[PATCH] add kswapd success accounting to /proc/vmstat

Tells us how many pages were reclaimed by kswapd.

The `pgsteal' statistic tells us how many pages were reclaimed
altogether.  So

	kswapd_steal - pgsteal

is the number of pages which were directly reclaimed by page allocating
processes.


Also, the `pgscan' data is currently counting the number of pages
scanned in shrink_cache() plus the number of pages scanned in
refill_inactive_zone().  These are rather separate concepts, so I
created the new `pgrefill' counter for refill_inactive_zone().
`pgscan' is now just the number of pages scanned in shrink_cache().

include/linux/page-flags.h

@@ -98,7 +98,9 @@ extern struct page_state {
 	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;
 } ____cacheline_aligned_in_smp page_states[NR_CPUS];

include/linux/sched.h

@@ -433,6 +433,7 @@ do { if (atomic_dec_and_test(&(tsk)->usage)) __put_task_struct(tsk); } while(0)
 #define PF_FROZEN	0x00040000	/* frozen for system suspend */
 #define PF_SYNC		0x00080000	/* performing fsync(), etc */
 #define PF_FSTRANS	0x00100000	/* inside a filesystem transaction */
+#define PF_KSWAPD	0x00200000	/* I am kswapd */
 
 /*
  * Ptrace flags

mm/page_alloc.c

@@ -1080,7 +1080,9 @@ static char *vmstat_text[] = {
 	"pgfault",
 	"pgmajfault",
 	"pgscan",
+	"pgrefill",
 	"pgsteal",
+	"kswapd_steal",
 	"pageoutrun",
 	"allocstall",
 };

mm/vmscan.c

@@ -313,6 +313,8 @@ shrink_list(struct list_head *page_list, int nr_pages,
 	if (pagevec_count(&freed_pvec))
 		__pagevec_release_nonlru(&freed_pvec);
 	mod_page_state(pgsteal, nr_pages_in - nr_pages);
+	if (current->flags & PF_KSWAPD)
+		mod_page_state(kswapd_steal, nr_pages_in - nr_pages);
 	mod_page_state(pgactivate, pgactivate);
 	return nr_pages;
 }
@@ -527,7 +529,7 @@ refill_inactive_zone(struct zone *zone, const int nr_pages_in)
 	spin_unlock_irq(&zone->lru_lock);
 	pagevec_release(&pvec);
 
-	mod_page_state(pgscan, nr_pages_in - nr_pages);
+	mod_page_state(pgrefill, nr_pages_in - nr_pages);
 	mod_page_state(pgdeactivate, pgdeactivate);
 }
 
@@ -757,7 +759,7 @@ int kswapd(void *p)
 	 * us from recursively trying to free more memory as we're
 	 * trying to free the first piece of memory in the first place).
 	 */
-	tsk->flags |= PF_MEMALLOC;
+	tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
 
 	/*
 	 * Kswapd main loop.