[PATCH] vm accounting fixes and addition

- /proc/vmstat:pageoutrun and /proc/vmstat:allocstall are always
  identical.  Rework this so that

  - "allocstall" is the number of times a page allocator ran diect reclaim

  - "pageoutrun" is the number of times kswapd ran page reclaim

- Add a new stat: "pgrotated".  The number of pages which were
  rotated to the tail of the LRU for immediate reclaim by
  rotate_reclaimable_page().

- Document things a bit.

include/linux/page-flags.h

@@ -79,35 +79,36 @@
  * allowed.
  */
 struct page_state {
-	unsigned long nr_dirty;
-	unsigned long nr_writeback;
-	unsigned long nr_pagecache;
-	unsigned long nr_page_table_pages;
-	unsigned long nr_reverse_maps;
-	unsigned long nr_mapped;
-	unsigned long nr_slab;
+	unsigned long nr_dirty;		/* Dirty writeable pages */
+	unsigned long nr_writeback;	/* Pages under writeback */
+	unsigned long nr_pagecache;	/* Pages in pagecache */
+	unsigned long nr_page_table_pages;/* Pages used for pagetables */
+	unsigned long nr_reverse_maps;	/* includes PageDirect */
+	unsigned long nr_mapped;	/* mapped into pagetables */
+	unsigned long nr_slab;		/* In slab */
 #define GET_PAGE_STATE_LAST nr_slab
 
 	/*
 	 * The below are zeroed by get_page_state().  Use get_full_page_state()
 	 * to add up all these.
 	 */
-	unsigned long pgpgin;
-	unsigned long pgpgout;
-	unsigned long pswpin;
-	unsigned long pswpout;
-	unsigned long pgalloc;
-	unsigned long pgfree;
-	unsigned long pgactivate;
-	unsigned long pgdeactivate;
-	unsigned long pgfault;
-	unsigned long pgmajfault;
-	unsigned long pgscan;
-	unsigned long pgrefill;
-	unsigned long pgsteal;
-	unsigned long kswapd_steal;
-	unsigned long pageoutrun;
-	unsigned long allocstall;
+	unsigned long pgpgin;		/* Disk reads */
+	unsigned long pgpgout;		/* Disk writes */
+	unsigned long pswpin;		/* swap reads */
+	unsigned long pswpout;		/* swap writes */
+	unsigned long pgalloc;		/* page allocations */
+	unsigned long pgfree;		/* page freeings */
+	unsigned long pgactivate;	/* pages moved inactive->active */
+	unsigned long pgdeactivate;	/* pages moved active->inactive */
+	unsigned long pgfault;		/* faults (major+minor) */
+	unsigned long pgmajfault;	/* faults (major only) */
+	unsigned long pgscan;		/* pages scanned by page reclaim */
+	unsigned long pgrefill;		/* inspected in refill_inactive_zone */
+	unsigned long pgsteal;		/* total pages reclaimed */
+	unsigned long kswapd_steal;	/* pages reclaimed by kswapd */
+	unsigned long pageoutrun;	/* kswapd's calls to page reclaim */
+	unsigned long allocstall;	/* direct reclaim calls */
+	unsigned long pgrotated;	/* pages rotated to tail of the LRU */
 } ____cacheline_aligned;
 
 DECLARE_PER_CPU(struct page_state, page_states);

mm/page_alloc.c

@@ -513,7 +513,6 @@ __alloc_pages(unsigned int gfp_mask, unsigned int order,
 	if (!wait)
 		goto nopage;
 
-	inc_page_state(allocstall);
 	current->flags |= PF_MEMALLOC;
 	try_to_free_pages(classzone, gfp_mask, order);
 	current->flags &= ~PF_MEMALLOC;
@@ -1354,6 +1353,7 @@ static char *vmstat_text[] = {
 	"kswapd_steal",
 	"pageoutrun",
 	"allocstall",
+	"pgrotated",
 };
 
 static void *vmstat_start(struct seq_file *m, loff_t *pos)

mm/swap.c

@@ -61,6 +61,7 @@ int rotate_reclaimable_page(struct page *page)
 	if (PageLRU(page) && !PageActive(page)) {
 		list_del(&page->lru);
 		list_add_tail(&page->lru, &zone->inactive_list);
+		inc_page_state(pgrotated);
 	}
 	if (!TestClearPageWriteback(page))
 		BUG();

mm/vmscan.c

@@ -797,7 +797,7 @@ try_to_free_pages(struct zone *classzone,
 	const int nr_pages = SWAP_CLUSTER_MAX;
 	int nr_reclaimed = 0;
 
-	inc_page_state(pageoutrun);
+	inc_page_state(allocstall);
 
 	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
 		int total_scanned = 0;
@@ -853,6 +853,8 @@ static int balance_pgdat(pg_data_t *pgdat, int nr_pages, struct page_state *ps)
 	int priority;
 	int i;
 
+	inc_page_state(pageoutrun);
+
 	for (priority = DEF_PRIORITY; priority; priority--) {
 		int all_zones_ok = 1;