Commit a4bafffb authored by Mel Gorman's avatar Mel Gorman Committed by Andrew Morton
Browse files

mm/page_alloc: simplify locking during free_unref_page_list 

While freeing a large list, the zone lock will be released and reacquired
to avoid long hold times since commit c24ad77d ("mm/page_alloc.c:
avoid excessive IRQ disabled times in free_unref_page_list()").  As
suggested by Vlastimil Babka, the lockrelease/reacquire logic can be
simplified by reusing the logic that acquires a different lock when
changing zones.

Link: https://lkml.kernel.org/r/20221122131229.5263-3-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 57490774

mm/page_alloc.c

+9 −16
Original line number Diff line number Diff line
@@ -3525,13 +3525,19 @@ void free_unref_page_list(struct list_head *list) 
		list_del(&page->lru);

		migratetype = get_pcppage_migratetype(page);



		/* Different zone, different pcp lock. */

		if (zone != locked_zone) {

		/*

		 * Either different zone requiring a different pcp lock or

		 * excessive lock hold times when freeing a large list of

		 * pages.

		 */

		if (zone != locked_zone || batch_count == SWAP_CLUSTER_MAX) {

			if (pcp) {

				pcp_spin_unlock(pcp);

				pcp_trylock_finish(UP_flags);

			}



			batch_count = 0;



			/*

			 * trylock is necessary as pages may be getting freed

			 * from IRQ or SoftIRQ context after an IO completion.
@@ -3546,7 +3552,6 @@ void free_unref_page_list(struct list_head *list) 
				continue;

			}

			locked_zone = zone;

			batch_count = 0;

		}



		/*
@@ -3558,19 +3563,7 @@ void free_unref_page_list(struct list_head *list) 


		trace_mm_page_free_batched(page);

		free_unref_page_commit(zone, pcp, page, migratetype, 0);



		/*

		 * Guard against excessive lock hold times when freeing

		 * a large list of pages. Lock will be reacquired if

		 * necessary on the next iteration.

		 */

		if (++batch_count == SWAP_CLUSTER_MAX) {

			pcp_spin_unlock(pcp);

			pcp_trylock_finish(UP_flags);

			batch_count = 0;

			pcp = NULL;

			locked_zone = NULL;

		}

		batch_count++;

	}



	if (pcp) {