[PATCH v2 1/7] mm/compaction: split freepages without holding the zone lock

js1304
2016-05-26T02:38:00Z

From: Joonsoo Kim <iamjoonsoo.kim@lge.com>

We don't need to split freepages with holding the zone lock. It will cause
more contention on zone lock so not desirable.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
include/linux/mm.h | 1 -
mm/compaction.c | 42 ++++++++++++++++++++++++++++++------------
mm/page_alloc.c | 27 ---------------------------
3 files changed, 30 insertions(+), 40 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a00ec81..1a1782c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -537,7 +537,6 @@ void __put_page(struct page *page);
void put_pages_list(struct list_head *pages);

void split_page(struct page *page, unsigned int order);
-int split_free_page(struct page *page);

/*
* Compound pages have a destructor function. Provide a
diff --git a/mm/compaction.c b/mm/compaction.c
index 1427366..8e013eb 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -65,13 +65,31 @@ static unsigned long release_freepages(struct list_head *freelist)

static void map_pages(struct list_head *list)
{
- struct page *page;
+ unsigned int i, order, nr_pages;
+ struct page *page, *next;
+ LIST_HEAD(tmp_list);
+
+ list_for_each_entry_safe(page, next, list, lru) {
+ list_del(&page->lru);
+
+ order = page_private(page);
+ nr_pages = 1 << order;
+ set_page_private(page, 0);
+ set_page_refcounted(page);
+
+ arch_alloc_page(page, order);
+ kernel_map_pages(page, nr_pages, 1);
+ kasan_alloc_pages(page, order);
+ if (order)
+ split_page(page, order);

- list_for_each_entry(page, list, lru) {
- arch_alloc_page(page, 0);
- kernel_map_pages(page, 1, 1);
- kasan_alloc_pages(page, 0);
+ for (i = 0; i < nr_pages; i++) {
+ list_add(&page->lru, &tmp_list);
+ page++;
+ }
}
+
+ list_splice(&tmp_list, list);
}

static inline bool migrate_async_suitable(int migratetype)
@@ -368,12 +386,13 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
unsigned long flags = 0;
bool locked = false;
unsigned long blockpfn = *start_pfn;
+ unsigned int order;

cursor = pfn_to_page(blockpfn);

/* Isolate free pages. */
for (; blockpfn < end_pfn; blockpfn++, cursor++) {
- int isolated, i;
+ int isolated;
struct page *page = cursor;

/*
@@ -439,13 +458,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
goto isolate_fail;
}

- /* Found a free page, break it into order-0 pages */
- isolated = split_free_page(page);
+ /* Found a free page, will break it into order-0 pages */
+ order = page_order(page);
+ isolated = __isolate_free_page(page, page_order(page));
+ set_page_private(page, order);
total_isolated += isolated;
- for (i = 0; i < isolated; i++) {
- list_add(&page->lru, freelist);
- page++;
- }
+ list_add_tail(&page->lru, freelist);

/* If a page was split, advance to the end of it */
if (isolated) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d27e8b9..5134f46 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2525,33 +2525,6 @@ int __isolate_free_page(struct page *page, unsigned int order)
}

/*
- * Similar to split_page except the page is already free. As this is only
- * being used for migration, the migratetype of the block also changes.
- * As this is called with interrupts disabled, the caller is responsible
- * for calling arch_alloc_page() and kernel_map_page() after interrupts
- * are enabled.
- *
- * Note: this is probably too low level an operation for use in drivers.
- * Please consult with lkml before using this in your driver.
- */
-int split_free_page(struct page *page)
-{
- unsigned int order;
- int nr_pages;
-
- order = page_order(page);
-
- nr_pages = __isolate_free_page(page, order);
- if (!nr_pages)
- return 0;
-
- /* Split into individual pages */
- set_page_refcounted(page);
- split_page(page, order);
- return nr_pages;
-}
-
-/*
* Update NUMA hit/miss statistics
*
* Must be called with interrupts disabled.
--
1.9.1