[PATCH] swsusp: limit image size

Limit the size of the suspend image to approx.  500 MB, which should
improve the overall performance of swsusp on systems with more than 1 GB of
RAM.

It introduces the constant IMAGE_SIZE that can be set to the preferred size
of the image (in MB) and modifies the memory-shrinking part of swsusp to
take this constant into account (500 is the default value of IMAGE_SIZE).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/power/power.h

@@ -53,12 +53,10 @@ extern unsigned int nr_copy_pages;
 extern struct pbe *pagedir_nosave;
 
 /*
- * This compilation switch determines the way in which memory will be freed
- * during suspend.  If defined, only as much memory will be freed as needed
- * to complete the suspend, which will make it go faster.  Otherwise, the
- * largest possible amount of memory will be freed.
+ * Preferred image size in MB (set it to zero to get the smallest
+ * image possible)
  */
-#define FAST_FREE	1
+#define IMAGE_SIZE	500
 
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);

kernel/power/swsusp.c

@@ -626,7 +626,7 @@ int swsusp_write(struct pbe *pblist, unsigned int nr_pages)
 
 int swsusp_shrink_memory(void)
 {
-	long tmp;
+	long size, tmp;
 	struct zone *zone;
 	unsigned long pages = 0;
 	unsigned int i = 0;
@@ -634,11 +634,11 @@ int swsusp_shrink_memory(void)
 
 	printk("Shrinking memory...  ");
 	do {
-#ifdef FAST_FREE
-		tmp = 2 * count_highmem_pages();
-		tmp += tmp / 50 + count_data_pages();
-		tmp += (tmp + PBES_PER_PAGE - 1) / PBES_PER_PAGE +
+		size = 2 * count_highmem_pages();
+		size += size / 50 + count_data_pages();
+		size += (size + PBES_PER_PAGE - 1) / PBES_PER_PAGE +
 			PAGES_FOR_IO;
+		tmp = size;
 		for_each_zone (zone)
 			if (!is_highmem(zone))
 				tmp -= zone->free_pages;
@@ -647,11 +647,10 @@ int swsusp_shrink_memory(void)
 			if (!tmp)
 				return -ENOMEM;
 			pages += tmp;
+		} else if (size > (IMAGE_SIZE * 1024 * 1024) / PAGE_SIZE) {
+			tmp = shrink_all_memory(SHRINK_BITE);
+			pages += tmp;
 		}
-#else
-		tmp = shrink_all_memory(SHRINK_BITE);
-		pages += tmp;
-#endif
 		printk("\b%c", p[i++%4]);
 	} while (tmp > 0);
 	printk("\bdone (%lu pages freed)\n", pages);