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

From: Amerigo Wang
Date: Mon Jun 20 2011 - 12:35:56 EST


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

Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
---
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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