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Subject[RFC][PATCH 1/3] contigous big page allocator

No big change since the previous version but divided into 3 patches.
This patch is based onto mmotm-1008 and just works, IOW, mot tested in
very-bad-situation.

What this wants to do:
allocates a contiguous chunk of pages larger than MAX_ORDER.
for device drivers (camera? etc..)
My intention is not for allocating HUGEPAGE(> MAX_ORDER).

What this does:
allocates a contiguous chunk of page with page migration,
based on memory hotplug codes. (memory unplug is for isolating
a chunk of page from buddy allocator.)

Consideration:
Maybe more codes can be shared with other functions
(memory hotplug, compaction..)

Status:
Maybe still needs more updates, works on small test.
[1/3] ... move some codes from memory hotplug. (no functional changes)
[2/3] ... a code for searching contiguous pages.
[3/3] ... a code for allocating contig memory.

Thanks,
-Kame
==

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Memory hotplug is a logic for making pages unused in the specified range
of pfn. So, some of core logics can be used for other purpose as
allocating a very large contigous memory block.

This patch moves some functions from mm/memory_hotplug.c to
mm/page_isolation.c. This helps adding a function for large-alloc in
page_isolation.c with memory-unplug technique.


Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
include/linux/page-isolation.h | 7 ++
mm/memory_hotplug.c | 109 ---------------------------------------
mm/page_isolation.c | 114 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 121 insertions(+), 109 deletions(-)
Index: mmotm-1008/include/linux/page-isolation.h
===================================================================
--- mmotm-1008.orig/include/linux/page-isolation.h
+++ mmotm-1008/include/linux/page-isolation.h
@@ -33,5 +33,12 @@ test_pages_isolated(unsigned long start_
extern int set_migratetype_isolate(struct page *page);
extern void unset_migratetype_isolate(struct page *page);

+/*
+ * For migration.
+ */
+
+int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn);
+int scan_lru_pages(unsigned long start, unsigned long end);
+int do_migrate_range(unsigned long start_pfn, unsigned long end_pfn);

#endif
Index: mmotm-1008/mm/memory_hotplug.c
===================================================================
--- mmotm-1008.orig/mm/memory_hotplug.c
+++ mmotm-1008/mm/memory_hotplug.c
@@ -617,115 +617,6 @@ int is_mem_section_removable(unsigned lo
}

/*
- * Confirm all pages in a range [start, end) is belongs to the same zone.
- */
-static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
-{
- unsigned long pfn;
- struct zone *zone = NULL;
- struct page *page;
- int i;
- for (pfn = start_pfn;
- pfn < end_pfn;
- pfn += MAX_ORDER_NR_PAGES) {
- i = 0;
- /* This is just a CONFIG_HOLES_IN_ZONE check.*/
- while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
- i++;
- if (i == MAX_ORDER_NR_PAGES)
- continue;
- page = pfn_to_page(pfn + i);
- if (zone && page_zone(page) != zone)
- return 0;
- zone = page_zone(page);
- }
- return 1;
-}
-
-/*
- * Scanning pfn is much easier than scanning lru list.
- * Scan pfn from start to end and Find LRU page.
- */
-int scan_lru_pages(unsigned long start, unsigned long end)
-{
- unsigned long pfn;
- struct page *page;
- for (pfn = start; pfn < end; pfn++) {
- if (pfn_valid(pfn)) {
- page = pfn_to_page(pfn);
- if (PageLRU(page))
- return pfn;
- }
- }
- return 0;
-}
-
-static struct page *
-hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
-{
- /* This should be improooooved!! */
- return alloc_page(GFP_HIGHUSER_MOVABLE);
-}
-
-#define NR_OFFLINE_AT_ONCE_PAGES (256)
-static int
-do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
-{
- unsigned long pfn;
- struct page *page;
- int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
- int not_managed = 0;
- int ret = 0;
- LIST_HEAD(source);
-
- for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
- if (!pfn_valid(pfn))
- continue;
- page = pfn_to_page(pfn);
- if (!page_count(page))
- continue;
- /*
- * We can skip free pages. And we can only deal with pages on
- * LRU.
- */
- ret = isolate_lru_page(page);
- if (!ret) { /* Success */
- list_add_tail(&page->lru, &source);
- move_pages--;
- inc_zone_page_state(page, NR_ISOLATED_ANON +
- page_is_file_cache(page));
-
- } else {
- /* Becasue we don't have big zone->lock. we should
- check this again here. */
- if (page_count(page))
- not_managed++;
-#ifdef CONFIG_DEBUG_VM
- printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
- pfn);
- dump_page(page);
-#endif
- }
- }
- ret = -EBUSY;
- if (not_managed) {
- if (!list_empty(&source))
- putback_lru_pages(&source);
- goto out;
- }
- ret = 0;
- if (list_empty(&source))
- goto out;
- /* this function returns # of failed pages */
- ret = migrate_pages(&source, hotremove_migrate_alloc, 0, 1);
- if (ret)
- putback_lru_pages(&source);
-
-out:
- return ret;
-}
-
-/*
* remove from free_area[] and mark all as Reserved.
*/
static int
Index: mmotm-1008/mm/page_isolation.c
===================================================================
--- mmotm-1008.orig/mm/page_isolation.c
+++ mmotm-1008/mm/page_isolation.c
@@ -1,10 +1,15 @@
/*
* linux/mm/page_isolation.c
+ * Contains a function for page migration based on page isolation by
+ * mirate-flag. Used in memory hotplug.
*/

#include <linux/mm.h>
#include <linux/page-isolation.h>
#include <linux/pageblock-flags.h>
+#include <linux/memcontrol.h>
+#include <linux/migrate.h>
+#include <linux/mm_inline.h>
#include "internal.h"

static inline struct page *
@@ -140,3 +145,112 @@ int test_pages_isolated(unsigned long st
spin_unlock_irqrestore(&zone->lock, flags);
return ret ? 0 : -EBUSY;
}
+
+/*
+ * Confirm all pages in a range [start, end) is belongs to the same zone.
+ */
+int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long pfn;
+ struct zone *zone = NULL;
+ struct page *page;
+ int i;
+ for (pfn = start_pfn;
+ pfn < end_pfn;
+ pfn += MAX_ORDER_NR_PAGES) {
+ i = 0;
+ /* This is just a CONFIG_HOLES_IN_ZONE check.*/
+ while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
+ i++;
+ if (i == MAX_ORDER_NR_PAGES)
+ continue;
+ page = pfn_to_page(pfn + i);
+ if (zone && page_zone(page) != zone)
+ return 0;
+ zone = page_zone(page);
+ }
+ return 1;
+}
+
+/*
+ * Scanning pfn is much easier than scanning lru list.
+ * Scan pfn from start to end and Find LRU page.
+ */
+int scan_lru_pages(unsigned long start, unsigned long end)
+{
+ unsigned long pfn;
+ struct page *page;
+ for (pfn = start; pfn < end; pfn++) {
+ if (pfn_valid(pfn)) {
+ page = pfn_to_page(pfn);
+ if (PageLRU(page))
+ return pfn;
+ }
+ }
+ return 0;
+}
+
+static struct page *
+hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
+{
+ /* This should be improooooved!! */
+ return alloc_page(GFP_HIGHUSER_MOVABLE);
+}
+
+#define NR_OFFLINE_AT_ONCE_PAGES (256)
+int do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long pfn;
+ struct page *page;
+ int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
+ int not_managed = 0;
+ int ret = 0;
+ LIST_HEAD(source);
+
+ for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
+ if (!pfn_valid(pfn))
+ continue;
+ page = pfn_to_page(pfn);
+ if (!page_count(page))
+ continue;
+ /*
+ * We can skip free pages. And we can only deal with pages on
+ * LRU.
+ */
+ ret = isolate_lru_page(page);
+ if (!ret) { /* Success */
+ list_add_tail(&page->lru, &source);
+ move_pages--;
+ inc_zone_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
+
+ } else {
+ /* Becasue we don't have big zone->lock. we should
+ check this again here. */
+ if (page_count(page))
+ not_managed++;
+#ifdef CONFIG_DEBUG_VM
+ printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+ pfn);
+ dump_page(page);
+#endif
+ }
+ }
+ ret = -EBUSY;
+ if (not_managed) {
+ if (!list_empty(&source))
+ putback_lru_pages(&source);
+ goto out;
+ }
+ ret = 0;
+ if (list_empty(&source))
+ goto out;
+ /* this function returns # of failed pages */
+ ret = migrate_pages(&source, hotremove_migrate_alloc, 0, 1);
+ if (ret)
+ putback_lru_pages(&source);
+
+out:
+ return ret;
+}
+





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