[PATCH] batched freeing of anon pages

A reworked version of the batched page freeing and lock amortisation
for VMA teardown.

It walks the existing 507-page list in the mmu_gather_t in 16-page
chunks, drops their refcounts in 16-page chunks, and de-LRUs and
frees any resulting zero-count pages in up-to-16 page chunks.

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index e629251cb7a7c33658feb70360d5256fa7671038..f3564a558be4d20a7bcf35091d9529a773e1eca9 100644 (file)
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -79,10 +79,8 @@ static inline void tlb_flush_mmu(mmu_gather_t *tlb, unsigned long start, unsigne
        tlb_flush(tlb);
        nr = tlb->nr;
        if (!tlb_fast_mode(tlb)) {
-               unsigned long i;
+               free_pages_and_swap_cache(tlb->pages, tlb->nr);
                tlb->nr = 0;
-               for (i=0; i < nr; i++)
-                       free_page_and_swap_cache(tlb->pages[i]);
        }
 }
 

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7a41a4184a27e5aec90fc0f9b50b9405e8f36c37..43390b2e2ef4f52540292f9af507d12543aafa24 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -24,6 +24,7 @@
 
 #define page_cache_get(page)           get_page(page)
 #define page_cache_release(page)       put_page(page)
+void release_pages(struct page **pages, int nr);
 
 static inline struct page *page_cache_alloc(struct address_space *x)
 {

diff --git a/include/linux/swap.h b/include/linux/swap.h
index affa89d77eb165d96f42c420fc9bf494bad1a797..8844b1408788547bfa26957f6a08e545548d7ed7 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -182,6 +182,7 @@ extern int move_to_swap_cache(struct page *page, swp_entry_t entry);
 extern int move_from_swap_cache(struct page *page, unsigned long index,
                struct address_space *mapping);
 extern void free_page_and_swap_cache(struct page *page);
+extern void free_pages_and_swap_cache(struct page **pages, int nr);
 extern struct page * lookup_swap_cache(swp_entry_t);
 extern struct page * read_swap_cache_async(swp_entry_t);
 

diff --git a/mm/swap.c b/mm/swap.c
index 848ca6aa919f6be4e36f9cbbf66a30828555b8f4..516a547d524711d15368799cd95f2a1d402e4ba6 100644 (file)
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -87,7 +87,7 @@ void __page_cache_release(struct page *page)
 
 /*
  * Batched page_cache_release().  Decrement the reference count on all the
- * pagevec's pages.  If it fell to zero then remove the page from the LRU and
+ * passed pages.  If it fell to zero then remove the page from the LRU and
  * free it.
  *
  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
@@ -96,18 +96,16 @@ void __page_cache_release(struct page *page)
  * The locking in this function is against shrink_cache(): we recheck the
  * page count inside the lock to see whether shrink_cache grabbed the page
  * via the LRU.  If it did, give up: shrink_cache will free it.
- *
- * This function reinitialises the caller's pagevec.
  */
-void __pagevec_release(struct pagevec *pvec)
+void release_pages(struct page **pages, int nr)
 {
        int i;
        struct pagevec pages_to_free;
        struct zone *zone = NULL;
 
        pagevec_init(&pages_to_free);
-       for (i = 0; i < pagevec_count(pvec); i++) {
-               struct page *page = pvec->pages[i];
+       for (i = 0; i < nr; i++) {
+               struct page *page = pages[i];
                struct zone *pagezone;
 
                if (PageReserved(page) || !put_page_testzero(page))
@@ -122,13 +120,24 @@ void __pagevec_release(struct pagevec *pvec)
                }
                if (TestClearPageLRU(page))
                        del_page_from_lru(zone, page);
-               if (page_count(page) == 0)
-                       pagevec_add(&pages_to_free, page);
+               if (page_count(page) == 0) {
+                       if (!pagevec_add(&pages_to_free, page)) {
+                               spin_unlock_irq(&zone->lru_lock);
+                               pagevec_free(&pages_to_free);
+                               pagevec_init(&pages_to_free);
+                               spin_lock_irq(&zone->lru_lock);
+                       }
+               }
        }
        if (zone)
                spin_unlock_irq(&zone->lru_lock);
 
        pagevec_free(&pages_to_free);
+}
+
+void __pagevec_release(struct pagevec *pvec)
+{
+       release_pages(pvec->pages, pagevec_count(pvec));
        pagevec_init(pvec);
 }
 

diff --git a/mm/swap_state.c b/mm/swap_state.c
index a69e81415c2be019f7e80927c3ca494e9495d78d..1edd38c388d1ba9ddafe1997ba71b91afcc9640d 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -292,28 +292,55 @@ int move_from_swap_cache(struct page *page, unsigned long index,
        return err;
 }
 
+
 /* 
- * Perform a free_page(), also freeing any swap cache associated with
- * this page if it is the last user of the page. Can not do a lock_page,
- * as we are holding the page_table_lock spinlock.
+ * If we are the only user, then try to free up the swap cache. 
+ * 
+ * Its ok to check for PageSwapCache without the page lock
+ * here because we are going to recheck again inside 
+ * exclusive_swap_page() _with_ the lock. 
+ *                                     - Marcelo
  */
-void free_page_and_swap_cache(struct page *page)
+static inline void free_swap_cache(struct page *page)
 {
-       /* 
-        * If we are the only user, then try to free up the swap cache. 
-        * 
-        * Its ok to check for PageSwapCache without the page lock
-        * here because we are going to recheck again inside 
-        * exclusive_swap_page() _with_ the lock. 
-        *                                      - Marcelo
-        */
        if (PageSwapCache(page) && !TestSetPageLocked(page)) {
                remove_exclusive_swap_page(page);
                unlock_page(page);
        }
+}
+
+/* 
+ * Perform a free_page(), also freeing any swap cache associated with
+ * this page if it is the last user of the page. Can not do a lock_page,
+ * as we are holding the page_table_lock spinlock.
+ */
+void free_page_and_swap_cache(struct page *page)
+{
+       free_swap_cache(page);
        page_cache_release(page);
 }
 
+/*
+ * Passed an array of pages, drop them all from swapcache and then release
+ * them.  They are removed from the LRU and freed if this is their last use.
+ */
+void free_pages_and_swap_cache(struct page **pages, int nr)
+{
+       const int chunk = 16;
+       struct page **pagep = pages;
+
+       while (nr) {
+               int todo = min(chunk, nr);
+               int i;
+
+               for (i = 0; i < todo; i++)
+                       free_swap_cache(pagep[i]);
+               release_pages(pagep, todo);
+               pagep += todo;
+               nr -= todo;
+       }
+}
+
 /*
  * Lookup a swap entry in the swap cache. A found page will be returned
  * unlocked and with its refcount incremented - we rely on the kernel