writeback tuning

@@ -458,35 +458,20 @@ static int shrink_cache(int nr_pages, zo
 			 * pinned it and after the I/O to the page is finished,
 			 * so the direct writes to the page cannot get lost.
 			 */
-			struct address_space_operations *a_ops;
 			int (*writeback)(struct page *, int *);
-			int (*writepage)(struct page *);
+			const int nr_pages = SWAP_CLUSTER_MAX;
+			int nr_to_write = nr_pages;
 
-			/*
-			 * There's no guarantee that writeback() will actually
-			 * start I/O against *this* page.  Which is broken if we're
-			 * trying to free memory in a particular zone.  FIXME.
-			 */
-			a_ops = mapping->a_ops;
-			writeback = a_ops->vm_writeback;
-			writepage = a_ops->writepage;
-			if (writeback || writepage) {
-				SetPageLaunder(page);
-				page_cache_get(page);
-				spin_unlock(&pagemap_lru_lock);
-				ClearPageDirty(page);
-
-				if (writeback) {
-					int nr_to_write = WRITEOUT_PAGES;
-					writeback(page, &nr_to_write);
-				} else {
-					writepage(page);
-				}
-				page_cache_release(page);
-
-				spin_lock(&pagemap_lru_lock);
-				continue;
-			}
+			writeback = mapping->a_ops->vm_writeback;
+			if (writeback == NULL)
+				writeback = generic_vm_writeback;
+			page_cache_get(page);
+			spin_unlock(&pagemap_lru_lock);
+			(*writeback)(page, &nr_to_write);
+			max_scan -= (nr_pages - nr_to_write);
+			page_cache_release(page);
+			spin_lock(&pagemap_lru_lock);
+			continue;
 		}
 
 		/*

@@ -648,6 +633,8 @@ static int shrink_caches(zone_t * classz
 	if (nr_pages <= 0)
 		return 0;
 
+	wakeup_bdflush();
+
 	shrink_dcache_memory(priority, gfp_mask);
 
 	/* After shrinking the dcache, get rid of unused inodes too .. */

368 lines not on this page · raw message

@@ -46,17 +46,9 @@ static inline void wait_on_inode(struct 
 /*
  * mm/page-writeback.c
  */
-/*
- * How much data to write out at a time in various places.  This isn't
- * really very important - it's just here to prevent any thread from
- * locking an inode for too long and blocking other threads which wish
- * to write the same file for allocation throttling purposes.
- */
-#define WRITEOUT_PAGES	((4096 * 1024) / PAGE_CACHE_SIZE)
-
 void balance_dirty_pages(struct address_space *mapping);
 void balance_dirty_pages_ratelimited(struct address_space *mapping);
-int pdflush_flush(unsigned long nr_pages);
 int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);
+int writeback_mapping(struct address_space *mapping, int *nr_to_write);
 
 #endif		/* WRITEBACK_H */

@@ -2408,11 +2408,6 @@ asmlinkage long sys_bdflush(int func, lo
 	return 0;
 }
 
-void wakeup_bdflush(void)
-{
- 	pdflush_flush(0);
-}
-
 /*
  * Buffer-head allocation
  */

@@ -31,7 +31,25 @@ static int swap_writepage(struct page *p
 	return 0;
 }
 
+/*
+ * swapper_space doesn't have a real inode, so it gets a special vm_writeback()
+ * so we don't need swap special cases in generic_vm_writeback().
+ *
+ * FIXME: swap pages are locked, but not PageWriteback while under writeout.
+ * This will confuse throttling in shrink_cache().  It may be advantageous to
+ * set PG_writeback against swap pages while they're also locked.  Either that,
+ * or special-case swap pages in shrink_cache().
+ */
+static int swap_vm_writeback(struct page *page, int *nr_to_write)
+{
+	struct address_space *mapping = page->mapping;
+
+	unlock_page(page);
+	return generic_writeback_mapping(mapping, nr_to_write);
+}
+
 static struct address_space_operations swap_aops = {
+	vm_writeback: swap_vm_writeback,
 	writepage: swap_writepage,
 	sync_page: block_sync_page,
 };

@@ -453,9 +453,7 @@ EXPORT_SYMBOL(fail_writepage);
  */
 int filemap_fdatawrite(struct address_space *mapping)
 {
-	if (mapping->a_ops->writeback_mapping)
-		return mapping->a_ops->writeback_mapping(mapping, NULL);
-	return generic_writeback_mapping(mapping, NULL);
+	return writeback_mapping(mapping, NULL);
 }
 
 /**

@@ -402,14 +402,6 @@ void prune_icache(int goal)
 	spin_unlock(&inode_lock);
 
 	dispose_list(freeable);
-
-	/* 
-	 * If we didn't free enough clean inodes then schedule writeback of
-	 * the dirty inodes.  We cannot do it from here or we're either
-	 * synchronously dogslow or we deadlock with oom.
-	 */
-	if (goal)
-		pdflush_operation(try_to_writeback_unused_inodes, 0);
 }
 
 /*