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Message-Id: <20170524122411.25212-2-mhocko@kernel.org>
Date: Wed, 24 May 2017 14:24:10 +0200
From: Michal Hocko <mhocko@...nel.org>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
Andrea Arcangeli <aarcange@...hat.com>,
Jerome Glisse <jglisse@...hat.com>,
Reza Arbab <arbab@...ux.vnet.ibm.com>,
Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
Andi Kleen <ak@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Daniel Kiper <daniel.kiper@...cle.com>,
Igor Mammedov <imammedo@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
Michal Hocko <mhocko@...e.com>
Subject: [RFC PATCH 1/2] mm, memory_hotplug: drop artificial restriction on online/offline
From: Michal Hocko <mhocko@...e.com>
74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
memory") has added can_offline_normal which checks the amount of
memory in !movable zones as long as CONFIG_MOVABLE_NODE is disable.
It disallows to offline memory if there is nothing left with a
justification that "memory-management acts bad when we have nodes which
is online but don't have any normal memory".
74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
memory") has introduced a restriction that every numa node has to have
at least some memory in !movable zones before a first movable memory
can be onlined if !CONFIG_MOVABLE_NODE with the same justification
While it is true that not having _any_ memory for kernel allocations on
a NUMA node is far from great and such a node would be quite subotimal
because all kernel allocations will have to fallback to another NUMA
node but there is no reason to disallow such a configuration in
principle.
Besides that there is not really a big difference to have one memblock
for ZONE_NORMAL available or none. With 128MB size memblocks the system
might trash on the kernel allocations requests anyway. It is really
hard to draw a line on how much normal memory is really sufficient so
we have to rely on administrator to configure system sanely therefore
drop the artificial restriction and remove can_offline_normal and
can_online_high_movable altogether.
Signed-off-by: Michal Hocko <mhocko@...e.com>
mm, memory_hotplug: drop can_online_high_movable
because "memory-management acts
bad when we have nodes which is online but don't have any normal memory.
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
mm/memory_hotplug.c | 58 -----------------------------------------------------
1 file changed, 58 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 599c675ad538..10052c2fd400 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -763,23 +763,6 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
return 0;
}
-#ifdef CONFIG_MOVABLE_NODE
-/*
- * When CONFIG_MOVABLE_NODE, we permit onlining of a node which doesn't have
- * normal memory.
- */
-static bool can_online_high_movable(int nid)
-{
- return true;
-}
-#else /* CONFIG_MOVABLE_NODE */
-/* ensure every online node has NORMAL memory */
-static bool can_online_high_movable(int nid)
-{
- return node_state(nid, N_NORMAL_MEMORY);
-}
-#endif /* CONFIG_MOVABLE_NODE */
-
/* check which state of node_states will be changed when online memory */
static void node_states_check_changes_online(unsigned long nr_pages,
struct zone *zone, struct memory_notify *arg)
@@ -979,9 +962,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
if (!allow_online_pfn_range(nid, pfn, nr_pages, online_type))
return -EINVAL;
- if (online_type == MMOP_ONLINE_MOVABLE && !can_online_high_movable(nid))
- return -EINVAL;
-
/* associate pfn range with the zone */
zone = move_pfn_range(online_type, nid, pfn, nr_pages);
@@ -1579,41 +1559,6 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
return offlined;
}
-#ifdef CONFIG_MOVABLE_NODE
-/*
- * When CONFIG_MOVABLE_NODE, we permit offlining of a node which doesn't have
- * normal memory.
- */
-static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
-{
- return true;
-}
-#else /* CONFIG_MOVABLE_NODE */
-/* ensure the node has NORMAL memory if it is still online */
-static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
-{
- struct pglist_data *pgdat = zone->zone_pgdat;
- unsigned long present_pages = 0;
- enum zone_type zt;
-
- for (zt = 0; zt <= ZONE_NORMAL; zt++)
- present_pages += pgdat->node_zones[zt].present_pages;
-
- if (present_pages > nr_pages)
- return true;
-
- present_pages = 0;
- for (; zt <= ZONE_MOVABLE; zt++)
- present_pages += pgdat->node_zones[zt].present_pages;
-
- /*
- * we can't offline the last normal memory until all
- * higher memory is offlined.
- */
- return present_pages == 0;
-}
-#endif /* CONFIG_MOVABLE_NODE */
-
static int __init cmdline_parse_movable_node(char *p)
{
#ifdef CONFIG_MOVABLE_NODE
@@ -1741,9 +1686,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
node = zone_to_nid(zone);
nr_pages = end_pfn - start_pfn;
- if (zone_idx(zone) <= ZONE_NORMAL && !can_offline_normal(zone, nr_pages))
- return -EINVAL;
-
/* set above range as isolated */
ret = start_isolate_page_range(start_pfn, end_pfn,
MIGRATE_MOVABLE, true);
--
2.11.0
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