[PATCH] mm: show message when raising min_free_kbytes in THP

[Han Pingtian]

min_free_kbytes may be raised during THP's initialization. Sometimes,
this will change the value being set by user. Showing message will
clarify this confusion.

Only show this message when changing the value set by user according to
Michal Hocko's suggestion.

Showing the old value of min_free_kbytes according to Dave Hansen's
suggestion. This will give user the chance to restore old value of
min_free_kbytes.

Signed-off-by: Han Pingtian <hanpt@xxxxxxxxxxxxxxxxxx>
---
 mm/huge_memory.c |    9 ++++++++-
 mm/page_alloc.c  |    2 +-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 7de1bf8..e0e4e29 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -100,6 +100,7 @@ static struct khugepaged_scan khugepaged_scan = {
 	.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 };
 
+extern int user_min_free_kbytes;
 
 static int set_recommended_min_free_kbytes(void)
 {
@@ -130,8 +131,14 @@ static int set_recommended_min_free_kbytes(void)
 			      (unsigned long) nr_free_buffer_pages() / 20);
 	recommended_min <<= (PAGE_SHIFT-10);
 
-	if (recommended_min > min_free_kbytes)
+	if (recommended_min > min_free_kbytes) {
+		if (user_min_free_kbytes >= 0)
+			pr_info("raising min_free_kbytes from %d to %lu "
+				"to help transparent hugepage allocations\n",
+				min_free_kbytes, recommended_min);
+
 		min_free_kbytes = recommended_min;
+	}
 	setup_per_zone_wmarks();
 	return 0;
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9ea62b2..a9dcfd8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -205,7 +205,7 @@ static char * const zone_names[MAX_NR_ZONES] = {
 };
 
 int min_free_kbytes = 1024;
-int user_min_free_kbytes;
+int user_min_free_kbytes = -1;
 
 static unsigned long __meminitdata nr_kernel_pages;
 static unsigned long __meminitdata nr_all_pages;
-- 
1.7.7.6

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