[PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

[PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

[Andy Whitcroft]

As we can determine exactly when a gigantic page is in use we can optimise
the common regular page cases by pulling out gigantic page initialisation
into its own function.  As gigantic pages are never released to buddy we
do not need a destructor.  This effectivly reverts the previous change
to the main buddy allocator.  It also adds a paranoid check to ensure we
never release gigantic pages from hugetlbfs to the main buddy.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
---
 mm/hugetlb.c    |    4 +++-
 mm/internal.h   |    1 +
 mm/page_alloc.c |   26 +++++++++++++++++++-------
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bb5cf81..716b151 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -460,6 +460,8 @@ static void update_and_free_page(struct hstate *h, struct page *page)
 {
 	int i;
 
+	BUG_ON(h->order >= MAX_ORDER);
+
 	h->nr_huge_pages--;
 	h->nr_huge_pages_node[page_to_nid(page)]--;
 	for (i = 0; i < pages_per_huge_page(h); i++) {
@@ -984,7 +986,7 @@ static void __init gather_bootmem_prealloc(void)
 		struct hstate *h = m->hstate;
 		__ClearPageReserved(page);
 		WARN_ON(page_count(page) != 1);
-		prep_compound_page(page, h->order);
+		prep_compound_gigantic_page(page, h->order);
 		prep_new_huge_page(h, page, page_to_nid(page));
 	}
 }
diff --git a/mm/internal.h b/mm/internal.h
index 08b8dea..92729ea 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -17,6 +17,7 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long floor, unsigned long ceiling);
 
 extern void prep_compound_page(struct page *page, unsigned long order);
+extern void prep_compound_gigantic_page(struct page *page, unsigned long order);
 
 static inline void set_page_count(struct page *page, int v)
 {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 27b8681..dbeb3f8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -268,14 +268,28 @@ void prep_compound_page(struct page *page, unsigned long order)
 {
 	int i;
 	int nr_pages = 1 << order;
+
+	set_compound_page_dtor(page, free_compound_page);
+	set_compound_order(page, order);
+	__SetPageHead(page);
+	for (i = 1; i < nr_pages; i++) {
+		struct page *p = page + i;
+
+		__SetPageTail(p);
+		p->first_page = page;
+	}
+}
+
+void prep_compound_gigantic_page(struct page *page, unsigned long order)
+{
+	int i;
+	int nr_pages = 1 << order;
 	struct page *p = page + 1;
 
 	set_compound_page_dtor(page, free_compound_page);
 	set_compound_order(page, order);
 	__SetPageHead(page);
-	for (i = 1; i < nr_pages; i++, p++) {
-		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
-			p = pfn_to_page(page_to_pfn(page) + i);
+	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
 		__SetPageTail(p);
 		p->first_page = page;
 	}
@@ -285,7 +299,6 @@ static void destroy_compound_page(struct page *page, unsigned long order)
 {
 	int i;
 	int nr_pages = 1 << order;
-	struct page *p = page + 1;
 
 	if (unlikely(compound_order(page) != order))
 		bad_page(page);
@@ -293,9 +306,8 @@ static void destroy_compound_page(struct page *page, unsigned long order)
 	if (unlikely(!PageHead(page)))
 			bad_page(page);
 	__ClearPageHead(page);
-	for (i = 1; i < nr_pages; i++, p++) {
-		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
-			p = pfn_to_page(page_to_pfn(page) + i);
+	for (i = 1; i < nr_pages; i++) {
+		struct page *p = page + i;
 
 		if (unlikely(!PageTail(p) |
 				(p->first_page != page)))
-- 
1.6.0.1.451.gc8d31

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Re: [PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

[Nick Piggin]

On Wednesday 08 October 2008 20:34, Andy Whitcroft wrote:
> As we can determine exactly when a gigantic page is in use we can optimise
> the common regular page cases by pulling out gigantic page initialisation
> into its own function.  As gigantic pages are never released to buddy we
> do not need a destructor.  This effectivly reverts the previous change
> to the main buddy allocator.  It also adds a paranoid check to ensure we
> never release gigantic pages from hugetlbfs to the main buddy.

Thanks for doing this. Can prep_compound_gigantic_page be #ifdef HUGETLB?


> Signed-off-by: Andy Whitcroft <apw@shadowen.org>
> Cc: Nick Piggin <nickpiggin@yahoo.com.au>
> ---
>  mm/hugetlb.c    |    4 +++-
>  mm/internal.h   |    1 +
>  mm/page_alloc.c |   26 +++++++++++++++++++-------
>  3 files changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bb5cf81..716b151 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -460,6 +460,8 @@ static void update_and_free_page(struct hstate *h,
> struct page *page) {
>  	int i;
>
> +	BUG_ON(h->order >= MAX_ORDER);
> +
>  	h->nr_huge_pages--;
>  	h->nr_huge_pages_node[page_to_nid(page)]--;
>  	for (i = 0; i < pages_per_huge_page(h); i++) {
> @@ -984,7 +986,7 @@ static void __init gather_bootmem_prealloc(void)
>  		struct hstate *h = m->hstate;
>  		__ClearPageReserved(page);
>  		WARN_ON(page_count(page) != 1);
> -		prep_compound_page(page, h->order);
> +		prep_compound_gigantic_page(page, h->order);
>  		prep_new_huge_page(h, page, page_to_nid(page));
>  	}
>  }
> diff --git a/mm/internal.h b/mm/internal.h
> index 08b8dea..92729ea 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -17,6 +17,7 @@ void free_pgtables(struct mmu_gather *tlb, struct
> vm_area_struct *start_vma, unsigned long floor, unsigned long ceiling);
>
>  extern void prep_compound_page(struct page *page, unsigned long order);
> +extern void prep_compound_gigantic_page(struct page *page, unsigned long
> order);
>
>  static inline void set_page_count(struct page *page, int v)
>  {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 27b8681..dbeb3f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -268,14 +268,28 @@ void prep_compound_page(struct page *page, unsigned
> long order) {
>  	int i;
>  	int nr_pages = 1 << order;
> +
> +	set_compound_page_dtor(page, free_compound_page);
> +	set_compound_order(page, order);
> +	__SetPageHead(page);
> +	for (i = 1; i < nr_pages; i++) {
> +		struct page *p = page + i;
> +
> +		__SetPageTail(p);
> +		p->first_page = page;
> +	}
> +}
> +
> +void prep_compound_gigantic_page(struct page *page, unsigned long order)
> +{
> +	int i;
> +	int nr_pages = 1 << order;
>  	struct page *p = page + 1;
>
>  	set_compound_page_dtor(page, free_compound_page);
>  	set_compound_order(page, order);
>  	__SetPageHead(page);
> -	for (i = 1; i < nr_pages; i++, p++) {
> -		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> -			p = pfn_to_page(page_to_pfn(page) + i);
> +	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
>  		__SetPageTail(p);
>  		p->first_page = page;
>  	}
> @@ -285,7 +299,6 @@ static void destroy_compound_page(struct page *page,
> unsigned long order) {
>  	int i;
>  	int nr_pages = 1 << order;
> -	struct page *p = page + 1;
>
>  	if (unlikely(compound_order(page) != order))
>  		bad_page(page);
> @@ -293,9 +306,8 @@ static void destroy_compound_page(struct page *page,
> unsigned long order) if (unlikely(!PageHead(page)))
>  			bad_page(page);
>  	__ClearPageHead(page);
> -	for (i = 1; i < nr_pages; i++, p++) {
> -		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> -			p = pfn_to_page(page_to_pfn(page) + i);
> +	for (i = 1; i < nr_pages; i++) {
> +		struct page *p = page + i;
>
>  		if (unlikely(!PageTail(p) |
>  				(p->first_page != page)))

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Re: [PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

[Andrew Morton]

On Wed, 8 Oct 2008 23:31:45 +1100
Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> On Wednesday 08 October 2008 20:34, Andy Whitcroft wrote:
> > As we can determine exactly when a gigantic page is in use we can optimise
> > the common regular page cases by pulling out gigantic page initialisation
> > into its own function.  As gigantic pages are never released to buddy we
> > do not need a destructor.  This effectivly reverts the previous change
> > to the main buddy allocator.  It also adds a paranoid check to ensure we
> > never release gigantic pages from hugetlbfs to the main buddy.
> 
> Thanks for doing this. Can prep_compound_gigantic_page be #ifdef HUGETLB?

Yup.

--- a/mm/page_alloc.c~hugetlb-pull-gigantic-page-initialisation-out-of-the-default-path-fix
+++ a/mm/page_alloc.c
@@ -280,6 +280,7 @@ void prep_compound_page(struct page *pag
 	}
 }
 
+#ifdef CONFIG_HUGETLBFS
 void prep_compound_gigantic_page(struct page *page, unsigned long order)
 {
 	int i;
@@ -294,6 +295,7 @@ void prep_compound_gigantic_page(struct 
 		p->first_page = page;
 	}
 }
+#endif
 
 static void destroy_compound_page(struct page *page, unsigned long order)
 {
_

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Re: [PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

[Mel Gorman]

On (08/10/08 10:34), Andy Whitcroft didst pronounce:
> As we can determine exactly when a gigantic page is in use we can optimise
> the common regular page cases by pulling out gigantic page initialisation
> into its own function.  As gigantic pages are never released to buddy we
> do not need a destructor.  This effectivly reverts the previous change
> to the main buddy allocator.  It also adds a paranoid check to ensure we
> never release gigantic pages from hugetlbfs to the main buddy.
> 
> Signed-off-by: Andy Whitcroft <apw@shadowen.org>
> Cc: Nick Piggin <nickpiggin@yahoo.com.au>

Acked-by: Mel Gorman <mel@csn.ul.ie>

> ---
>  mm/hugetlb.c    |    4 +++-
>  mm/internal.h   |    1 +
>  mm/page_alloc.c |   26 +++++++++++++++++++-------
>  3 files changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bb5cf81..716b151 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -460,6 +460,8 @@ static void update_and_free_page(struct hstate *h, struct page *page)
>  {
>  	int i;
>  
> +	BUG_ON(h->order >= MAX_ORDER);
> +
>  	h->nr_huge_pages--;
>  	h->nr_huge_pages_node[page_to_nid(page)]--;
>  	for (i = 0; i < pages_per_huge_page(h); i++) {
> @@ -984,7 +986,7 @@ static void __init gather_bootmem_prealloc(void)
>  		struct hstate *h = m->hstate;
>  		__ClearPageReserved(page);
>  		WARN_ON(page_count(page) != 1);
> -		prep_compound_page(page, h->order);
> +		prep_compound_gigantic_page(page, h->order);
>  		prep_new_huge_page(h, page, page_to_nid(page));
>  	}
>  }
> diff --git a/mm/internal.h b/mm/internal.h
> index 08b8dea..92729ea 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -17,6 +17,7 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
>  		unsigned long floor, unsigned long ceiling);
>  
>  extern void prep_compound_page(struct page *page, unsigned long order);
> +extern void prep_compound_gigantic_page(struct page *page, unsigned long order);
>  
>  static inline void set_page_count(struct page *page, int v)
>  {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 27b8681..dbeb3f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -268,14 +268,28 @@ void prep_compound_page(struct page *page, unsigned long order)
>  {
>  	int i;
>  	int nr_pages = 1 << order;
> +
> +	set_compound_page_dtor(page, free_compound_page);
> +	set_compound_order(page, order);
> +	__SetPageHead(page);
> +	for (i = 1; i < nr_pages; i++) {
> +		struct page *p = page + i;
> +
> +		__SetPageTail(p);
> +		p->first_page = page;
> +	}
> +}
> +
> +void prep_compound_gigantic_page(struct page *page, unsigned long order)
> +{
> +	int i;
> +	int nr_pages = 1 << order;
>  	struct page *p = page + 1;
>  
>  	set_compound_page_dtor(page, free_compound_page);
>  	set_compound_order(page, order);
>  	__SetPageHead(page);
> -	for (i = 1; i < nr_pages; i++, p++) {
> -		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> -			p = pfn_to_page(page_to_pfn(page) + i);
> +	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
>  		__SetPageTail(p);
>  		p->first_page = page;
>  	}
> @@ -285,7 +299,6 @@ static void destroy_compound_page(struct page *page, unsigned long order)
>  {
>  	int i;
>  	int nr_pages = 1 << order;
> -	struct page *p = page + 1;
>  
>  	if (unlikely(compound_order(page) != order))
>  		bad_page(page);
> @@ -293,9 +306,8 @@ static void destroy_compound_page(struct page *page, unsigned long order)
>  	if (unlikely(!PageHead(page)))
>  			bad_page(page);
>  	__ClearPageHead(page);
> -	for (i = 1; i < nr_pages; i++, p++) {
> -		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> -			p = pfn_to_page(page_to_pfn(page) + i);
> +	for (i = 1; i < nr_pages; i++) {
> +		struct page *p = page + i;
>  
>  		if (unlikely(!PageTail(p) |
>  				(p->first_page != page)))
> -- 
> 1.6.0.1.451.gc8d31
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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