pfn_valid_within() HOLES_WITHIN_ZONES helper

PATCH In review Andy Whitcroft 4 participants 7 messages Mar 21, 2007 1 message not in the archive

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Memory management MM core Page allocator MGLRU +1 more subsystems

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Andy Whitcroft

author

2007-03-21 19:15 UTC #1 lore raw

cover pfn_valid_within() HOLES_WITHIN_ZONES helper

The thought of having a helper for the holes within zones code has come up on two different threads in the last couple of days. So I took the pfn_valid_within() patch I had developed for the linear reclaim series and pulled it forward to 2.6.21-rc4-mm1. I have split it into a three patch series to better align with the affected patch sets within -mm.

add-pfn_valid_within-helper-for-sub-MAX_ORDER-hole-detection --
adds the base helper and utilises it within the buddy allocator,

anti-fragmentation-switch-over-to-pfn_valid_within() -- changes
references within Mel Gormans anti-fragmentation patch series, and

lumpy-move-to-using-pfn_valid_within() -- changes references with
my lumpy reclaim patch series.

-apw

Andy Whitcroft

author

2007-03-21 19:15 UTC #2 lore raw

PATCH 1/3 add pfn_valid_within helper for sub-MAX_ORDER hole detection

Generally we work under the assumption that memory the mem_map array is contigious and valid out to MAX_ORDER_NR_PAGES block of pages, ie. that if we have validated any page within this MAX_ORDER_NR_PAGES block we need not check any other. This is not true when CONFIG_HOLES_IN_ZONE is set and we must check each and every reference we make from a pfn.

Add a pfn_valid_within() helper which should be used when scanning pages within a MAX_ORDER_NR_PAGES block when we have already checked the validility of the block normally with pfn_valid(). This can then be optimised away when we do not have holes within a MAX_ORDER_NR_PAGES block of pages.

Signed-off-by Andy Whitcroft <[email protected]>

Acked-by Mel Gorman <[email protected]>

---

include/linux/mmzone.h +12 -0

index 7206c77..8c87d79 100644
@@ -837,6 +837,18 @@ void sparse_init(void);
 void memory_present(int nid, unsigned long start, unsigned long end);
 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
 
+/*
+ * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
+ * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
+ * pfn_valid_within() should be used in this case; we optimise this away
+ * when we have no holes within a MAX_ORDER_NR_PAGES block.
+ */
+#ifdef CONFIG_HOLES_IN_ZONE
+#define pfn_valid_within(pfn) pfn_valid(pfn)
+#else
+#define pfn_valid_within(pfn) (1)
+#endif
+
 #endif /* !__ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MMZONE_H */

mm/page_alloc.c +2 -6

index 3d7a9e2..695b5a6 100644
@@ -206,10 +206,8 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 
 static int page_is_consistent(struct zone *zone, struct page *page)
 {
-#ifdef CONFIG_HOLES_IN_ZONE
-	if (!pfn_valid(page_to_pfn(page)))
+	if (!pfn_valid_within(page_to_pfn(page)))
 		return 0;
-#endif
 	if (zone != page_zone(page))
 		return 0;

@@ -411,10 +409,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
 static inline int page_is_buddy(struct page *page, struct page *buddy,
 								int order)
 {
-#ifdef CONFIG_HOLES_IN_ZONE
-	if (!pfn_valid(page_to_pfn(buddy)))
+	if (!pfn_valid_within(page_to_pfn(buddy)))
 		return 0;
-#endif
 
 	if (page_zone_id(page) != page_zone_id(buddy))
 		return 0;

Nick Piggin

2007-03-21 23:23 UTC #3 lore raw

Re: [PATCH 1/3] add pfn_valid_within helper for sub-MAX_ORDER hole detection

Quoted 7 lines · Andy Whitcroft

Generally we work under the assumption that memory the mem_map array is contigious and valid out to MAX_ORDER_NR_PAGES block of pages, ie. that if we have validated any page within this MAX_ORDER_NR_PAGES block we need not check any other. This is not true when CONFIG_HOLES_IN_ZONE is set and we must check each and every reference we make from a pfn.

Quoted 5 lines

Add a pfn_valid_within() helper which should be used when scanning pages within a MAX_ORDER_NR_PAGES block when we have already checked the validility of the block normally with pfn_valid(). This can then be optimised away when we do not have holes within a MAX_ORDER_NR_PAGES block of pages.

Nice cleanup. Horrible name ;) Calls read like "is the pfn valid within pfn".

I can't think of anything really good, but I think, say, pfn_valid_within_block or pfn_valid_within_valid_block would be a bit better. You still get a slight net savings in keystrokes!

Thanks,
Nick

Quoted 61 lines

Signed-off-by Andy Whitcroft <[email protected]>

Acked-by Mel Gorman <[email protected]>

---

include/linux/mmzone.h +12 -0

index 7206c77..8c87d79 100644
@@ -837,6 +837,18 @@ void sparse_init(void);
 void memory_present(int nid, unsigned long start, unsigned long end);
 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
 
+/*
+ * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
+ * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
+ * pfn_valid_within() should be used in this case; we optimise this away
+ * when we have no holes within a MAX_ORDER_NR_PAGES block.
+ */
+#ifdef CONFIG_HOLES_IN_ZONE
+#define pfn_valid_within(pfn) pfn_valid(pfn)
+#else
+#define pfn_valid_within(pfn) (1)
+#endif
+
 #endif /* !__ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MMZONE_H */

mm/page_alloc.c +2 -7

index 3d7a9e2..695b5a6 100644
@@ -206,10 +206,8 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 
 static int page_is_consistent(struct zone *zone, struct page *page)
 {
-#ifdef CONFIG_HOLES_IN_ZONE
-	if (!pfn_valid(page_to_pfn(page)))
+	if (!pfn_valid_within(page_to_pfn(page)))
 		return 0;
-#endif
 	if (zone != page_zone(page))
 		return 0;

@@ -411,10 +409,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
 static inline int page_is_buddy(struct page *page, struct page *buddy,
 								int order)
 {
-#ifdef CONFIG_HOLES_IN_ZONE
-	if (!pfn_valid(page_to_pfn(buddy)))
+	if (!pfn_valid_within(page_to_pfn(buddy)))
 		return 0;
-#endif
 
 	if (page_zone_id(page) != page_zone_id(buddy))
 		return 0;
-

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Andrew Morton

maintainer

2007-03-21 23:46 UTC #4 lore raw

Re: [PATCH 1/3] add pfn_valid_within helper for sub-MAX_ORDER hole detection

Quoted 8 lines · On Thu, 22 Mar 2007 10:23:27 +1100 Nick Piggin <[email protected]> wrote:

Quoted 7 lines · Andy Whitcroft
Generally we work under the assumption that memory the mem_map array is contigious and valid out to MAX_ORDER_NR_PAGES block of pages, ie. that if we have validated any page within this MAX_ORDER_NR_PAGES block we need not check any other. This is not true when CONFIG_HOLES_IN_ZONE is set and we must check each and every reference we make from a pfn.

Quoted 8 lines

Quoted 5 lines
Add a pfn_valid_within() helper which should be used when scanning pages within a MAX_ORDER_NR_PAGES block when we have already checked the validility of the block normally with pfn_valid(). This can then be optimised away when we do not have holes within a MAX_ORDER_NR_PAGES block of pages.
Nice cleanup. Horrible name ;) Calls read like "is the pfn valid within pfn".

yeah

Quoted 3 lines

I can't think of anything really good, but I think, say, pfn_valid_within_block or pfn_valid_within_valid_block would be a bit better. You still get a slight net savings in keystrokes!

Neither of those identifiers seem to really fit, and I can't think of anything suitable either. Oh well, at least pfn_valid_within() has a nice comment explaining what it does.

Andy Whitcroft

author

2007-03-21 19:16 UTC #5 lore raw

PATCH 2/3 anti-fragmentation: switch over to pfn_valid_within()

In reply to Andy Whitcroft

Move to using pfn_valid_within().

Signed-off-by Andy Whitcroft <[email protected]>

Acked-by Mel Gorman <[email protected]>

---

mm/page_alloc.c +1 -3

index 695b5a6..3d7c29e 100644
@@ -747,12 +747,10 @@ int move_freepages(struct zone *zone,
 #endif
 
 	for (page = start_page; page < end_page;) {
-#ifdef CONFIG_HOLES_IN_ZONE
-		if (!pfn_valid(page_to_pfn(page))) {
+		if (!pfn_valid_within(page_to_pfn(page))) {
 			page++;
 			continue;
 		}
-#endif
 
 		if (!PageBuddy(page)) {
 			page++;

Andy Whitcroft

author

2007-03-21 19:16 UTC #6 lore raw

PATCH 3/3 lumpy: move to using pfn_valid_within()

In reply to Andy Whitcroft

Switch to using pfn_valid_within() in lumpy reclaim.

Signed-off-by Andy Whitcroft <[email protected]>

Acked-by Mel Gorman <[email protected]>

---

mm/vmscan.c +2 -3

index c3dc544..cf55c57 100644
@@ -722,11 +722,10 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 			/* The target page is in the block, ignore it. */
 			if (unlikely(pfn == page_pfn))
 				continue;
-#ifdef CONFIG_HOLES_IN_ZONE
+
 			/* Avoid holes within the zone. */
-			if (unlikely(!pfn_valid(pfn)))
+			if (unlikely(!pfn_valid_within(pfn)))
 				break;
-#endif
 
 			cursor_page = pfn_to_page(pfn);
 			/* Check that we have not crossed a zone boundary. */

Bob Picco

Acked-by on the v1 series

2007-03-21 20:27 UTC #7 lore raw

In reply to Andy Whitcroft

Andy Wihitcroft wrote: [Wed Mar 21 2007, 02:14:55PM EST]

Quoted 10 lines

The thought of having a helper for the holes within zones code has come up on two different threads in the last couple of days. So I took the pfn_valid_within() patch I had developed for the linear reclaim series and pulled it forward to 2.6.21-rc4-mm1. I have split it into a three patch series to better align with the affected patch sets within -mm.
add-pfn_valid_within-helper-for-sub-MAX_ORDER-hole-detection --
adds the base helper and utilises it within the buddy allocator,

Quoted 7 lines

anti-fragmentation-switch-over-to-pfn_valid_within() -- changes
references within Mel Gormans anti-fragmentation patch series, and
lumpy-move-to-using-pfn_valid_within() -- changes references with
my lumpy reclaim patch series.
-apw

Andy,

Thanks for doing this.

Acked-by Bob Picco <[email protected]>