switch (try_to_unmap(page)) {
+ switch (try_to_unmap(page, 0)) {
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
@@ -621,7 +621,7 @@ static int swap_page(struct page *page)
struct address_space *mapping = page_mapping(page);
if (page_mapped(page) && mapping)
- if (try_to_unmap(page) != SWAP_SUCCESS)
+ if (try_to_unmap(page, 0) != SWAP_SUCCESS)
goto unlock_retry;
if (PageDirty(page)) {
@@ -677,7 +677,6 @@ int migrate_page_remove_references(struc
{
struct address_space *mapping = page_mapping(page);
struct page **radix_pointer;
- int i;
/*
* Avoid doing any of the following work if the page count
@@ -706,17 +705,7 @@ int migrate_page_remove_references(struc
* If the page was not migrated then the PageSwapCache bit
* is still set and the operation may continue.
*/
- for(i = 0; i < 10 && page_mapped(page); i++) {
- int rc = try_to_unmap(page);
-
- if (rc == SWAP_SUCCESS)
- break;
- /*
- * If there are other runnable processes then running
- * them may make it possible to unmap the page
- */
- schedule();
- }
+ try_to_unmap(page, 1);
/*
* Give up if we were unable to remove all mappings.
Index: linux-2.6.15/mm/rmap.c
===================================================================
--- linux-2.6.15.orig/mm/rmap.c 2006-01-11 19:22:00.000000000 -0800
+++ linux-2.6.15/mm/rmap.c 2006-01-11 19:22:07.000000000 -0800
@@ -571,7 +571,8 @@ void page_remove_rmap(struct page *page)
* Subfunctions of try_to_unmap: try_to_unmap_one called
* repeatedly from either try_to_unmap_anon or try_to_unmap_file.
*/
-static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
+static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
+ int ignore_refs)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
@@ -594,7 +595,8 @@ static int try_to_unmap_one(struct page
* skipped over this mm) then we should reactivate it.
*/
if ((vma->vm_flags & VM_LOCKED) ||
- ptep_clear_flush_young(vma, address, pte)) {
+ (ptep_clear_flush_young(vma, address, pte)
+ && !ignore_refs)) {
ret = SWAP_FAIL;
goto out_unmap;
}
@@ -728,7 +730,7 @@ static void try_to_unmap_cluster(unsigne
pte_unmap_unlock(pte - 1, ptl);
}
-static int try_to_unmap_anon(struct page *page)
+static int try_to_unmap_anon(struct page *page, int ignore_refs)
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
@@ -739,7 +741,7 @@ static int try_to_unmap_anon(struct page
return ret;
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
- ret = try_to_unmap_one(page, vma);
+ ret = try_to_unmap_one(page, vma, ignore_refs);
if (ret == SWAP_FAIL || !page_mapped(page))
break;
}
@@ -756,7 +758,7 @@ static int try_to_unmap_anon(struct page
*
* This function is only called from try_to_unmap for object-based pages.
*/
-static int try_to_unmap_file(struct page *page)
+static int try_to_unmap_file(struct page *page, int ignore_refs)
{
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -770,7 +772,7 @@ 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);
+ ret = try_to_unmap_one(page, vma, ignore_refs);
if (ret == SWAP_FAIL || !page_mapped(page))
goto out;
}
@@ -855,16 +857,16 @@ out:
* SWAP_AGAIN - we missed a mapping, try again later
* SWAP_FAIL - the page is unswappable
*/
-int try_to_unmap(struct page *page)
+int try_to_unmap(struct page *page, int ignore_refs)
{
int ret;
BUG_ON(!PageLocked(page));
if (PageAnon(page))
- ret = try_to_unmap_anon(page);
+ ret = try_to_unmap_anon(page, ignore_refs);
else
- ret = try_to_unmap_file(page);
+ ret = try_to_unmap_file(page, ignore_refs);
if (!page_mapped(page))
ret = SWAP_SUCCESS;
Index: linux-2.6.15/include/linux/rmap.h
===================================================================
--- linux-2.6.15.orig/include/linux/rmap.h 2006-01-11 19:22:19.000000000 -0800
+++ linux-2.6.15/include/linux/rmap.h 2006-01-11 19:22:22.000000000 -0800
@@ -91,7 +91,7 @@ static inline void page_dup_rmap(struct
* Called from mm/vmscan.c to handle paging out
*/
int page_referenced(struct page *, int is_locked);
-int try_to_unmap(struct page *);
+int try_to_unmap(struct page *, int ignore_refs);
#ifdef CONFIG_MIGRATION
void remove_from_swap(struct page *page);
#endif
@@ -114,7 +114,7 @@ unsigned long page_address_in_vma(struct
#define anon_vma_link(vma) do {} while (0)
#define page_referenced(page,l) TestClearPageReferenced(page)
-#define try_to_unmap(page) SWAP_FAIL
+#define try_to_unmap(page, refs) SWAP_FAIL
#endif /* CONFIG_MMU */
-
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