[PATCH 02/22] mm: page allocator: Push down where IRQs are disabled during page free

Mel Gorman
2013-05-08T16:03:14Z

This patch pushes IRQ disabling down into free_one_page(). This simplifies
the logic in free_hot_cold_page() slightly by making it clear that zone->lock
is an IRQ-safe spinlock. The current arrangement has the IRQ disabling
happen in one function and the spinlock been taken in another. Functionally,
there is no difference.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/page_alloc.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 277ecee..50c9315 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -686,14 +686,18 @@ static void free_pcppages_bulk(struct zone *zone, int count,
static void free_one_page(struct zone *zone, struct page *page, int order,
int migratetype)
{
- spin_lock(&zone->lock);
+ unsigned long flags;
+ set_freepage_migratetype(page, migratetype);
+
+ spin_lock_irqsave(&zone->lock, flags);
zone->all_unreclaimable = 0;
zone->pages_scanned = 0;
+ __count_vm_events(PGFREE, 1 << order);

__free_one_page(page, zone, order, migratetype);
if (unlikely(!is_migrate_isolate(migratetype)))
__mod_zone_freepage_state(zone, 1 << order, migratetype);
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
}

static bool free_pages_prepare(struct page *page, unsigned int order)
@@ -724,7 +728,6 @@ static bool free_pages_prepare(struct page *page, unsigned int order)

static void __free_pages_ok(struct page *page, unsigned int order)
{
- unsigned long flags;
int migratetype;

if (!free_pages_prepare(page, order))
@@ -732,11 +735,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)

migratetype = get_pageblock_migratetype(page);

- local_irq_save(flags);
- __count_vm_events(PGFREE, 1 << order);
- set_freepage_migratetype(page, migratetype);
free_one_page(page_zone(page), page, order, migratetype);
- local_irq_restore(flags);
}

/*
@@ -1325,8 +1324,6 @@ void free_hot_cold_page(struct page *page, int cold)

migratetype = get_pageblock_migratetype(page);
set_freepage_migratetype(page, migratetype);
- local_irq_save(flags);
- __count_vm_event(PGFREE);

/*
* We only track unmovable, reclaimable and movable on pcp lists.
@@ -1338,11 +1335,14 @@ void free_hot_cold_page(struct page *page, int cold)
if (migratetype >= MIGRATE_PCPTYPES) {
if (unlikely(is_migrate_isolate(migratetype))) {
free_one_page(zone, page, 0, migratetype);
- goto out;
+ return;
}
migratetype = MIGRATE_MOVABLE;
}

+ local_irq_save(flags);
+ __count_vm_event(PGFREE);
+
pcp = &this_cpu_ptr(zone->pageset)->pcp;
if (cold)
list_add_tail(&page->lru, &pcp->lists[migratetype]);
@@ -1354,7 +1354,6 @@ void free_hot_cold_page(struct page *page, int cold)
pcp->count -= pcp->batch;
}

-out:
local_irq_restore(flags);
}

--
1.8.1.4