mm/compaction.c: periodically schedule when freeing pages
We've been getting warnings about an excessive amount of time spent
allocating pages for migration during memory compaction without
scheduling. isolate_freepages_block() already periodically checks for
contended locks or the need to schedule, but isolate_freepages() never
does.
When a zone is massively long and no suitable targets can be found, this
iteration can be quite expensive without ever doing cond_resched().
Check periodically for the need to reschedule while the compaction free
scanner iterates.
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/compaction.c b/mm/compaction.c
index c437893..b5326b1 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -677,6 +677,13 @@
pfn -= pageblock_nr_pages) {
unsigned long isolated;
+ /*
+ * This can iterate a massively long zone without finding any
+ * suitable migration targets, so periodically check if we need
+ * to schedule.
+ */
+ cond_resched();
+
if (!pfn_valid(pfn))
continue;