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SubjectRe: [RFC] Tracking mlocked pages and moving them off the LRU
Patch seems to work and survives AIM7. However, we only know about 30% of 
the Mlocked pages after boot. With this additional patch to
opportunistically move pages off the LRU immediately I can get the counter
be accurate (for all practical purposes) like the non lazy version:


Index: current/mm/memory.c
===================================================================
--- current.orig/mm/memory.c 2007-02-05 10:44:10.000000000 -0800
+++ current/mm/memory.c 2007-02-05 11:01:46.000000000 -0800
@@ -919,6 +919,30 @@ void anon_add(struct vm_area_struct *vma
}

/*
+ * Opportunistically move the page off the LRU
+ * if possible. If we do not succeed then the LRU
+ * scans will take the page off.
+ */
+void try_to_set_mlocked(struct page *page)
+{
+ struct zone *zone;
+ unsigned long flags;
+
+ if (!PageLRU(page) || PageMlocked(page))
+ return;
+
+ zone = page_zone(page);
+ if (spin_trylock_irqsave(&zone->lru_lock, flags)) {
+ if (PageLRU(page) && !PageMlocked(page)) {
+ ClearPageLRU(page);
+ list_del(&page->lru);
+ SetPageMlocked(page);
+ __inc_zone_page_state(page, NR_MLOCK);
+ }
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
+ }
+}
+/*
* Do a quick page-table lookup for a single page.
*/
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
@@ -978,6 +1002,8 @@ struct page *follow_page(struct vm_area_
set_page_dirty(page);
mark_page_accessed(page);
}
+ if (vma->vm_flags & VM_LOCKED)
+ try_to_set_mlocked(page);
unlock:
pte_unmap_unlock(ptep, ptl);
out:
@@ -2271,6 +2297,8 @@ retry:
else {
inc_mm_counter(mm, file_rss);
page_add_file_rmap(new_page);
+ if (vma->vm_flags & VM_LOCKED)
+ try_to_set_mlocked(new_page);
if (write_access) {
dirty_page = new_page;
get_page(dirty_page);
-
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