thp: set recommended min free kbytes

If transparent hugepage is enabled initialize min_free_kbytes to an
optimal value by default.  This moves the hugeadm algorithm in kernel.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 7b55fe0e998b1c2e32f6bc3abf31561ab76ea36b..4ed97a2a115f5c2fa5746ae5b43878f3191796d3 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -85,6 +85,47 @@ struct khugepaged_scan {
        .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 };
 
+
+static int set_recommended_min_free_kbytes(void)
+{
+       struct zone *zone;
+       int nr_zones = 0;
+       unsigned long recommended_min;
+       extern int min_free_kbytes;
+
+       if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
+                     &transparent_hugepage_flags) &&
+           !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
+                     &transparent_hugepage_flags))
+               return 0;
+
+       for_each_populated_zone(zone)
+               nr_zones++;
+
+       /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
+       recommended_min = pageblock_nr_pages * nr_zones * 2;
+
+       /*
+        * Make sure that on average at least two pageblocks are almost free
+        * of another type, one for a migratetype to fall back to and a
+        * second to avoid subsequent fallbacks of other types There are 3
+        * MIGRATE_TYPES we care about.
+        */
+       recommended_min += pageblock_nr_pages * nr_zones *
+                          MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
+
+       /* don't ever allow to reserve more than 5% of the lowmem */
+       recommended_min = min(recommended_min,
+                             (unsigned long) nr_free_buffer_pages() / 20);
+       recommended_min <<= (PAGE_SHIFT-10);
+
+       if (recommended_min > min_free_kbytes)
+               min_free_kbytes = recommended_min;
+       setup_per_zone_wmarks();
+       return 0;
+}
+late_initcall(set_recommended_min_free_kbytes);
+
 static int start_khugepaged(void)
 {
        int err = 0;
@@ -108,6 +149,8 @@ static int start_khugepaged(void)
                mutex_unlock(&khugepaged_mutex);
                if (wakeup)
                        wake_up_interruptible(&khugepaged_wait);
+
+               set_recommended_min_free_kbytes();
        } else
                /* wakeup to exit */
                wake_up_interruptible(&khugepaged_wait);
@@ -177,6 +220,13 @@ static ssize_t enabled_store(struct kobject *kobj,
                        ret = err;
        }
 
+       if (ret > 0 &&
+           (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
+                     &transparent_hugepage_flags) ||
+            test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
+                     &transparent_hugepage_flags)))
+               set_recommended_min_free_kbytes();
+
        return ret;
 }
 static struct kobj_attribute enabled_attr =
@@ -464,6 +514,8 @@ static int __init hugepage_init(void)
 
        start_khugepaged();
 
+       set_recommended_min_free_kbytes();
+
 out:
        return err;
 }