On 12/01/2016 01:24 AM, Mel Gorman wrote:
...
@@ -1096,28 +1097,29 @@ static void free_pcppages_bulk(struct zone *zone, int count,
if (nr_scanned)
__mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
- while (count) {
+ while (count > 0) {
struct page *page;
struct list_head *list;
+ unsigned int order;
/*
* 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
+ * empty list is encountered. This is not exact due to
+ * high-order but percision is not required.
*/
do {
batch_free++;
- if (++migratetype == MIGRATE_PCPTYPES)
- migratetype = 0;
- list = &pcp->lists[migratetype];
+ if (++pindex == NR_PCP_LISTS)
+ pindex = 0;
+ list = &pcp->lists[pindex];
} while (list_empty(list));
/* This is the only non-empty list. Free them all. */
- if (batch_free == MIGRATE_PCPTYPES)
+ if (batch_free == NR_PCP_LISTS)
batch_free = count;
+ order = pindex_to_order(pindex);
do {
int mt; /* migratetype of the to-be-freed page */
@@ -1135,11 +1137,14 @@ static void free_pcppages_bulk(struct zone *zone, int count,
if (bulkfree_pcp_prepare(page))
continue;
Hmm I think that if this hits, we don't decrease count/increase nr_freed and
pcp->count will become wrong. And if we are unlucky/doing full drain, all lists
will get empty, but as count stays e.g. 1, we loop forever on the outer while()?
BTW, I think there's a similar problem (but not introduced by this patch) in
rmqueue_bulk() and its
if (unlikely(check_pcp_refill(page)))
continue;
This might result in pcp->count being higher than actual pages. That one would
be introduced by 479f854a207c ("mm, page_alloc: defer debugging checks of pages
allocated from the PCP").
- __free_one_page(page, page_to_pfn(page), zone, 0, mt);
- trace_mm_page_pcpu_drain(page, 0, mt);
- } while (--count && --batch_free && !list_empty(list));
+ __free_one_page(page, page_to_pfn(page), zone, order, mt);
+ trace_mm_page_pcpu_drain(page, order, mt);
+ nr_freed += (1 << order);
+ count -= (1 << order);
+ } while (count > 0 && --batch_free && !list_empty(list));
}
spin_unlock(&zone->lock);
+ pcp->count -= nr_freed;
}
static void free_one_page(struct zone *zone,
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>