If we use a division operation, we can compute a batch count more closed
to ideal value. With this value, we can remove at least one list in each
iteration. So we end the logic within MIGRATE_PCPTYPES iteration.
This makes logic more simple and understandable. In addition,
batching to free more pages may be helpful to cache usage.
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b212554..2632131 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -633,53 +633,71 @@ static inline int free_pages_check(struct page *page)
static void free_pcppages_bulk(struct zone *zone, int count,
struct per_cpu_pages *pcp)
{
- int migratetype = 0;
- int batch_free = 0;
+ struct page *page;
+ struct list_head *list;
int to_free = count;
+ int batch_free;
+ int mt, page_mt;
+ int nr_list;
+ int i;
+ bool all = false;
+
+ if (pcp->count == to_free)
+ all = true;
spin_lock(&zone->lock);
zone->all_unreclaimable = 0;
zone->pages_scanned = 0;
- while (to_free) {
- struct page *page;
- struct list_head *list;
+redo:
+ /* Count non-empty list */
+ nr_list = 0;
+ for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
+ list = &pcp->lists[mt];
+ if (!list_empty(list))
+ nr_list++;
+ }
- /*
- * 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
- */
- do {
- batch_free++;
- if (++migratetype == MIGRATE_PCPTYPES)
- migratetype = 0;
- list = &pcp->lists[migratetype];
- } while (list_empty(list));
+ /*
+ * If there is only one non-empty list, free them all.
+ * Otherwise, remove pages from lists in a round-robin fashion.
+ * batch_free is set to remove at least one list.
+ */
+ if (all || nr_list == 1)
+ batch_free = to_free;
+ else
+ batch_free = to_free / nr_list;
- /* This is the only non-empty list. Free them all. */
- if (batch_free == MIGRATE_PCPTYPES)
- batch_free = to_free;
+ for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
+ list = &pcp->lists[mt];
- do {
- int mt; /* migratetype of the to-be-freed page */
+ for (i = 0; i < batch_free; i++) {
+ if (list_empty(list))
+ break;
+ to_free--;
page = list_entry(list->prev, struct page, lru);
+
/* must delete as __free_one_page list manipulates */
list_del(&page->lru);
- mt = get_freepage_migratetype(page);
+ page_mt = get_freepage_migratetype(page);
/* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
- __free_one_page(page, zone, 0, mt);
- trace_mm_page_pcpu_drain(page, 0, mt);
- if (likely(!is_migrate_isolate_page(page))) {
- __mod_zone_page_state(zone, NR_FREE_PAGES, 1);
- if (is_migrate_cma(mt))
- __mod_zone_page_state(zone,
NR_FREE_CMA_PAGES, 1);
- }
- } while (--to_free && --batch_free && !list_empty(list));
+ __free_one_page(page, zone, 0, page_mt);
+ trace_mm_page_pcpu_drain(page, 0, page_mt);
+
+ if (unlikely(is_migrate_isolate_page(page)))
+ continue;
+
+ __mod_zone_page_state(zone, NR_FREE_PAGES, 1);
+ if (is_migrate_cma(page_mt))
+ __mod_zone_page_state(zone,
+ NR_FREE_CMA_PAGES, 1);
+ }
}
+
+ if (to_free)
+ goto redo;
+
spin_unlock(&zone->lock);
}
--
1.7.9.5
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