From 96a5c186efff9906c58fa24ab05d0cc3ee000a00 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Tue, 26 Mar 2024 14:11:32 +0800 Subject: mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone On one node, for lower zone's ->lowmem_reserve[], it will show how much memory is reserved in this lower zone to avoid excessive page allocation from the relevant higher zone's fallback allocation. However, currently lower zone's lowmem_reserve[] element will be filled even though the relevant higher zone is empty. That doesnt' make sense and can cause confusion. E.g on node 0 of one system as below, it has zone DMA/DMA32/NORMAL/MOVABLE/DEVICE, among them zone MOVABLE/DEVICE are the highest and both are empty. In zone DMA/DMA32's protection array, we can see that it has value for zone MOVABLE and DEVICE. Node 0, zone DMA ...... pages free 2816 boost 0 min 7 low 10 high 13 spanned 4095 present 3998 managed 3840 cma 0 protection: (0, 1582, 23716, 23716, 23716) ...... Node 0, zone DMA32 pages free 403269 boost 0 min 753 low 1158 high 1563 spanned 1044480 present 487039 managed 405070 cma 0 protection: (0, 0, 22134, 22134, 22134) ...... Node 0, zone Normal pages free 5423879 boost 0 min 10539 low 16205 high 21871 spanned 5767168 present 5767168 managed 5666438 cma 0 protection: (0, 0, 0, 0, 0) ...... Node 0, zone Movable pages free 0 boost 0 min 32 low 32 high 32 spanned 0 present 0 managed 0 cma 0 protection: (0, 0, 0, 0, 0) Node 0, zone Device pages free 0 boost 0 min 0 low 0 high 0 spanned 0 present 0 managed 0 cma 0 protection: (0, 0, 0, 0, 0) Here, clear out the element value in lower zone's ->lowmem_reserve[] if the relevant higher zone is empty. And also replace space with tab in _deferred_grow_zone() Link: https://lkml.kernel.org/r/20240326061134.1055295-7-bhe@redhat.com Signed-off-by: Baoquan He Cc: Mel Gorman Cc: "Mike Rapoport (IBM)" Signed-off-by: Andrew Morton --- mm/page_alloc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d932f406c0c1..875cec8c7708 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -315,7 +315,7 @@ static inline bool deferred_pages_enabled(void) static bool __ref _deferred_grow_zone(struct zone *zone, unsigned int order) { - return deferred_grow_zone(zone, order); + return deferred_grow_zone(zone, order); } #else static inline bool deferred_pages_enabled(void) @@ -5903,10 +5903,11 @@ static void setup_per_zone_lowmem_reserve(void) for (j = i + 1; j < MAX_NR_ZONES; j++) { struct zone *upper_zone = &pgdat->node_zones[j]; + bool empty = !zone_managed_pages(upper_zone); managed_pages += zone_managed_pages(upper_zone); - if (clear) + if (clear || empty) zone->lowmem_reserve[j] = 0; else zone->lowmem_reserve[j] = managed_pages / ratio; -- cgit v1.2.3