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Subject[PATCH 51 of 66] set recommended min free kbytes
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From: Andrea Arcangeli <aarcange@redhat.com>

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>
---
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
--- 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 = HPAGE_PMD_NR * 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 += HPAGE_PMD_NR * nr_zones * 3 * 3;
+
+ /* 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 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;
}

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