linux-kernel - [PATCH v4] mm/page_alloc: fix min_free_kbytes calculation regarding ZONE

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Message-ID: <37d8c6c3-0dd1-94b1-19cd-4743968b0fce@chinatelecom.cn>
Date:   Wed, 21 Jun 2023 21:48:01 +0800
From:   liuq <liuq131@...natelecom.cn>
To:     akpm@...ux-foundation.org, liuq131@...natelecom.cn
Cc:     "Huang, Ying" <ying.huang@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4] mm/page_alloc: fix min_free_kbytes calculation regarding
 ZONE_MOVABLE

The current calculation of min_free_kbytes only uses ZONE_DMA and
ZONE_NORMAL pages,but the ZONE_MOVABLE zone->_watermark[WMARK_MIN]
will also divide part of min_free_kbytes.This will cause the min
watermark of ZONE_NORMAL to be too small in the presence of ZONE_MOVEABLE.

__GFP_HIGH and PF_MEMALLOC allocations usually don't need movable
zone pages, so just like ZONE_HIGHMEM, cap pages_min to a small
value in __setup_per_zone_wmarks.

On my testing machine with 16GB of memory (transparent hugepage is
turned off by default, and movablecore=12G is configured)
The following is a comparative test data of watermark_min

		no patch	add patch
ZONE_DMA	1		8
ZONE_DMA32	151		709
ZONE_NORMAL	233		1113
ZONE_MOVABLE	1434		128
min_free_kbytes	7288		7326

Signed-off-by: liuq<liuq131@...natelecom.cn>
---
  mm/page_alloc.c | 12 ++++++------
  1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 47421bedc12b..590ed8725e09 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6362,9 +6362,9 @@ static void __setup_per_zone_wmarks(void)
  	struct zone *zone;
  	unsigned long flags;
  
-	/* Calculate total number of !ZONE_HIGHMEM pages */
+	/* Calculate total number of !ZONE_HIGHMEM and !ZONE_MOVABLE pages */
  	for_each_zone(zone) {
-		if (!is_highmem(zone))
+		if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
  			lowmem_pages += zone_managed_pages(zone);
  	}
  
@@ -6374,15 +6374,15 @@ static void __setup_per_zone_wmarks(void)
  		spin_lock_irqsave(&zone->lock, flags);
  		tmp = (u64)pages_min * zone_managed_pages(zone);
  		do_div(tmp, lowmem_pages);
-		if (is_highmem(zone)) {
+		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
  			/*
  			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
-			 * need highmem pages, so cap pages_min to a small
-			 * value here.
+			 * need highmem and movable zones pages, so cap pages_min
+			 * to a small value here.
  			 *
  			 * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
  			 * deltas control async page reclaim, and so should
-			 * not be capped for highmem.
+			 * not be capped for highmem and movable zones.
  			 */
  			unsigned long min_pages;
  
-- 2.27.0