[107/227] mm/page_alloc: call check_new_pages() while zone spinlock is not held

Commit Message

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

From: Eric Dumazet <[e-mail]>
Subject: mm/page_alloc: call check_new_pages() while zone spinlock is not held

For high order pages not using pcp, rmqueue() is currently calling the
costly check_new_pages() while zone spinlock is held, and hard irqs
masked.

This is not needed, we can release the spinlock sooner to reduce zone
spinlock contention.

Note that after this patch, we call __mod_zone_freepage_state() before
deciding to leak the page because it is in bad state.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Eric Dumazet <[e-mail]>
Reviewed-by: Shakeel Butt <[e-mail]>
Acked-by: David Rientjes <[e-mail]>
Acked-by: Mel Gorman <[e-mail]>
Reviewed-by: Vlastimil Babka <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Wei Xu <[e-mail]>
Cc: Greg Thelen <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-page_alloc-call-check_new_pages-while-zone-spinlock-is-not-held
+++ a/mm/page_alloc.c
@@ -3665,10 +3665,10 @@  struct page *rmqueue(struct zone *prefer
 	 * allocate greater than order-1 page units with __GFP_NOFAIL.
 	 */
 	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
-	spin_lock_irqsave(&zone->lock, flags);
 
 	do {
 		page = NULL;
+		spin_lock_irqsave(&zone->lock, flags);
 		/*
 		 * order-0 request can reach here when the pcplist is skipped
 		 * due to non-CMA allocation context. HIGHATOMIC area is
@@ -3680,15 +3680,15 @@  struct page *rmqueue(struct zone *prefer
 			if (page)
 				trace_mm_page_alloc_zone_locked(page, order, migratetype);
 		}
-		if (!page)
+		if (!page) {
 			page = __rmqueue(zone, order, migratetype, alloc_flags);
-	} while (page && check_new_pages(page, order));
-	if (!page)
-		goto failed;
-
-	__mod_zone_freepage_state(zone, -(1 << order),
-				  get_pcppage_migratetype(page));
-	spin_unlock_irqrestore(&zone->lock, flags);
+			if (!page)
+				goto failed;
+		}
+		__mod_zone_freepage_state(zone, -(1 << order),
+					  get_pcppage_migratetype(page));
+		spin_unlock_irqrestore(&zone->lock, flags);
+	} while (check_new_pages(page, order));
 
 	__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
 	zone_statistics(preferred_zone, zone, 1);