Re: [PATCH -v3 08/10] mm, THP: Add can_split_huge_page()

Hi, Kirill,

Thanks for your comments!

"Kirill A. Shutemov" [off-list ref] writes:

On Wed, Sep 07, 2016 at 09:46:07AM -0700, Huang, Ying wrote:

quoted

From: Huang Ying <redacted>

Separates checking whether we can split the huge page from
split_huge_page_to_list() into a function.  This will help to check that
before splitting the THP (Transparent Huge Page) really.

This will be used for delaying splitting THP during swapping out.  Where
for a THP, we will allocate a swap cluster, add the THP into the swap
cache, then split the THP.  To avoid the unnecessary operations for the
un-splittable THP, we will check that firstly.

There is no functionality change in this patch.

Cc: Andrea Arcangeli <redacted>
Cc: Kirill A. Shutemov <redacted>
Cc: Ebru Akagunduz <redacted>
Signed-off-by: "Huang, Ying" <redacted>
---
 include/linux/huge_mm.h |  6 ++++++
 mm/huge_memory.c        | 13 ++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 9b9f65d..a0073e7 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h

@@ -94,6 +94,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp,
 extern void prep_transhuge_page(struct page *page);
 extern void free_transhuge_page(struct page *page);
 
+bool can_split_huge_page(struct page *page);
 int split_huge_page_to_list(struct page *page, struct list_head *list);
 static inline int split_huge_page(struct page *page)
 {

@@ -176,6 +177,11 @@ static inline void prep_transhuge_page(struct page *page) {}
 
 #define thp_get_unmapped_area	NULL
 
+static inline bool
+can_split_huge_page(struct page *page)
+{

BUILD_BUG() should be appropriate here.

Yes.  Will add it.

quoted

+	return false;
+}

Best Regards,
Huang, Ying

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