[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20200324142229.12028-3-bhe@redhat.com>
Date: Tue, 24 Mar 2020 22:22:26 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org,
iamjoonsoo.kim@....com, hannes@...xchg.org, mhocko@...nel.org,
vbabka@...e.cz, bhe@...hat.com
Subject: [PATCH 2/5] mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty
When requesting memory allocation from a specific zone is not satisfied,
it will fall to lower zone to try allocating memory. In this case,
lower zone's ->lowmem_reserve[] will help protect its own memory resource.
The higher the relevant ->lowmem_reserve[] is, the harder the upper zone
can get memory from this lower zone.
However, this protection mechanism should be applied to populated zone,
but not an empty zone. So filling ->lowmem_reserve[] for empty zone is
not necessary, and may mislead people that it's valid data in that zone.
Node 2, zone DMA
pages free 0
min 0
low 0
high 0
spanned 0
present 0
managed 0
protection: (0, 0, 1024, 1024)
Node 2, zone DMA32
pages free 0
min 0
low 0
high 0
spanned 0
present 0
managed 0
protection: (0, 0, 1024, 1024)
Node 2, zone Normal
per-node stats
nr_inactive_anon 0
nr_active_anon 143
nr_inactive_file 0
nr_active_file 0
nr_unevictable 0
nr_slab_reclaimable 45
nr_slab_unreclaimable 254
Here clear out zone->lowmem_reserve[] if zone is empty.
Signed-off-by: Baoquan He <bhe@...hat.com>
---
mm/page_alloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c0c788798d8b..138a56c0f48f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7840,8 +7840,10 @@ static void setup_per_zone_lowmem_reserve(void)
idx--;
lower_zone = pgdat->node_zones + idx;
- if (!sysctl_lowmem_reserve_ratio[idx]) {
+ if (!sysctl_lowmem_reserve_ratio[idx] ||
+ !zone_managed_pages(lower_zone)) {
lower_zone->lowmem_reserve[j] = 0;
+ continue;
} else {
lower_zone->lowmem_reserve[j] =
managed_pages / sysctl_lowmem_reserve_ratio[idx];
--
2.17.2
Powered by blists - more mailing lists