PM / Hibernate: Avoid hitting OOM during preallocation of memory

There is a problem in hibernate_preallocate_memory() that it calls
preallocate_image_memory() with an argument that may be greater than
the total number of available non-highmem memory pages.  If that's
the case, the OOM condition is guaranteed to trigger, which in turn
can cause significant slowdown to occur during hibernation.

To avoid that, make preallocate_image_memory() adjust its argument
before calling preallocate_image_pages(), so that the total number of
saveable non-highem pages left is not less than the minimum size of
a hibernation image.  Change hibernate_preallocate_memory() to try to
allocate from highmem if the number of pages allocated by
preallocate_image_memory() is too low.

Modify free_unnecessary_pages() to take all possible memory
allocation patterns into account.

Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: M. Vefa Bicakci <bicave@superonline.com>

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 5e7edfb05e66cff0d2c99d5fc8fddfde03e372c3..5209b39e69822d86cf3924f5f7aa47b263f71d17 100644 (file)
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1122,9 +1122,19 @@ static unsigned long preallocate_image_pages(unsigned long nr_pages, gfp_t mask)
        return nr_alloc;
 }
 
-static unsigned long preallocate_image_memory(unsigned long nr_pages)
+static unsigned long preallocate_image_memory(unsigned long nr_pages,
+                                             unsigned long avail_normal)
 {
-       return preallocate_image_pages(nr_pages, GFP_IMAGE);
+       unsigned long alloc;
+
+       if (avail_normal <= alloc_normal)
+               return 0;
+
+       alloc = avail_normal - alloc_normal;
+       if (nr_pages < alloc)
+               alloc = nr_pages;
+
+       return preallocate_image_pages(alloc, GFP_IMAGE);
 }
 
 #ifdef CONFIG_HIGHMEM
@@ -1170,15 +1180,22 @@ static inline unsigned long preallocate_highmem_fraction(unsigned long nr_pages,
  */
 static void free_unnecessary_pages(void)
 {
-       unsigned long save_highmem, to_free_normal, to_free_highmem;
+       unsigned long save, to_free_normal, to_free_highmem;
 
-       to_free_normal = alloc_normal - count_data_pages();
-       save_highmem = count_highmem_pages();
-       if (alloc_highmem > save_highmem) {
-               to_free_highmem = alloc_highmem - save_highmem;
+       save = count_data_pages();
+       if (alloc_normal >= save) {
+               to_free_normal = alloc_normal - save;
+               save = 0;
+       } else {
+               to_free_normal = 0;
+               save -= alloc_normal;
+       }
+       save += count_highmem_pages();
+       if (alloc_highmem >= save) {
+               to_free_highmem = alloc_highmem - save;
        } else {
                to_free_highmem = 0;
-               to_free_normal -= save_highmem - alloc_highmem;
+               to_free_normal -= save - alloc_highmem;
        }
 
        memory_bm_position_reset(&copy_bm);
@@ -1259,7 +1276,7 @@ int hibernate_preallocate_memory(void)
 {
        struct zone *zone;
        unsigned long saveable, size, max_size, count, highmem, pages = 0;
-       unsigned long alloc, save_highmem, pages_highmem;
+       unsigned long alloc, save_highmem, pages_highmem, avail_normal;
        struct timeval start, stop;
        int error;
 
@@ -1296,6 +1313,7 @@ int hibernate_preallocate_memory(void)
                else
                        count += zone_page_state(zone, NR_FREE_PAGES);
        }
+       avail_normal = count;
        count += highmem;
        count -= totalreserve_pages;
 
@@ -1310,12 +1328,21 @@ int hibernate_preallocate_memory(void)
         */
        if (size >= saveable) {
                pages = preallocate_image_highmem(save_highmem);
-               pages += preallocate_image_memory(saveable - pages);
+               pages += preallocate_image_memory(saveable - pages, avail_normal);
                goto out;
        }
 
        /* Estimate the minimum size of the image. */
        pages = minimum_image_size(saveable);
+       /*
+        * To avoid excessive pressure on the normal zone, leave room in it to
+        * accommodate an image of the minimum size (unless it's already too
+        * small, in which case don't preallocate pages from it at all).
+        */
+       if (avail_normal > pages)
+               avail_normal -= pages;
+       else
+               avail_normal = 0;
        if (size < pages)
                size = min_t(unsigned long, pages, max_size);
 
@@ -1336,16 +1363,34 @@ int hibernate_preallocate_memory(void)
         */
        pages_highmem = preallocate_image_highmem(highmem / 2);
        alloc = (count - max_size) - pages_highmem;
-       pages = preallocate_image_memory(alloc);
-       if (pages < alloc)
-               goto err_out;
-       size = max_size - size;
-       alloc = size;
-       size = preallocate_highmem_fraction(size, highmem, count);
-       pages_highmem += size;
-       alloc -= size;
-       pages += preallocate_image_memory(alloc);
-       pages += pages_highmem;
+       pages = preallocate_image_memory(alloc, avail_normal);
+       if (pages < alloc) {
+               /* We have exhausted non-highmem pages, try highmem. */
+               alloc -= pages;
+               pages += pages_highmem;
+               pages_highmem = preallocate_image_highmem(alloc);
+               if (pages_highmem < alloc)
+                       goto err_out;
+               pages += pages_highmem;
+               /*
+                * size is the desired number of saveable pages to leave in
+                * memory, so try to preallocate (all memory - size) pages.
+                */
+               alloc = (count - pages) - size;
+               pages += preallocate_image_highmem(alloc);
+       } else {
+               /*
+                * There are approximately max_size saveable pages at this point
+                * and we want to reduce this number down to size.
+                */
+               alloc = max_size - size;
+               size = preallocate_highmem_fraction(alloc, highmem, count);
+               pages_highmem += size;
+               alloc -= size;
+               size = preallocate_image_memory(alloc, avail_normal);
+               pages_highmem += preallocate_image_highmem(alloc - size);
+               pages += pages_highmem + size;
+       }
 
        /*
         * We only need as many page frames for the image as there are saveable