From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
iamjoonsoo.kim@lge.com, mhocko@kernel.org, bhe@redhat.com,
mgorman@techsingularity.net, rientjes@google.com
Subject: [PATCH v2 2/3] mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty
Date: Thu, 2 Apr 2020 22:01:12 +0800 [thread overview]
Message-ID: <20200402140113.3696-3-bhe@redhat.com> (raw)
In-Reply-To: <20200402140113.3696-1-bhe@redhat.com>
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@redhat.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
next prev parent reply other threads:[~2020-04-02 14:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 14:01 [PATCH v2 0/3] improvements about lowmem_reserve and /proc/zoneinfo Baoquan He
2020-04-02 14:01 ` [PATCH v2 1/3] mm/page_alloc.c: only tune sysctl_lowmem_reserve_ratio value once when changing it Baoquan He
2020-04-02 14:01 ` Baoquan He [this message]
2020-04-02 14:01 ` [PATCH v2 3/3] mm/vmstat.c: do not show lowmem reserve protection information of empty zone Baoquan He
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