free_pcppages_bulk() selects pages to free by round-robining between
lists. Originally this was to evenly shrink pages by migratetype
but uneven freeing is inevitable due to high pages. Simplify list
selection by starting with a list that definitely has pages on it in
free_unref_page_commit() and for drain, it does not matter where draining
starts as all pages are removed.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 34 +++++++++++-----------------------
1 file changed, 11 insertions(+), 23 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c5110fdeb115..5e8c7cbe7a41 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1447,13 +1447,11 @@ static inline void prefetch_buddy(struct page *page, unsigned int order)
* count is the number of pages to free.
*/
static void free_pcppages_bulk(struct zone *zone, int count,
- struct per_cpu_pages *pcp)
+ struct per_cpu_pages *pcp,
+ int pindex)
{
- int pindex = 0;
int min_pindex = 0;
int max_pindex = NR_PCP_LISTS - 1;
- int batch_free = 0;
- int nr_freed = 0;
unsigned int order;
int prefetch_nr = READ_ONCE(pcp->batch);
bool isolated_pageblocks;
@@ -1467,16 +1465,10 @@ static void free_pcppages_bulk(struct zone *zone, int count,
count = min(pcp->count, count);
while (count > 0) {
struct list_head *list;
+ int nr_pages;
- /*
- * Remove pages from lists in a round-robin fashion. A
- * batch_free count is maintained that is incremented when an
- * empty list is encountered. This is so more pages are freed
- * off fuller lists instead of spinning excessively around empty
- * lists
- */
+ /* Remove pages from lists in a round-robin fashion. */
do {
- batch_free++;
if (++pindex == NR_PCP_LISTS)
pindex = 0;
list = &pcp->lists[pindex];
@@ -1489,18 +1481,15 @@ static void free_pcppages_bulk(struct zone *zone, int count,
min_pindex++;
} while (1);
- /* This is the only non-empty list. Free them all. */
- if (batch_free >= max_pindex - min_pindex)
- batch_free = count;
-
order = pindex_to_order(pindex);
+ nr_pages = 1 << order;
BUILD_BUG_ON(MAX_ORDER >= (1<<NR_PCP_ORDER_WIDTH));
do {
page = list_last_entry(list, struct page, lru);
/* must delete to avoid corrupting pcp list */
list_del(&page->lru);
- nr_freed += 1 << order;
- count -= 1 << order;
+ count -= nr_pages;
+ pcp->count -= nr_pages;
if (bulkfree_pcp_prepare(page))
continue;
@@ -1524,9 +1513,8 @@ static void free_pcppages_bulk(struct zone *zone, int count,
prefetch_buddy(page, order);
prefetch_nr--;
}
- } while (count > 0 && --batch_free && !list_empty(list));
+ } while (count > 0 && !list_empty(list));
}
- pcp->count -= nr_freed;
/*
* local_lock_irq held so equivalent to spin_lock_irqsave for
@@ -3095,7 +3083,7 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
batch = READ_ONCE(pcp->batch);
to_drain = min(pcp->count, batch);
if (to_drain > 0)
- free_pcppages_bulk(zone, to_drain, pcp);
+ free_pcppages_bulk(zone, to_drain, pcp, 0);
local_unlock_irqrestore(&pagesets.lock, flags);
}
#endif
@@ -3116,7 +3104,7 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone)
pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
if (pcp->count)
- free_pcppages_bulk(zone, pcp->count, pcp);
+ free_pcppages_bulk(zone, pcp->count, pcp, 0);
local_unlock_irqrestore(&pagesets.lock, flags);
}
@@ -3397,7 +3385,7 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn,
if (pcp->count >= high) {
int batch = READ_ONCE(pcp->batch);
- free_pcppages_bulk(zone, nr_pcp_free(pcp, high, batch), pcp);
+ free_pcppages_bulk(zone, nr_pcp_free(pcp, high, batch), pcp, pindex);
}
}
--
2.31.1
