6.11: base: Get rid of "ZEN: mm: Don't hog the CPU and zone lock in r…

…mqueue_bulk()" patch

linux-tkg-patches/6.11/0003-glitched-base.patch

@@ -648,83 +648,6 @@ index 5f1ae07d724b88..97cda629c9e909 100644
  #endif /* CONFIG_HUGETLB_PAGE */
 
 
-From f22bc56be85e69c71c8e36041193856bb8b01525 Mon Sep 17 00:00:00 2001
-From: Sultan Alsawaf <[email protected]>
-Date: Wed, 20 Oct 2021 20:50:32 -0700
-Subject: [PATCH] ZEN: mm: Don't hog the CPU and zone lock in rmqueue_bulk()
-
-There is noticeable scheduling latency and heavy zone lock contention
-stemming from rmqueue_bulk's single hold of the zone lock while doing
-its work, as seen with the preemptoff tracer. There's no actual need for
-rmqueue_bulk() to hold the zone lock the entire time; it only does so
-for supposed efficiency. As such, we can relax the zone lock and even
-reschedule when IRQs are enabled in order to keep the scheduling delays
-and zone lock contention at bay. Forward progress is still guaranteed,
-as the zone lock can only be relaxed after page removal.
-
-With this change, rmqueue_bulk() no longer appears as a serious offender
-in the preemptoff tracer, and system latency is noticeably improved.
-
-Signed-off-by: Sultan Alsawaf <[email protected]>
----
- mm/page_alloc.c | 23 ++++++++++++++++++-----
- 1 file changed, 18 insertions(+), 5 deletions(-)
-
-diff --git a/mm/page_alloc.c b/mm/page_alloc.c
-index a0b0397e29ee4c..87a983a356530c 100644
---- a/mm/page_alloc.c
-+++ b/mm/page_alloc.c
-@@ -3118,15 +3119,16 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype,
- }
-
- /*
-- * Obtain a specified number of elements from the buddy allocator, all under
-- * a single hold of the lock, for efficiency.  Add them to the supplied list.
-- * Returns the number of new pages which were placed at *list.
-+ * Obtain a specified number of elements from the buddy allocator, and relax the
-+ * zone lock when needed. Add them to the supplied list. Returns the number of
-+ * new pages which were placed at *list.
-  */
- static int rmqueue_bulk(struct zone *zone, unsigned int order,
- 			unsigned long count, struct list_head *list,
- 			int migratetype, unsigned int alloc_flags)
- {
-	unsigned long flags;
--	int i;
-+	const bool can_resched = !preempt_count() && !irqs_disabled();
-+	int i, allocated = 0, last_mod = 0;
-
- 	/* Caller must hold IRQ-safe pcp->lock so IRQs are disabled. */
- 	spin_lock(&zone->lock);
-@@ -3137,6 +3138,18 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
- 		if (unlikely(page == NULL))
- 			break;
-
-+		/* Reschedule and ease the contention on the lock if needed */
-+		if (i + 1 < count && ((can_resched && need_resched()) ||
-+				      spin_needbreak(&zone->lock))) {
-+			__mod_zone_page_state(zone, NR_FREE_PAGES,
-+					      -((i + 1 - last_mod) << order));
-+			last_mod = i + 1;
-+			spin_unlock(&zone->lock);
-+			if (can_resched)
-+				cond_resched();
-+			spin_lock(&zone->lock);
-+		}
-+
- 		if (unlikely(check_pcp_refill(page, order)))
- 			continue;
-
-@@ -3163,7 +3176,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
- 	 * on i. Do not confuse with 'allocated' which is the number of
- 	 * pages added to the pcp list.
- 	 */
--	__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
-+	__mod_zone_page_state(zone, NR_FREE_PAGES, -((i - last_mod) << order));
- 	spin_unlock(&zone->lock);
- 	return allocated;
- }
-
 From 6329525a0fa10cd13f39b76948b1296150f75c95 Mon Sep 17 00:00:00 2001
 From: Alexandre Frade <[email protected]>
 Date: Mon, 29 Aug 2022 16:47:26 +0000