linux-kernel - [PATCH 2/3] mm: make the threshold of enabling THP configurable

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Date:	Tue, 21 Jun 2011 00:34:29 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, Amerigo Wang <amwang@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mel@....ul.ie>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org
Subject: [PATCH 2/3] mm: make the threshold of enabling THP configurable

Don't hard-code 512M as the threshold in kernel, make it configruable,
and set 512M by default.

Signed-off-by: WANG Cong <amwang@...hat.com>
---
 mm/Kconfig       |   10 ++++++++++
 mm/huge_memory.c |    2 +-
 2 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 8ca47a5..a826471 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -340,6 +340,16 @@ choice
 	  benefit.
 endchoice
 
+config TRANSPARENT_HUGEPAGE_THRESHOLD
+	depends on TRANSPARENT_HUGEPAGE
+	int "The minimal threshold of enabling Transparent Hugepage"
+	range 512 8192
+	default "512"
+	help
+	  The threshold of enabling Transparent Huagepage automatically,
+	  in Mbytes, below this value, Transparent Hugepage will be disabled
+	  by default during boot.
+
 #
 # UP and nommu archs use km based percpu allocator
 #
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9c63c90..7fb44cc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -544,7 +544,7 @@ static int __init hugepage_init(void)
 	 * where the extra memory used could hurt more than TLB overhead
 	 * is likely to save.  The admin can still enable it through /sys.
 	 */
-	if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
+	if (totalram_pages < (CONFIG_TRANSPARENT_HUGEPAGE_THRESHOLD << (20 - PAGE_SHIFT)))
 		transparent_hugepage_flags = 0;
 
 	start_khugepaged();
-- 
1.7.4.4

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