[099/227] mm/page_alloc: track range of active PCP lists during bulk free

Commit Message

Andrew Morton March 22, 2022, 9:43 p.m. UTC

From: Mel Gorman <[e-mail]>
Subject: mm/page_alloc: track range of active PCP lists during bulk free

free_pcppages_bulk() frees pages in a round-robin fashion.  Originally,
this was dealing only with migratetypes but storing high-order pages means
that there can be many more empty lists that are uselessly checked.  Track
the minimum and maximum active pindex to reduce the search space.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mel Gorman <[e-mail]>
Reviewed-by: Vlastimil Babka <[e-mail]>
Tested-by: Aaron Lu <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-page_alloc-track-range-of-active-pcp-lists-during-bulk-free
+++ a/mm/page_alloc.c
@@ -1447,6 +1447,8 @@  static void free_pcppages_bulk(struct zo
 					struct per_cpu_pages *pcp)
 {
 	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;
@@ -1472,13 +1474,20 @@  static void free_pcppages_bulk(struct zo
 		 */
 		do {
 			batch_free++;
-			if (++pindex == NR_PCP_LISTS)
-				pindex = 0;
+			if (++pindex > max_pindex)
+				pindex = min_pindex;
 			list = &pcp->lists[pindex];
-		} while (list_empty(list));
+			if (!list_empty(list))
+				break;
+
+			if (pindex == max_pindex)
+				max_pindex--;
+			if (pindex == min_pindex)
+				min_pindex++;
+		} while (1);
 
 		/* This is the only non-empty list. Free them all. */
-		if (batch_free == NR_PCP_LISTS)
+		if (batch_free >= max_pindex - min_pindex)
 			batch_free = count;
 
 		order = pindex_to_order(pindex);